SAVA KZN Branch Meeting, San Lameer, 21-22 May 2016 SAVA...

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SAVA KZN Branch Meeting San Lameer 21-22 May 2016 Petrie Vogel Tel: 012 346 0687 Fax: 012 346 2929 [email protected] Programme Saturday 21 May 2016 12:30 - 14:00 LUNCH AND REGISTRATION 14:00 - 15:00 Abdominal Biopsy Techniques Dr Sara Boyd 15:00 - 16:00 GIT Surgery - Ensuring no leaks Dr Sara Boyd 16:00 - 16:20 TEA BREAK 16:20 - 17:20 Choosing the right Diagnostic tests - FIV/FeLV/FIP Prof Andrew Leisewitz 17:20 - 18:20 Avoiding Common Pitfalls Dr Phil Rees et al CHILL TIME 19:30 - late DINNER AND ENTERTAINMENT sponsored by Ultra Dog Sunday 22 May 2016 07:00 - 09:00 BREAKFAST AND REGISTRATION 09:00 - 10:00 Diaphragmatic Hernia Management and Surgery Dr Sara Boyd 10:00 - 11:00 Antibiotic treatment of skin disease Prof Andrew Leisewitz 11:00 - 11:20 TEA BREAK 11:20 - 12:20 Otitis externa Prof Andrew Leisewitz 12:20 - 13:20 Canine Prostatic Disease Dr Daniela Steckler 13:20 - 15:00 LUNCH SAVA KZN Branch Meeting, San Lameer, 21-22 May 2016 1

Transcript of SAVA KZN Branch Meeting, San Lameer, 21-22 May 2016 SAVA...

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SAVA KZN Branch Meeting San Lameer

21-22 May 2016

Petrie VogelTel: 012 346 0687Fax: 012 346 [email protected]

ProgrammeSaturday 21 May 201612:30 - 14:00 LUNCH AND REGISTRATION

14:00 - 15:00 Abdominal Biopsy Techniques Dr Sara Boyd

15:00 - 16:00 GIT Surgery - Ensuring no leaks Dr Sara Boyd

16:00 - 16:20 TEA BREAK

16:20 - 17:20 Choosing the right Diagnostic tests - FIV/FeLV/FIP Prof Andrew Leisewitz

17:20 - 18:20 Avoiding Common Pitfalls Dr Phil Rees et al

CHILL TIME

19:30 - late DINNER AND ENTERTAINMENT sponsored by Ultra Dog

Sunday 22 May 201607:00 - 09:00 BREAKFAST AND REGISTRATION

09:00 - 10:00 Diaphragmatic Hernia Management and Surgery Dr Sara Boyd

10:00 - 11:00 Antibiotic treatment of skin disease Prof Andrew Leisewitz

11:00 - 11:20 TEA BREAK

11:20 - 12:20 Otitis externa Prof Andrew Leisewitz

12:20 - 13:20 Canine Prostatic Disease Dr Daniela Steckler

13:20 - 15:00 LUNCH

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SAVA KZN Branch Meeting San Lameer

21-22 May 2016

Petrie VogelTel: 012 346 0687Fax: 012 346 [email protected]

CV – DR S.M. BOYD

Dr Sara Boyd graduated in 1997 from Onderstepoort Veterinary Faculty with a BVSc. After graduating she went to England for 18 months where she worked in small animal private practice. In 1999 she was offered a position at Onderstepoort as a resident in the Department of Small Animal Surgery. She started her Masters degree in surgery and later became a senior lecturer at Onderstepoort, teaching both under graduate and post graduate students. She left Onderstepoort in September 2001 to join Dr Eugene Buffa at Johannesburg Specialist Veterinary Centre. She completed her MMVedVet degree in April 2004 and is currently a partner in this practice.

Johannesburg Specialist Veterinary Centre is one of the largest private specialist hospitals in South Africa with two qualified surgical specialists and one internal medicine specialist. It is currently a 7 vet hospital and is training both surgical and medical residents. Sara is involved in presenting continuing professional development courses both in South Africa and abroad. Her special interests lie in the field of soft tissue and neurosurgery. She is also one of the few South African veterinarians regularly performing Canine Cementless Total Hip Replacement. She is married to Mark Boyd and has 3 children: Jordan, Tyler and Aimee.

CV - Dr SM Boyd

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ABDOMINAL BIOPSY TECHNIQUES

Dr Sara Boyd, BVSC MMedVet (surg.)

Johannesburg Specialist Veterinary Centre, 63 Kayburne Avenue, Randpark Ridge, South Africa [email protected]

Introduction

Celiotomy is the correct terminology for a surgical incision into the abdominal cavity1. The lack of sophisticated equipment required makes celiotomy one of the most commonly used procedures for both therapeutic and diagnostic purposes. The most common approach is via a ventral midline incision; however paracostal and paralumbar approaches are also possible and are useful for limited exposure of specific organs like the kidneys or adrenal glands1. Regardless of the reason for opening the abdomen, the general principles of abdominal surgery should be adhered to whenever an invasive exploratory celiotomy is performed. When performed for diagnostic purposes, special care must be taken not to create additional problems for the animal, like causing haemorrhage, adhesions or introducing infection into the abdomen.

Liver

The cranial location of the liver may make taking liver biopsies difficult, especially in deep-chested dog breeds. The liver is also an extremely friable organ, especially in the presence of disease. Advanced liver disease may be associated with a decrease in clotting factors which can make intra-operative haemorrhage a risk and require a preoperative whole blood transfusion. Liver disease may also cause hypoalbulminaemia which leads to delayed wound healing. Blood protein levels and a full blood count prior to surgery, are an important part of pre-operative planning.

The liver consists of 6 relatively distinct lobes which usually have sharp edges and a uniform appearance to the parenchyma. Lobes may become rounded in very young animals or in animals with congested, scarred or infiltrated livers. Where possible, the left side of the liver should be biopsied, especially when using percutaneous techniques, in order to avoid damage to the biliary tree2,3.

Biopsy techniques include percutaneous methods (blind or ultrasound guided), laparoscopy or celiotomy. Percutaneous techniques are not recommended in animals with thrombocytopaenia, cavitatory or highly vascular lesions3,4,5. When direct visualization is used, the guillotine method is the most effective way of taking meaningful biopsies. Tru Cut or skin biopsy punches may also be used and are particularly useful for isolated lesions in the centre of one of the liver lobes3,4.Chromic cat gut in an appropriate size to combat breaking strength, is the most commonly used suture material. It is cost effective, readily available, has excellent knotting ability and is absorbed by phagocytosis once a fibrous ligation has formed.

In the case of far cranial liver lesions, large friable masses or in very deep-chested breeds, it may be useful to temporarily puncture the diaphragm and ventilate the patient. This allows the entire diaphragm to move caudally and in so doing, greatly increase exposure and accessibility of the liver lobes.

Stomach

It is advisable to withhold food for at least 8 to 12 hours prior to surgery on the stomach. 18 to 24 hours is recommended for gastroscopic biopsy techniques, where visualization is of utmost importance. In paediatric patients, hypoglycemia can be a problem and so starving is only advised for 4 to 6 hours in these patients6

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Surgery of the stomach has relatively little post-operative complications due to the good blood supply and reduced numbers of bacteria6,7. It also has close proximity to the omental defense mechanisms and rapidly regenerating epithelium. Unless a specific lesion has been identified in the stomach, biopsies should be taken from a hypovascular site along the ventral aspect of the stomach. Always avoid damage to the greater gastroepiploeic blood vessel that run along the ventral edge. The pyloric region should be avoided due to the risk of outflow obstruction occurring at a later stage. Where the lesion of interest occurs on the pyloric sphincter, incision may need to be adapted during closure of defect, to ensure that a stenotic, intraluminal section is not created. Stomach biopsy sites should be closed in two layers using a 3/0 or 4/0 monofilament, absorbable suture material. Atraumatic, swagged on needles are mandatory and easily affordable, even in general practice. Gentle pressure is the best way to stop any residual bleeding. Haemostatic aids like Surgicel (cellulose impregnated gauze swabs) can also be used, but are seldom necessary. Small Intestine The small intestine can be biopsied using endoscopic, ultrasonographic, laparoscopy techniques or surgically via a celiotomy. Endoscopic techniques allow good visualization of the mucosa and multiple biopsies can be taken, but biopsies are not full thickness and biopsy of the jejunum is rarely possible6,7. Celiotomy, on the other hand, allows examination of the entire gastrointestinal tract as well as all other abdominal organs. Multiple, full thickness biopsies are possible, but direct visualization of the mucosa is not. When performing surgical biopsies of the small intestine, multiple biopsies should be taken. A scalpel, Metzenbaum scissors or a skin biopsy punch can be used. The skin punch biopsies are a very effective technique which provides full thickness, good quality sample and defects that are easy to close. Longitudinal biopsies may be closed in a transverse direction to prevent a decrease in diameter of the intestinal lumen. Omentum is gently wrapped over the biopsy site prior to abdominal closure. Haemostatic agents are almost never required. Spleen The spleen is usually biopsied in order to diagnose causes of splenomegaly or infiltrative or neoplastic disease. Percutaneous techniques are effective for the diagnosis of diffuse disease like mastocytosis or lymphoma. Cavitatory lesions should not be attempted using this method, as these may rupture and this could have fatal consequences. When surgical biopsy is required, we use similar techniques to those used in the liver: guillotine method or overlapping, horizontal mattress sutures are used to obtain a wedge or oval shaped biopsy sample. In cases of large tumours or diffuse disease, it may be easier and less risky to perform a total splenectomy. Pancreas Pancreatic tissue needs to be handled with extreme care at all times to prevent pancreatitis, adhesions or oedema from occurring. Having said that, the pancreas is easily accessible and should not be avoided if gross abnormalities are present. Biopsies are taken more commonly in feline patients, as pancreatic disease in this species is more difficult to diagnose than in dogs. Both limbs of the pancreas should be examined and if necessary biopsied. The easiest region to sample is the caudal aspect of the right limb. Samples should be taken from the edge of the pancreas. Tru Cut tissue core biopsy needles can also be used to gain a suitable sample and this can be done using ultrasound guidance, but direct visualisation is preferred due to proximity of other organs and vital vasculature.

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Colon Surgery of the colon carries the risk of more complications than does the rest of the GIT, due to the fact that it contains more bacteria and has a significantly poorer blood supply7. Principles of colonic surgery include causing minimal damage to the blood supply and making sure that each suture is precisely tied and includes the submucosal layer. Surgical sites should be wrapped in omentum prior to closure of the abdomen and surgical sets should also be changed prior to closure of the abdomen. Where possible, full thickness biopsies should be avoided and for this reason, colonoscopy with multiple mucosal biopsies is the preferred diagnostic technique. Bladder Biopsy of the bladder is relatively easy. Stay sutures should be used in the apex of the bladder to make manipulation less traumatic and to minimize spillage. Draining the bladder prior to perforation is useful to decrease abdominal contamination. Biopsy samples can be taken from the dorsal or ventral aspect of the bladder. A stab incision is made into the bladder lumen and then slices are taken from the edge of the incision prior to closure. Specific areas of thickening or discoloration should be targeted. 3/0 or 4/0 absorbable, monofilament suture material is recommended and used in a continuous fashion in order to close the bladder. Performing a leak test is easy and cost effective and may help pin point potential weak spots in the suture line. Prostate Occasionally it may be necessary to biopsy the prostate. This is best achieved via a ventral abdominal midline or paramedian incision. A catheter should always be preplaced in the urethra, so that this structure is avoided during biopsy taking. A wedge shaped biopsy is removed from the ventrolateral parenchyma and capsule can be over sewn with absorbable suture material to decrease haemorrhage. It is often indicated to drain concurrent cysts that may be adding to the dog’s discomfort and ease of urination. Mesenteric lymph nodes Where possible, at least two nodes from the area of interest should be taken. If large enough, Tru Cut or fine needle aspirate techniques can be used, but wedge biopsies under direct visualisation are preferred. Horizontal mattress sutures can be preplaced through the lymph node and then a 15 scalpel blade used to cut a suitable wedge. Alternatively, perform a complete lymphadenectomy. Kidney The kidneys lie in the retroperitoneal space. The right kidney lies at the level of the thirteenth rib whilst the left kidney lies approximately 5cm caudal to the last rib. Biopsies must always include as much of the renal cortex as possible, as samples containing the renal medulla are seldom diagnostic5. Biopsy techniques used include: percutaneous methods (of which ultrasound guided techniques are preferred), laparoscopy, surgery or keyhole abdominal surgery techniques. Automated biopsy devices or Tru Cut needles may be used in the latter two techniques. Alternatively wedge biopsies are performed. In this last technique, mattress sutures are placed deep to biopsy site and when tied include a piece of omentum into the incision. This prevents bleeding and helps prevent sutures from pulling out of the very friable kidney capsule. Once again, haemostatic agents like Surgicel should be on standby. Adrenal Glands These glands are usually removed in their entirety when involved in disease processes and seldom if ever are biopsied. Generally surgeons should try and stay outside the capsule of the adrenal glands, especially when neoplasia is suspected, as leaving small pieces behind in the abdomen

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may lead to tumour seeding. This surgery can be technically difficult due to local fat deposits (most of affected patients are excessively fat due to the cortisol production) and vascular structures associated with the glands. Some key tips that help with exposure and resection are: to always have a scrubbed assistant, to have adequate abdominal swabs available to help with isolation of the gland, to perform a paracostal incision to increase exposure and to tie off the associated phrenicoabdominal blood vessels with courses directly over the adrenal gland, before attempting blunt dissection. Conclusion On the whole, biopsy techniques are an extremely useful means of obtaining a definitive diagnosis. They form an essential tool in diagnostic medicine and surgeons need to be proficient in the various techniques. As long the basic surgical principles are adhered to, the techniques are safe and the tips provided in this paper should make taking full thickness, good quality biopsies simple and affordable. References:

1. Fossum TW. Surgery of the abdominal cavity. In: Fossum TW, Dewey CW, editors. Small Animal Surgery. 4th ed. Missouri: Elsevier Mosby: 356-385; 2013.

2. Radlinsky MG. Surgery of the liver. In: Fossum TW, Dewey CW, editors. Small Animal

Surgery. 4th ed. Missouri: Elsevier Mosby: 584-617; 2013.

3. Cardi M, Mutillo IA, Amaderi L, et al. Superiority of laproscopy compared to ultrasonography in diagnosis of widespread liver disease. Dig Dis Sci 42: 546, 1997.

4. Cole TL, Centre SA, Flood SN, et al. Diagnostic comparison of needle and wedge biopsy

specimens of the liver in dogs and cats. J Am Vet Med Assoc 220: 1483, 2002.

5. Rawlings CA, Howerth EW. Obtaining quality biopsies of the liver and kidney. J Am Vet Med Assoc 40: 352, 2004.

6. Radlinsky MG. Surgery of the digestive system. In: Fossum TW, Dewey CW, editors. Small Animal Surgery. 4th ed. Missouri: Elsevier Mosby: 339-497; 2013.

7. Tobias KM Johnston SA. Veterinary Surgery Small Animal vol.2. Digestive System. Missouri: Elsevier Saunders: 1425-1690; 2012.

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GASTROINTESTINAL TRACT SURGERY - AVOIDING LEAKS

Dr Sara Boyd, BVSC MMedVet (surg.)

Johannesburg Specialist Veterinary Centre, 63 Kayburne Avenue, Randpark Ridge, South Africa

[email protected]

Introduction The possibility of complications occurring with gastrointestinal (GI) surgery is a very real threat to surgeons, regardless of their level of expertise. In fact, it is amazing that the gastrointestinal tract (GIT) is able to heal at all. There is constant motion, the lumen contains fluid and there is food, bacteria and enzymes in contact with the incision at all times. The reason that the GIT is able to heal so well is that it has a profuse vasculature, rapidly regenerating epithelium and a natural defence mechanism provided by the omentum1. Celiotomy refers to a surgical incision into the abdominal cavity. Regardless of the reason for the procedure, general principles of abdominal surgery should be adhered to whenever an invasive exploratory celiotomy is performed. The most common approach to the abdomen is via a ventral midline incision. A ventral midline incision can extend from lateral to the xiphoid process to ventral to the pubic symphysis. The superficial epigastric vein can be clamped and ligated to improve exposure2. The three principle sections of the GIT that will be discussed are the stomach, small intestine (SI) and large intestine (LI). Four anatomical layers form the GI tube: the mucosa, submucosa, muscularis externa and serosa. The blood supply to the GIT is provided by the mesenteric arteries which penetrate the GI wall and then split into three arteriovenous plexuses. Dehiscence usually occurs somewhere between 72 to 96 hours after wound creation. This period is known as the “lag phase” of GIT healing and is the most critical period3. Dehiscence leads to spillage of GI contents into the abdomen with resulting peritonitis and the consequences of this may be fatal. It can be avoided by choosing the correct size and type of suture material, catching sufficient amounts of the correct adjacent tissues and by tying careful, surgically correct knots. The role of the omentum is vital in GIT surgery. It plays a major role in sealing GI wounds; it helps restore blood supply, controls infection and facilitates good drainage. Pedicle omental grafts are preferred over free grafts, as these tend to discourage adhesion formation. Ideally omentum should be wrapped or sutured (not usually necessary) around all GI incisions prior to closure of the abdomen4. Stomach The stomach has the thickest wall of any of the sections of the GIT. It is extremely vascular and avoiding unnecessary damage to the vasculature, is important. Because of this rich blood supply and low bacterial numbers, most incisions into the gastric wall will heal despite the surgical technique used. The suture technique of choice is a double layer, continuous inverting pattern like the Cushing or Lembert1. The first layer is placed in the mucosa / submucosa and the second in the seromuscular component. Monofilament, absorbable suture material is advocated and suture line ulcers have been reported when non-absorbable suture material was used7.

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Small Intestine Healing of the SI occurs optimally when there is direct apposition of the layers of the intestinal wall. This allows the submucosal arteriovenous plexuses to align and reepithelialisation can occur within 3 days without compromising the diameter of the lumen. Mucosal eversion and tissue overlap retard reepithelialisation by causing mucosal ischaemia and necrosis5. Further complications of this are increased inflammation, intestinal stenosis and formation of abdominal adhesions. There will also be a decrease in bursting strength and therefore an increased incidence of dehiscence and leakage3,5,6. Trimming the excess mucosa and ensuring that there is no debris on the cut edges prior to anastomosis, decreases the chance of leakage5,6. Various suture patterns have been described and tested in the SI. These include simple interrupted, modified Gambee or simple continuous patterns. Crushing verses non-crushing techniques have also been described. Results are fairly similar between all of these; however crushing techniques have been shown to cause more micro trauma and necrosis. Knots should be tied securely and should remain on the extraluminal side of the GI tube7. A useful technique is to angle the needle so that the serosal surface is engaged slightly further from the edge than the mucosal suture. Prior to closing the abdomen, leakage tests using sterile saline are recommended and surgeons should then also wrap the anastomosis site in omentum4. Serosal patching is a technique that consists of placing the anti-mesenteric border of an adjacent loop of intestine over a suture line in the GIT and securing this to it with sutures. The aim of this procedure is to provide the damaged section with a fibrin seal, blood supply, support and a barrier against leakage. The use of serosal patching is recommended whenever viability is questionable or if dehiscence has already occurred. Kinking of the adjacent intestinal loops should be avoided when using this technique1,8. Large Intestine (Colon) The colon demonstrates the same mechanisms of healing that occur in the stomach and SI, however the entire process is delayed. Morbidity and mortality rates in the colon are higher due to the following reasons: colonic circulation is poor, the blood supply is segmental, the population of bacteria is high and the faeces place additional mechanical strain on the incision sites1,8. A further disadvantage is that the omentum rarely reaches that far caudally4. The risk of early incisional dehiscence is high in the colon. Effective means of counteracting some of these problems are to eliminate faeces using enemas at least 24 hours before the procedure, use effective antibiotic protocols and practice good serosal apposition. The holding layer for the colon is also the submucosal layer and the recommended suture pattern is a simple, interrupted, appositional pattern or a modified Gambee7. The sutures should be placed 3 to 4 mm apart and 2 to 3mm from the cut edge. Using commercial end-to-end anastomosis staple guns are also an effective, but expensive technique to close colonic incisions1,8. Possible Complications Dehiscence and the resulting peritonitis are extremely severe consequences to surgery of the GI system. Peritonitis is the inflammation of the peritoneum, which may be primary or secondary and infectious or non-infectious. Post surgical peritonitis is the most common type and is typically classified as secondary and infectious2. The three main causes of dehiscence include pre-existing intestinal trauma, pre-existing peritonitis or hypoalbuminaemia. Peritonitis is suspected when the abdominal effusion contains intracellular bacteria, when spontaneous extraluminal gas bubbles are present on radiographs or when the peritoneal effusion contains more than 25 000 neutrophils per microliter. The goals of treatment of peritonitis include most importantly, isolating and removing the source of the contamination, resolving the infection

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and restoring the normal fluid and electrolyte imbalances2,8. Surgery is indicated when the cause of the contamination cannot be found or when bowel rupture is suspected. Lavage with sterile intravenous fluid is indicated in animals with diffuse peritonitis, but should be used with caution in localised cases in order to prevent dissemination of the infection. Despite aggressive therapy, the prognosis for peritonitis remains guarded and so, as in many surgical cases, prevention is better than cure. Conclusion The gastrointestinal tract will usually heal without complications provided atraumatic techniques are used, tissue viability is preserved and contamination is minimised. Adhering to basic principles and using due diligence when suturing, can result in complications being minimised and surgical success rates, improved. Post operative monitoring of the patient can further improve success rates by picking up any potential complications as early as possible and correcting them before the animal becomes too debilitated. Recommended Reading

1. Radlinsky MG. Surgery of the digestive system. In: Fossum TW, Dewey CW, editors. Small Animal Surgery. 4th ed. Missouri: Elsevier Mosby: 339-497; 2013.

2. Fossum TW. Surgery of the abdominal cavity. In: Fossum TW, Dewey CW, editors. Small

Animal Surgery. 4th ed. Missouri: Elsevier Mosby: 356-385; 2013.

3. Allen DA, Smeak DD, Schertel ER. Prevalence of small intestinal dehiscence and associated clinical factors: A retrospective study of 121 dogs. J Am Anim Hosp Assoc 28: 70-76, 1992.

4. McLackin AD, Denton DW. Omental protection of intestinal anastomosis. Am J Surg 125:

134-140, 1973.

5. Blikslagen AT, Roberts MC. Mechanisms of intestinal mucosal repair. J Am Vet Med Assoc 211: 1437-1441, 1997.

6. Coolman BR, Ehrhart N, Maretta SM. Healing of intestinal anastomoses. Comp Cont Edu

22: 363-371, 2000.

7. Weisman DL, Smeak DD, Birchard SJ, et al. Comparison of a continuous suture pattern with a simple interrupted pattern for enteric closure in dogs and cats: 83 cases. J Am Vet Med Assoc 214: 1507-1510, 1999.

8. Tobias KM Johnston SA. Veterinary Surgery Small Animal vol.2. Digestive system. Missouri: Elsevier Saunders: 1425-1690; 2012.

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The Diagnosis of Feline Retroviral and Carona-viral diseases Major ref: Canine and feline infectious diseases, Elsevier Saunders, 2014, Ed J E Sykes.

Caronavirus Diagnosis Currently, definitive diagnosis of FIP is made only by immunohistochemical staining for coronavirus antigen within lesions characterized by pyogranulomatous or granulomatous vasculitis. Because it can be difficult or impossible to safely obtain biopsy specimens from cats with FIP, antemortem diagnosis is often only suspected on the basis of history, signalment, and clinical and laboratory findings, and by ruling out other causes of disease. Provided it is correctly performed and interpreted, immunocytochemistry may be helpful. Because the presnce of the characteristic effusion is most helpful for antemortem diagnosis, efforts should be always made to identify and analyze any fluid that is present in body cavities. When owner funds are limited, laboratory analysis of effusion, rather than blood, may be the most economic diagnostic approach. Unfortunately, the lack of a definitive noninvasive diagnostic assay for FIP and the extremely poor prognosis sometimes leads clinicians to perform large numbers of diagnostic tests in the hope that an answer will appear. In other situations, the diagnosis of FIP is made too hastily, and euthanasia is performed without sufficient clinical and laboratory justification

Laboratory diagnosis Complete blood count A mild, nonregenerative anemia is often present in cats with FIP, and sometimes severe anemia occurs, which is usually poorly regenerative or nonregenerative (Table 20-1). Microcytosis may be present. Examination of erythrocyte morphology occasionally reveals schistocytosis, mild normoblastosis, or agglutination. There may be a leukocytosis due to a neutrophilia and monocytosis, or leukopenia. Lymphopenia occurs in more than 50% of affected cats, and eosinopenia is also common. In some cats, a left shift and evidence of toxic neutrophils are seen. Mild to moderate thrombocytopenia is common in cats with noneffusive disease and may reflect the presence of disseminated intravascular coagulation or immune-mediated platelet destruction. However, thrombocytosis can also occur

Serum biochemistry Many cats with FIP have hyperproteinemia due to hyperglobulinemia, which results from a polyclonal gammopathy (Figure 20-6). Rarely, a monoclonal gammopathy can occur. Total protein concentrations may be as high as 12 g/dL (Table 20-2). In one study, hyperglobulinemia was present in 50% of cats with effusion and 70% of cats without effusion. Globulin concentration may decrease terminally, so cats with advanced disease may have protein concentrations that are within the reference range. Hypoalbumin emia is often present because of liver involvement, leakage from damaged vessels, urinary loss in cats with glomerulonephritis, or inflammation (albumin is a negative acute-phase protein). Thus, the serum albumin:globulin ratio may be more useful than the globulin alone for diagnosis; ratios less than 0.8 are uncommon (but not impossible) in cats with

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FIP, so they help to rule out (but not to rule in) a diagnosis of FIP. Other variable findings include hyponatremia, hypokalemia, hypochloremia, hyperglycemia, azotaemia, increased liver enzyme activities, hypocholesterolemia, and hyperbilirubinemia. The cause of hyperbilirubinemia is not clear, but it may result from hemolysis, hepatic necrosis, and/or cholestasis. Measurement of α1-acid glycoprotein (an acute phase protein) has been suggested for diagnosis, because serum concentrations often exceed 1500 pg/mL in cats with FIP. However α1-acid glycoprotein concentrations also increase with other inflammatory diseases

Urinalysis The urinalysis in cats with FIP may be unremarkable or contain protein due to glomerular or tubular damage. Hematuria and, less commonly, pyuria and cylindruria may be present. Bilirubi nuria may be detected in cats with liver injury.

Coagulation profile In addition to thrombocytopenia, abnormalities of coagulation in cats with FIP include prolonged prothrombin time and partial thromboplastin time as a result of severe liver injury, and increased fibrin degradation product or D-dimer concentrations. Analysis of fluid The "classic" FIP effusion fluid is a high-protein (greater than 3.5 g/dL) exudate that contains a low number of nucleated cells (<5000 cells/µL), usually nondegenerate to mildly degenerate neutrophils and macrophages (Table 20-3 ). Erythrophagocytosis, leukophagia, and reactive mesothelial cells can be observed in the fluid from some cats. Grossly, the fluid has a yellow appearance and may contain fibrin clots. However, the total protein content and cell counts of abdominal and pleural effusions vary considerably, which complicates the diagnosis for some cats with effusive disease. Very rarely, chylous effusions occur. An effusion albumin/globulin ratio below 0.4 is suggestive of FIP. The Rivalta test is a simple test that can differentiate between transudates and exudates. In this test, a drop of 98% glacial acetic acid is mixed with 7 to 8 mL of distilled water in a transparent 10-mL tube. A drop of effusion is then added to the tube, and if it dissipates in the solution, the test is negative. If it retains its shape, stays attached to the surface, or moves slowly down in the solution, then the test is positive. In a study of cats with effusion, 35% of which had FIP and a conclusive Rivalta test, the positive predictive value of this test for the diagnosis of FIP was 58% (58% chance that a cat that tests positive truly has FIP), and the negative predictive value was 93% (93% chance that a cat that tests negative does not have FIP). In younger cats, the positive predictive value of the test is higher, because diseases such as lymphoma and bacterial peritonitis are less common. Positive test results indicate only the presence of an exudate, so cytologic examination of the fluid must still be performed. Cerebrospinal fluid analysis The cerebrospinal fluid (CSF) of cats with neurologic FIP often has increased protein content (30 to more than 1000 mg/dL, reference range less than 25 mg/dL) and increased total nucleated cell count (20 to 10,000 cells/J.IL), usually consisting of a mixed but predominantly neutrophilic cellular pleocytosis (Table 20-4). In some cats, protein content and leukocyte counts are normal.

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Table ref: Canine and feline infectious disease, Ed: J E Sykes, 2014 pp 199.

Table ref: Canine and feline infectious disease, Ed: J E Sykes, 2014 pp 200.

Diagnostic imaging Plain radiography Plain thoracic radiography may reveal pleural effusion, enlargement of the cardiac silhouette in cats

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with pericardial effusion, and pulmonary nodular or peribronchial infiltrates in cats with pyogranulomatous pneumonia. Abdominal radiographs may show loss of peritoneal or retroperitoneal detail du e to peritoneal effusion, hepatomegaly, splenomegaly, renomegaly, or mass lesions associated with the gastrointestinal tract or abdominal lymph nodes. Ultrasongraphy Abdominal ultrasound findings in FIP include the presence of anechoic or mildly echogenic peritoneal fluid; hyperechogenicity and "clumping" of the mesentery; enlarged and hypoechoic abdominal lymph nodes; enlargement and diffuse or focal hypoechogenicity of the liver and spleen; renal asymmetry with increased cortical echogenicity, hypoechoic nodules, subcapsular fluid accumulation, or loss of corticomedullary distinction; and/or thickening of all intestinal wall layers or intestinal mass lesions . Pleural effusion may be seen through the diaphragm. MRI of the CNS Findings on MRI that suggest FIP consist of ventricular dilatation and variable contrast enhancement of the periventricular regions, choroid, and meninges. In some cats, MRI findings are unremarkable. Microbiological testing Serological testing Detection of antibodies to FCoV can be performed using immunofluorescent antibody testing, ELISA, or virus neutralization. The methods used, as well as the titers themselves, vary considerably between laboratories. For example, some laboratories use related coronaviruses as a source of antigen for the test, rather than FCoV. Use of a reliable laboratory that reports qu antitative titers (to the endpoint dilution, as well as down to 1:100) is critical. Even when performed correctly, a positive FCoV antibody titer is not diagnostic for FIP, because cats that have been exposed to avirulent FCoV strains or even other related coronaviruses are also seropositive. Therefore, serology is a "coronavirus antibody test" and not an "FIP test." It has been suggested that more cats have been killed as a result of misinterpretation of FCoV antibody tests than by the disease itself. Certainly a diagnosis of FIP should never be made based on the presence o f n o n s p e c i f i c c l i n i c a l or laboratory a b n o r malities such as fever or leukocytosis and a positive coronavirus antibody test. Occasionally (up to 10% of the time), cats with advanced disease are seronegative, because of failure of antibody production with severe immunosuppression, or the complexing of antibody by the large quantities of virus present. In one study, titers of 1:1600 or higher were highly suggestive (94% chance) of FIP in the presence of compatible clinical signs. In addition, strong positive titers (e.g., 1:6400) in cats with consistent signs and laboratory abnormalities support a diagnosis of FIP if a cat resides in a household that contains only one or two cats, because cats often become seronegative within a few months once they are removed from households that contain large numbers of cats. Other body fluids can also be analyzed for antibodies to FCoV. In one study, positive antibody titers in effusion had a positive predictive value of 90% and a negative predictive value of 79%, but the magnitude of the titer did not correlate with the diagnosis of FIP. The presence

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of anti-FCoV antibody in the CSF correlated well with a diagnosis of FIP in one study, but not in another study. In addition, the presence of sufficient quantities of CSF for serology are frequently not available. Molecular diagnosis using PCR Real-time reverse transcriptase -PCR (RT-PCR) assays have been developed for detection of FCoV, but these do not differentiate between virulent and avirulent strains. In addition, avirulent strains can be found in the blood and tissues of cats that do not have FIP, so the finding of virus in locations other than the gastrointestinal tract is not helpful for diagnosis. False negative test results can occur when there are low quantities of virus present or if degradation of RNA occurs during specimen transport. Some RT-PCR assays do not detect all strains of FCoV. Positive RT-PCR results in blood or effusion fluid from cats with other clinical abnormalities that suggest FIP do indicate the presence of a coronavirus and, in that respect, may help to support the diagnosis made, provided the limitations of the test are recognized. Immunostaining for FeCV antigen FeCoV antigen can be detected in macrophages with immunocytochemistry or immunohistochemistry. Either fluorescent a n t i b o d y or immunoperoxidase methods may be used. When antigen tests are positive, provided the test is performed and interpreted properly (with use of positive and negative control slides), studies suggest that only cats with FIP have positive test results. False- negative results occur when there are insufficient numbers of infected cells, when low quantities of virus are present, or when antigen is unavailable for detection because of complexing by antibody.

FeLV Diagnosis Infection with FeLV is often diagnosed when healthy cats are screened for infection. Screening should be performed with ELISA or related immunochromatographic in-house assays for free FeLV antigen in serum, because these assays are sensitive, specific, rapid, widely available, and most well understood. The retrovirus status of all cats should be known regardless of the presence of absence of illness. Even though many cats that test positive for FeLV antigen have no clinical signs or physical examination abnormalities, a CBC, chemistry panel, and urinalysis should be obtained from these cats (and at a minimum, a complete CBC with blood smear evaluation) to assess for underlying abnormalities that could signal the presence of FeLV -related disorders. Subtle hematologic abnormalities, such as erythroid macrocytosis or monocytopenia, may be present in the absence of overt clinical signs and can signify a poorer long-term outcome. Additional diagnostic tests indicated in infected cats that are anemic include a reticulocyte count, Coombs' test, and PCR assay for hemoplasmas. Bone marrow aspiration and core biopsy are indicated in cats with pancytopenia or persistent nonregenerative anemias.

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Laboratory Abnormalities Complete Blood Count The CBC may be normal or show regenerative or nonregenerative anemia, neutropenia, lymphopenia, monocytopenia, and/ or thrombocytopenia. Evidence of agglutination may be present in cats with IMHA. Moderate to marked leukocytosis and increased band neutrophils may also be present. Large numbers of circulating blasts, megakaryocytes or dysplastic cells (such as erythrocytes with giant Howell -Jolly bodies) can be found in cats with leukemia or MOS. When compared with uninfected cats, FeLV-infected cats were nearly 3.8-fold more likely to be anemic, 5-fold more likely to be thrombocytopenic, 3.6-fold more likely to be neutropenic, and 2.8-fold more likely to have lymphocytosis.

Serum Biochemical Tests and Urinalysis Findings on serum biochemistry analysis and urinalysis are nonspecific and reflect underlying disease processes. Hyperbilirubinemia and bilirubinuria may be present in cats with immune-mediated hemolyt ic anemia or hemoplasmosis . Cats with glomerulonephritis may be proteinuric. Some cats have evidence of bacterial urinary tract infections. Urine culture and susceptibility testing of a urine specimen obtained via cystocentesis are indicated in cats with suspected urinary tract infection

Bone Marrow Cytology and Histopathology Both bone marrow aspirate and core biopsy specimens should be obtained in cats with pancytopenia or nonregenerative anemia. If aspirate results are not diagnostic , the core biopsy should be submitted for interpretation. This is because bone marrow aspirates from cats with aplastic anemia or myelofibrosis are typically of low cellularity. Bone marrow findings in cats with FeLV infection include evidence of neoplastic lymphoid , erythroid, or myeloid cells (which circulate in the peripheral blood of cats with leukemia); myelodysplasia; hypoplasia or aplasia of erythroid, myeloid, or megakaryocyte cell lines; erythroid, myeloid, and megakaryocyte hyperplasia despite peripheral cytopenias; and megakaryocyte hypoplasia.

Diagnostic Imaging Imaging findings in cats with FeLV infection reflect the underlying disease process and are extremely variable. Cats with FeLV-associated thymic lymphosarcoma have a mediastinal mass on thoracic radiography that may be accompanied by mild to severe pleural effusion. Abdominal sonography in cats with multicentric lymphoma may reveal hypoechoic and enlarged abdominal lymph nodes and enlargement, hypoechogenicity, or mottling of the spleen, liver, or kidneys. Increased hepatic echogenicity can also occur with lymphoma. Intestinal masses with loss of normal bowel wall layering may also be detected. Splenomegaly may be detected in cats with immune- mediated cytopenias

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Microbiologic Tests Antigen Assays The initial assay of choice for diagnosis of FeLV infection is an ELISA or a similar immunochromatographic test that detects soluble p27 capsid protein antigen in blood. The term soluble is used to distinguish these assays from assays such as IFA, which detect fixed antigen within cells. In most cats, the presence of circulating antigen correlates with viremia, although a few cats have viremia in the absence of detectable antigen or antigenemia in the absence of detectable viremia.

In-practice lateral flow assays are available that detect antigen in anticoagulated whole blood, plasma, or serum. In the past, the use of whole blood generated less reliable results than when plasma or serum was used, but with new-generation tests, whole blood is considered an acceptable alternative.

When a choice is available, serum is the preferred specimen. The use of tears or saliva is not recommended, because errors are more likely to occur. When ELISAs are used as screening tests, confirmation of po sitive test results is recommended because of the low prevalence of infection in healthy cats and the higher possibility that false-positive test results may occur. Positive test results in the absence of FeLV antigen have the potential to occur rarely as a result of operator error or nonspecific reactivity. As for FIV infection, it is especially important to immediately confirm positive test results if they are likely to result in euthanasia or rehoming for disease control purposes. There are several options to confirm a positive test result:

• Perform another ELISA antigen test using an assay from a different manufacturer. However, it should be remembered that in contrast to FIV infection, cats that test truly positive for FeLV antigen early in the course of infection (i.e., before involvement of the bone marrow) may ultimately control the infection. Thus a single positive test result does not imply progressive infection, even if it is immediately repeatable using a test from a different manufacturer. If the cat has signs consistent with FeLV-related disease, a single positive test result is more likely to mean that progressive infection is present

• Perform an IFA assay on peripheral blood smears, because cats with positive IFA results have infection of the bone marrow and, with rare exceptions, are almost always progressively infected. Cats that test negative with IFA assays may be in a transient viremic phase that may result in either progressive or regressive infection, or they may have progressive infection but the sensitivity of IFA is too low to detect it. In this case, both ELISA and IFA assays, or the ELISA assay alone, could be repeated in 1 to 4 months. Retest with ELISA 6 months later. If the antigen test remains positive, progressive infection is likely. In some cats, antigenemia persists for 16 weeks before regression occurs, so the test could be repeated earlier than 6 months (e .g., 12 weeks later) or monthly if client finances permit so long as the cat remains healthy.

• Perform a full CBC. If hematologic abnormalities are present, progressive infection is likely.

Negative ELISA results can occur in the first month after exposure to FeLV, before sufficient antigen is detectable in the peripheral blood. Cats that test negative within 30 days of possible exposure to the virus should be retested 1 to 2 months later. Because development of antibodies to FIV can take

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up to 2 months, it is usually most practical to retest for both viral infection s 2 months after possible exposure. Kittens can be tested at any time, because maternal antibody does not interfere with FeLV testing.

Immunofluorescent Antibody or Immunoperoxidase staining IFA assays are widely offered by veterinary diagnostic laboratories and can be performed on fresh peripheral blood or bone marrow. At least two fresh smears (without anticoagulant) should be air-dried and mailed to the laboratory. IFA is less sensitive than ELISA and, depending on the laboratory, is more prone to false-negative and false-positive results and so is not recommended for screening purposes. The presence of detectable virus using IFA in circulating blood cells indicates progressive infection more than 90% of the time. Cats with early viremia (before the bone marrow is infected) test IFA-negative but ELISA-positive. Cats with regressive infection test negative with both IFA and ELISA assays. Negative IFA test results can occur in cats with progressive infection when there are inadequate blood cells in the periphery, such as in neutropenic cats. Performing IFA on bone marrow rather than peripheral blood may help to overcome this problem. False-positive results can occur when inexperienced laboratory personnel interpret nonspecific fluorescence as a positive test result. Some cats with clinical abnormalities that strongly suggest FeLV-related disease (such as leukemia or myelodysplasia ) test negative for circulating antigen using ELISA but have bone marrow cells that test positive for FeLV antigen using IFA. For example, in one small study, 8 of 18 cats with leukemia or MDS that tested negative for soluble FeLV antigen had bone marrow smears that were positive using IFA; the remainder tested IFA negative. This phenomenon may reflect either false-positive IFA assay results, or true infection with undetectable levels of antigen in the peripheral blood. The use of PCR on bone marrow may help to resolve the FeLV status in at least some of these cats Immunohistochemistry can also be used to detect viral antigen in tissue specimens or bone marrow core biopsies, although it may be less sensitive than IFA.

Molecular diagnosis using PCR Several different PCR assays have been developed for detection of FeLV nucleic acid. Currently the major clinical indications for PCR are (1) to screen potential blood donors in conjunction with antigen testing or (2) to test for regressive infection when FeLV is strongly suspected as the cause of neoplasia but antigen tests are negative. PCR assays may detect FeLV RNA (reverse transcriptase polymerase chain reaction [RT-PCR]) or proviral DNA and must be carefully designed so that they do not detect endogenous FeLV sequences. At the current time, PCR assays should never be used in the absence of antigen testing in order to screen for or diagnose FeLV infection. The clinician needs to understand if the assay used detects proviral DNA, viral RNA, or both (some laboratories run both assays), because the clinical significance of a positive viral RNA assay (i.e., productive viral infection) differs from that of a positive proviral DNA assay (which suggests nonproductive viral infection for cats with negative

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antigen tests). After infection, RT-PCR assays may be positive several weeks before antigen tests or virus isolation become positive, and depending on the assay, PCR for viral RNA can be more sensitive than soluble antigen tests. High viral RNA loads in blood and saliva appear to be associated with progressive infection, whereas low loads may be associated with regressive infection.

PCR assays for proviral DNA can be used on blood, buffy coats, bone marrow, or tissues of cats that test negative for FeLV antigen. Cats with a positive proviral PCR test result but negative soluble antigen test, which in one study represented about 10% of cats with negative antigen test results, have regressive infection. These cats are probably not infectious to other cats but may reactivate virus shedding with severe stress or immunosuppression, or transmit the virus through blood transfusion or vertical transmission. Proviral DNA appears to be present at much lower levels in cats with regressive infection than in those with progressive infection. The use of bone marrow or tissue specimens, rather than whole blood, may increase sensitivity for detection of proviral DNA Because FeLV vaccine virus is inactivated or recombinant, it does not replicate or integrate into the host genome, so vaccination should not lead to false-positive PCR results.

Diagnostic assays available for FeLVAssay Specimen type Target Performance ELISA or similar immuno - chromatographic tests for soluble FeLV antigen

Serum, plasma, wholeblood

FeLV p27 antigen Confirmation of positiveresults is recommended in healthy cats with a second test from a different manufacturer. Positive antigen test results do not signify progressive infection, and the assay must be repeated in 1to 3 months or an IFA performed. False negatives can occur in the first month of infection

IFA Serum, bone marrow FeLV antigen inblood cells

Less sensitive than ELISA.Positive results indicate infection of the bone marrow and therefore progressive infection. False positives may occur if nonspecific fluorescence is interpreted as a positive result.

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PCR Blood, bone marrow, saliva (RT-PCR); Marrow, tissue, lymph node aspirates (PCR)

FeLV RNA (RT-PCR) orproviral DNA bone

Sensitivity and specificitymay vary between laboratories. Never use in the absence of antigen testing. Assays that have demonstrated sensitivity and specificity may be useful to detect cats with regressive infection for elimination from blood donor programs, or to resolve the results of discordant ELISA and IFA assays. False-negative test results may occur when var ant strains are present.

Virus isolation Blood, marrow Replication competent FeLV virus

Difficult, not widely available. Requires a specialized laboratory. Used primarily as a research tool.

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Feline Immunodeficiency Virus Diagnosis For many cats, infection with FIV is diagnosed during screening efforts. Screening for infection should be performed with tests that detect antibody against FIV, because these assays have the highest overall sensitivity and are rapid and widely available. It has been recommended that the retrovirus status of all cats be known regardless of the presence of absence of illness. Indications for testing as recommended by the American Association of Feline Practitioners (AAFP) are shown below. In practice, compliance with retrovirus testing is low. In a study that evaluated 967 cats with bite wounds or cutaneous abscesses that presented to veterinary practitioners from 134 practices in 30 states, the combined FeLV-FIV status of only 96 (9.9%) of the cats was known. In addition , despite the availability of a financial incentive for retesting, only 64 of 478 cat owners returned their cats for retesting after treatment. When positive test results occur in sick cats, the role that FIV plays as a cause of the signs may be unclear, although it is reason able to assume that FIV may be playing a role in cats with severe stomatitis, unusual infections with intracellular pathogens such as mycobacteria and lymphoma. With refinement and improved availability of test methodologies in the future, clinical assessment of CD4+ T cell counts, the CD4+/CD8+ ratio, and plasma viral loads may facilitate interpretation of the relationship between disease manifestations and infection and provide pr ognostic information, as in human patients infected with HIV.

Indications for testing for FIV

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• Sick cats, even if tested negative in the past • All newly acquired cats or kittens (2 tests, at least 60 days apart) • After exposure to a retrovirus-infected cat or a cat with unknown status, and

especially after a bite wound (2 tests, at least 60 days apart) • Cats that live in a household with other retrovirus - • Infected cats (annual retesting unless isolated) • Before initial vaccination with FeLV or FIV vaccines • Before use as a blood donor (in conjunction with real- time PCR) • On entry to a shelter or before adoption (2 tests, at least 60 days apart); if financial

resources are not available for this, cats should be held singly and postadoption testing (2 tests, at least 60 days apart) recommended before mingling with other cats occurs. The status of the other cats in the household should be known before new cats are introduced.

• For group-housed cats, before introduction (2 tests, at least 60 days apart if possible) and on an annual basis

• Testing is considered optional for feral cat trap-neuter-return programs

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Laboratory Abnormalities Complete blood count Common abnormalities on the CBC in cats infected with FIV inclu de mild anemia, lymphopenia, and neutropenia. Occasionally severe anemia, thrombocytopenia, thrombocytosis, mono- cytopenia, or leukocytosis occur. In one large European study, neu trophil counts of FIV-infected cats were lower than those of control cats, and lymphocyte counts were higher than those of control cats. Leukopenia and neutropenia were more likely to be present in FIV-infected cats.

Serum biochemistry The most common and significant abnormality on the chemistry panel in cats infected with FIV is hyperproteinemia, which results from increased y-globulin concentrations and is a direct result of FIV infection (rather than the result of opportunistic infection). Total protein concentrations that

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ranged from 4.5 to 11 g/dL were reported in one study. Other findings are variable and relate to the presence of concurrent disease, neoplasia or opportunistic infections.

Urinalysis A proteinuria may be present if a glomerulonephritis is present.

Bone marrow cytology Bone marrow cytologic evaluation in FIV-infected cats with cytopenias and nonregenerative anemias may show mild dypla sia (usually not as severe as in FeLV infections); erythroid hypoplasia; and/or myeloid hyperplasia despite peripheral leukopenia, sometimes with a left shift. The latter suggests ineffective hematopoiesis or maturation arrest.

Microbiologic Tests Serology The initial assay of choice for diagnosis of, and screening for, FIV infection is an ELISA assay that detects antibody to FIV. Provided there has not been a history of vaccination for FIV and the tested cat is less than 6 months of age, positive antibody test results equate with infection, because the virus establishes a lifelong, persistent infection. Point-of -care, lateral-flow ELISA assays and diagnostic laboratory -based ELISA assays are in widespread use and have rapid turnaround times and high sensitivities and specificities. These assays usually detect antibodies t o the FIV p24 core protein, and sometimes to the gp40 transmembrane protein. False positive test results occur rarely as a result of operator error or nonspecific reactivity against tissue culture components after vaccination. When these assays are used to screen healthy cats for infection, confirmation of positive results is recommended because of the low prevalence of infection in this population of cats and the higher possibility that false-positive test results may occur. Confirmation can be done using a test from a different company. Positive ELISA assay results in the absence of FIV infection can occur in cats that have been vaccinated for FIV, or kittens less than 6 months of age that possess maternal antibody (because of infection or vaccination of the queen). No currently available serologic test, including Western immunoblotting, distinguishes between natural infection and vaccination or the presence of maternal antibody. Kittens that test positive should be retested after 6 months of age. Nevertheless, kittens less than 6 months of age should still be tested, because the vast majority of negative kittens will be declared free of infection. Molecular testing could be considered to confirm infection in kittens that test positive at less than 6 months of age (see later discussion). Cats with a history of FIV vaccination may remain antibody- positive for more than 4 years. Because infection can occur in the face of vaccination, positive test results in a vaccinated cat may represent infection and/or historical vaccination. Currently, molecular testing with PCR assays is required to identify infection in these cats, but some infected cats test PCR-negative. An ELISA assay has been developed that can distinguish naturally infected

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from vaccinated cats, but this assay is not commercially available. The assay was used to test blood samples from 73 uninfected, unvaccinated cats; 89 uninfected, FIV-vaccinated cats; and 102 FIV-infected cats, including 3 cats that had been vaccinated. The assay had a sensitivity of 97% and a specificity of 100% for detection of FIV infection in these cats. False-negative ELISA assay results occur early in the course of illness, because cats may take up to 60 days to develop an antibody response. Rarely, antibody production is delayed for 6 months or longer. Thus when recent exposure is possible, testing should be repeated a minimum of 2 months later. False negative test results also occur in cats in the terminal phase of disease, as a result of impaired antibody production, or in kittens with rapidly progressive infections. These cats often have high plasma viral loads. Thus, if advanced FIV infection is suspected, negative test results should be followed by virus detection using PCR. When serology is used as a screening test, negative results are considered to be highly reliable because of the high sensitivity of the test and the low prevalence of infection in most populations of healthy cats.

Molecular diagnosis by PCR A variety of PCR assays have been developed for diagnosis of FIV infection. Assays may detect viral RNA (reverse transcrip- tase [RT]-PCR), proviral DNA, or both RNA and proviral DNA in peripheral blood. Because the FIV vaccine is inactivated and does not integrate or replicate in the host genome, PCR assays should not detect vaccine virus in cats that have been vaccinated for FIV. Compared with serology, PCR can be insensitive (sensitivity < 0%), because viral loads in healthy cats are often extremely low , and some strains may not be detected because of variablility in the sequence of the viral genome among FIV isolates. Sensitivity is likely to be higher in cats in the actute and terminal phases of the disease when the viral loads are higher. False positives have the potential to occur as a result of lab contamination. Given the limitations, PCR should not be used in dioagnosis, and the results should not be used to decide to vaccinate or not. Sero-negativity in the presence of PCR positivity indicates terminal disease or a false result.

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SAVA KZN Branch Meeting San Lameer

21-22 May 2016

Petrie VogelTel: 012 346 0687Fax: 012 346 [email protected]

Avoiding Common Pitfalls Dr Phil Rees

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Improving Survival in Diaphragmatic Hernia Cases

Dr Sara Boyd, BVSC MMedVet (surg.)

Johannesburg Specialist Veterinary Centre, 63 Kayburne Avenue, Randpark Ridge, South Africa

[email protected]

Introduction Diaphragmatic hernia (DH) is the protrusion of abdominal organs through an abnormal opening in the diaphragm. The vast majority of these hernias are caused by blunt abdominal trauma and result in impaired lung expansion and respiratory difficulty1-7. The combination of trauma, a compromised patient and the cardiovascular effects associated with diaphragmatic hernia, can make this condition life threatening and daunting to treat. A rapid assessment of the patient’s vital signs, administration of intravenous fluids and oxygen and rapid diagnosis of the condition all improve rates of survival7. Anatomy The diaphragm is a musculo-tendinous structure that divides the abdomen from thoracic cavity2. It consists of the following muscular components the: Pars Sternalis, Pars Costalis and two sections of Pars Lumbarlis. Various hiatal openings occur in the tendinous portion of the diaphragm. These facilitate the passing through of the oesophagus, aorta and caudal vena cava. The nerve innovation of the diaphragm is supplied by the left and right phrenic nerves. Blood supply comes from Phrenicoabdominal arteries that branch off the aorta1,2. Types of Diaphragmatic Hernia Hernias in small animals may be congenital or traumatic. Diaphragmatic hernias occur at the weakest points in the diaphragm which is usually the muscular portions. Size and location of the tear depends on the force of the trauma and the position of the abdominal organs at the time of impact1. Traumatic hernias are much more common and account for 77-85%. In cats the majority of diaphragmatic hernias are circumferential in nature, whereas in dogs, if is an even split between radial orientation and circumferential tears1,2,7. Congenital hernias are either pleuroperitoneal or peritoneopericardial in nature and account for less than 10% of all hernias. Peritoneopericardial hernias (PPH) are by far the most common congenital hernias and occur when abdominal contents move through from the abdomen and into the pericardial sac. The muscosal lining to these cavities is uninterrupted. Predisposed breeds include: Weimaraners and Cocker Spaniels. Congenital PPH are often associated with other cardiovascular defects like ventricular septal defects, aortic stenosis, portocaval shunts and abdominal wall defects. Onset of clinical signs may be delayed until dog is 1 to 3 years old, due to large defects and lack of entrapment of organs. When early diagnosis does occur, surgical repair can be performed from as young as 6 to 8 weeks of age. A very good prognosis of around 80-90% can be achieved7. If the hernias are small, viscera may become trapped causing incarceration and necrosis. If small portions of mesentery or liver are trapped, they can produce vast quantities of fluid resulting in hydrothorax and severe respiratory compromise1,3. The liver is the most commonly herniated organs. The next most common is the stomach, which in itself can be dangerous due to rapid gas expansion and mass effect.

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Emergency Care The clinical signs depend on the extent of the defects, the amount of lung compression and the degree of pleural fluid accumulation. Most animals present in shock acutely after the trauma, however 15-25% are only diagnosed weeks after the injury. Signs include dyspnoea, cyanosis, exercise intolerance, chronic vomiting and a poor appetite. Remembering that cardiovascular dysfunction and the related hypotension are the most likely factors to cause death, it is important that these are corrected immediately. On presentation, an emergency score needs to be assessed. This includes temperature, heart rate, blood pressure and level of patient’s mentation. It has been shown that if we identify these patients early and treat rapidly, we greatly decrease the mortality rates. Diagnostic techniques Survey radiography of the thoracic cavity is by far the most easily available and useful diagnostic technique. Signs that could indicate the presence of a diaphragmatic hernia include: gas shadows of small intestines in the chest cavity, spleen, liver or stomach densities in the chest, loss of the diaphragmatic line, lung lobe collapse, loss of the cardiac silhouette and lack of usual abdominal organs (stomach or liver) on radiographs of the abdominal cavity. Studies showed that radiographs yielded evidence of DH in approximately 66% of affected animals1,3,5,6. Ultrasonography can also be useful in cases where there is extensive pleural effusion and radiographs do not provide sufficient contrast. It is non invasive and carries a 93% rate of accuracy. It may also aid in the collection of pleural fluid, which can be used for further diagnostic clarity. Signs that are observed for in ultrasonography include: irregular cranial hepatic borders, abdominal organs situated lateral or cranial to the heart. The entrapped gastric bubble may obscure definition and the actual tear is usually difficult to visualise3,6. In cases where the diagnosis is still unclear, positive contrast gastrography or peritoneography can be attempted. Water soluble, iodinated contrast medium is injected into the peritoneal cavity at 2ml/kg dose and should appear in the thoracic cavity within 5-20 minutes if a DH is present. False negatives occur when omental adhesions have already closed off access to the thorax6. Timing to surgery Timing of surgical correction of diaphragmatic hernias has been a controversial subject for many years. Historically research stated that surgery for DH carried a 33% mortality rate when attempted within the first 24 hours. Since then, many follow up studies have shown that provided adequate cardiovascular support is provided; surgery of DH within the first 24 hours carries an 89% prognosis for survival1,2. Emergency surgical correction is mandatory when there is gastric or liver lobe entrapment and when there is hypoventilation due to the mass effect hindering lung expansion. Anaesthesia Repair of DH should occur as soon as possible after diagnosis and stabilisation of the patient. Some tips that may significantly increase survival time include: preoxygenating the patient prior to induction, rapid intravenous induction to facilitate intubation and positive pressure ventilation to combat the concurrent lung damage and collapse7. Positioning of the patient is extremely important. Where possible, patients should be clipped prior to GA induction and should always be maintained with their heads at a higher level than their abdomens, so that gravity can help keep abdominal organs off the heart and lungs. Dorsal recumbency is particularly detrimental to the respiration in these patients and should be kept to a minimum. On the whole, the surgeons in charge should be aiming for a short, balanced anaesthesia where cardiovascular function is carefully monitored and hypothermia is avoided.

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Respiratory depressant drugs should be avoided and a prophylactic, broad spectrum antibiotic is usually administered pre-surgery and 4 and 8 hours post operative. Pain control with opiods is more beneficial than detrimental, as pain causes anxiety and respiratory depression and may further compromise these animals1. Percutaneous opiods via a skin patch (Duragesic patches) are very useful and will provide adequate pain relief for 12-72 hours post surgery, without suppressing respiration. Due to the open chest nature of this type of surgery, positive pressure ventilation is necessary. This can be provided via a ventilator or via manual compressions of the reservoir bag. Monitoring PO2

levels, body temperature and blood pressures can further influence rate of survival. Surgery The surgical approach to the repair of diaphragmatic hernias is via a ventral midline incision. The incision should run from the lateral xiphoid region to a distance past the umbilicus (depending on the size of the patient. This allows for rapid identification of the tear and access to the tear for repair. In some cases a paracostal or “T-shaped” incision in the abdominal wall is necessary to allow better access. Stay sutures placed in the diaphragm may further aid in reducing the hernia and bringing the tear more into the operating field. Diaphragmatic ruptures are usually sutured in a continuous pattern starting at the furthest, least accessible portion of the tear and working towards the surgeon. Major blood vessels like the aorta and Caudal Vena Cava need to be identified and avoided. A size 2/0 or 0 monofilament non absorbable suture material with a smooth swagged on needle is historically the choice for this repair. Chest drains should always be inserted at the time of surgery to allow for evacuation of air from the thoracic cavity post surgery. These chest drains may exit through the hernia repair and the abdominal incision, as they are removed shortly after surgery1,2,4. Difficulties encountered during surgery include entrapment of liver lobes that may be friable and have a tendency to bleed profusely when reduced. It is always advisable to rather increase the size of the original DH, if reduction of these parenchymous organs is difficult. Blunt dissection of associated fibrous adhesions may also be necessary, especially in chronic cases. These adhesions can also cause profuse bleeding and need to be identified and corrected4. Post decompression of the chest cavity, lungs should be allowed to reexpand slowly and never be forcibly dilated. Forcing air into the lungs greatly increases the chance of reperfusion injury and even rupture to the lungs. Chronic compression of lungs, may take a few weeks to get back to normal1,2,4. Conclusion Although DH can be a challenging presentation, they are also relative easy surgeries and can be extremely rewarding cases when handled efficiently. Acute cases have a lower mortality rate than chronic ones; however the prognosis is excellent in both groups with early surgery and careful monitoring through the post operative period. References

1. Fossum TW: Diaphragmatic Hernia: The wait is over: Diagnosing, Stabilization and Surgery. International Veterinary Emergency and Critical Care Symposium 2007.

2. Worth AJ, MAchon RG: Traumnatic Diaphragmatic Herniation: Pathophysiology and Managemnet. Compend Contin Educ Pract Vet 2005 Vol 27 (3) PG 178-191.

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3. Hyun C: Radiographic Diagnosis of Diaphragmatic Hernia: Review of 60 Cases in Dogs and

Cats. J Vet Sci 2004 Vol5 (2) Pg 157-162.

4. MInihan AC, Berg J, Evans KL: Chronic Diaphragmatic Hernia in 34 Dogs and 16 Cats. J Am Anim Hosp Assoc 2004 Vol 40 (1) pg 51-63.

5. MacPhail C: Diaphragmatic Hernia. Blackwells Five Minute Veterinary Consult, Canine and Feline. Wiley-Blackwell 2011 pg 371

6. Williams J, Leveille R, Myer CW: Imaging Modalities Used to Confirm Diaphragmatic Hernia in Small Animals: Compend Contin Educ Pract Vet 1998 Vol 20 (11) pg 1199-1209

7. Gibson TWG, Brisson BA, Sears W: Perioperative Survival Rates After Surgery for Diaphragmatic Hernia in Dogs and Cats: 92 Cases (1990-2002) J Am Vet Med Assoc 2005 Vol227 (1) pg 105-109

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Antibiotic therapy in small animal dermatology Adapted from: Guidelines for the diagnosis and antimicrobial therapy of canine superficial bacterial folliculitis (Antimicrobial Guidelines Working Group of the International Society for Companion Animal Infectious Diseases). Hillier, A. et al. in Vet Dermatol 2014; 25: 163–e43 In dogs, superficial bacterial folliculitis (SBF) is the commonest form of canine pyoderma, which is in turn, the principal reason for antimicrobial use in small animal practice. As we face the problem of increasing antimicrobial resistance in both human and veterinary medicine, there is a pressing need for prudent and more focused use of antimicrobial drugs (AMDs). In the human field, adoption of guidelines for antimicrobial use at the hospital level has been shown to improve prescribing practices significantly, both alone and as part of broader antimicrobial stewardship programs. Similar benefits can be expected in the veterinary field. The diagnosis of canine pyoderma The predominant pathogen that causes pyoderma is Staphylococcus pseudintermedius (previously known and referred to as Staphylococcus intermedius). Although dogs may carry or be colonized and infected by Staphylococcus aureus and by the coagulase-variable species (Staphylococcus schleiferi), these are far less frequent pathogens in pyoderma. Coagulase-negative staphylococci (CoNS; such as Staphylococcus epidermidis and Staphylococcus xylosus) may rarely be cultured from lesions of pyoderma, usually in association with S. pseudintermedius. Clinical signs In practice, the diagnosis of most cases of pyoderma is based upon clinical signs and the presence of characteristic lesions; there is no evidence that these differ amongst infections caused by the different staphylococci. Common lesions of pyoderma are erythematous papules and pustules, typically associated with hair follicles. However, follicular involvement may be difficult to appreciate macroscopically. Crusts of variable thickness are common lesions but are sometimes absent. Variable alopecia, erythema and hypo- or hyperpigmentation are often present. Multifocal to coalescing patches of alopecia providing a ‘moth-eaten’ appearance may be the only visible lesions in some short-coated breeds. Epidermal collarettes and target lesions (annular areas of alopecia, scaling, erythema and hyperpigmentation may be the most obvious lesions in some cases. Almost all allergic skins will carry significant bacterial load (dermal barrier is compromised) that aggravates the underlying allergic inflammation and pruritus. Treating this may result in quite significant improvement in clinical score. Unmanaged (undiagnosed) underlying allergic skin disease is the most common reason for relapsing pyoderma in dogs.

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Cytology Demonstration of cocci from lesional skin by cytology is a powerful adjunctive diagnostic test and is strongly encouraged for proper diagnosis. Appropriate techniques need to be used for both specimen collection and examination to optimize the value of this diagnostic procedure. Cytology is mandatory in the following circumstances:

(i) typical lesions (pustules) are not present or scant and pyoderma is still suspected; (ii) typical lesions are present but there is a poor response to empirical antimicrobial

therapy; or (iii) a bacterial culture is to be performed. This is because positive cytology in the face of

a negative culture should prompt repeat culture rather than diagnosis of a sterile pustular disease.

Cytology is also essential for the diagnosis of co-infection with Malassezia pachydermatis (a frequent occurrence in dogs with pyoderma) or rod-shaped bacteria (a rare occurrence in dogs with pyoderma). The presence of coccoid bacteria in cytological specimens from typical lesions is highly supportive of bacterial infection; when associated with inflammatory cells and intracellular cocci from intact pustules, infection is confirmed. The absence or scarcity of bacteria and the absence of inflammatory cells or intracellular cocci do not rule out a bacterial infection. Inflammatory cells and phagocytosis may be absent in dogs with underlying immunosuppressive diseases or those being treated with immunosuppressive agents, such as glucocorticoids. Tests to rule out differential diagnoses Superficial bacterial folliculitis should be distinguished from other inflammatory follicular diseases and is differentiated from dermatophytosis by dermatophyte culture (or Wood’s lamp evaluation or direct examination of hairs for spores) and from demodicosis by deep skin scrapings. Such testing is recommended, and is essential, when history and clinical findings are atypical of pyoderma or the disease is refractory to AMD treatment. Sterile pustular diseases (such as pemphigus foliaceus and sterile neutrophilic or eosinophilic pustulosis) are uncommon to rare and are differentiated on the basis of cytology (absence of bacteria, presence of acantholytic cells), culture (no bacterial growth from sampled pustules), histopathology and lack of response to AMD therapy. Culture and susceptibility testing Bacterial culture of pyoderma is never contraindicated. There are primarily five situations which may indicate the likelihood of AMD resistance and mandate bacterial culture of apparent pyoderma, as follows:

(i) less than 50% reduction in extent of lesions within 2 weeks of appropriate systemic antimicrobial therapy (when underlying allergic skin disease is not a consideration); (ii) emergence of new lesions (papules, pustules, collarettes) 2 weeks or more after the initiation of appropriate AMD therapy;

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(iii) presence of residual pyoderma lesions after 6 weeks of appropriate systemic antimicrobial therapy together with the presence of cocci on cytology (while a typical course of therapy may be 21–28 days, several studies indicate that therapy for up to 6 weeks may be necessary to resolve the infection in some cases); (iv) intracellular rod-shaped bacteria are detected on cytology; and

(iv) there is a prior history of multidrug-resistant infection in the dog or in a pet from the same household as the affected dog.

As AMD use has been reported as a risk factor for infection with methicillin-resistant strains of S. pseudintermedius (MRSP) and S. aureus (MRSA), careful consideration for bacterial culture should be given to dogs with a history of recurrent infections or repetitive AMD use. As colonization with MRSP may persist after treatment of MRSP infections and MRSP may be isolated from dogs in contact with MRSP-infected pets, dogs with superficial bacterial folliculitis that have previously had MRSP infections or are from households with other pets that have had MRSP infections should have a bacterial culture performed prior to selection of treatment for their infection. In cases where initial treatment of pyoderma was limited to topical AMDs alone and the infections failed to resolve, it is acceptable either to perform bacterial culture and susceptibility testing or to institute empirical systemic AMDs. Clinicians commonly rely on pet owners to report on the progress of treatment of pyoderma. Thus, education of owners on the identification of the specific lesions and what changes to expect is critical; distinction must often be made between lesions of pyoderma (including papules, pustules and crusts) and signs of the primary underlying dermatopathy (such as alopecia, scaling, excoriation, hyperpigmentation and lichenification). As systemic AMDs are suggested to be dispensed for a minimum of 3 weeks, it is important that veterinarians educate owners not to continue AMD therapy in the absence of improvement of pyoderma lesions during this time, or with the emergence of new lesions after 2 weeks of therapy, without veterinary advice. Pustules are the preferred lesion for specimen collection, and a thorough search for pustules should be made. Clipping hair to facilitate examination of the skin surface and the use of a hand-held magnifying lens can be helpful in detecting pustules. In the absence of pustules, specimens may be obtained from beneath crusts (look for pus present under the crust), epidermal collarettes or papules. Specimen collection methods are summarized in Table 1. Immediate transport of the specimens to the laboratory is recommended, and transport medium should always be used (clinicians should consult with their laboratory if they are uncertain of how to transport their specimens). If delay in submission of specimens is unavoidable, advice on storage should be obtained from the relevant clinical microbiology laboratory. To date, there are no published reports demonstrating that current use of AMDs has a significant effect on isolation of causative bacteria from dogs with persistent pyoderma; thus, it

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is acceptable to collect samples for bacterial culture and susceptibility testing from pyoderma lesions whenever indicated, regardless of the current use of topical or systemic AMDs.

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Table 1. Sampling techniques for lesions of superficial bacterial folliculitis for bacterial culture and susceptibility testing

Lesion Sampling procedure Pustule No surface disinfection. Clip hair with sterile scissors (avoid clippers). Lance pustule with sterile

narrow-gauge needle. If purulent exudate is visible on the needle, apply to a sterile swab; if not, gently touch exudate expelled from pustule with sterile swab and place in transport medium or sterile container. Sometimes lancing of very small pustules results in haemopurulent exudate, which is still suitable for sampling

Crust No surface disinfection. Use sterile forceps or a sterile needle to lift the edge of a crust. The presence of exudate under a crust indicates an ideal site for culture. Touch sterile swab to exposed skin surface and place in transport medium or sterile container

Epidermal collarette

No surface disinfection. Clip hair with sterile scissors (avoid clippers). Roll sterile swab across border of collarette two or three times and place in transport medium or sterile container

Papule* Sampling by biopsy is probably more reliable. Provide local anaesthesia by subcutaneous injection of 2% lidocaine. Clip hair with sterile scissors or clippers. Clean skin surface by a single wipe with 70% alcohol† (no additional surgical preparation). Allow alcohol to dry. Using a sterile 3 or 4 mm punch and sterile surgical instruments, collect tissue sample and place in sterile container or transport medium. Suture biopsy site Alternatively, papules may be prepared and disinfected† as above, then sampled by insertion of a sterile needle and culture of emerging or expressed blood or exudate

*There is no research to show which method is more appropriate. †This method of disinfection is suggested to kill any surface bacteria. However, there is no research to indicate the value or necessity for any disinfection of the skin surface prior to sampling of papules.

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The following AMDs should be tested with all staphylococcal isolates: erythromycin, clindamycin, tetracycline (for testing susceptibility to doxycycline), trimethoprim– sulfamethoxazole, gentamicin, cephalothin (or cefazolin, representing first generation cephalosporins), cefpodoxime (representing third generation cephalosporins), amoxicillin– clavulanate, oxacillin (meticillin) and enrofloxacin (for testing susceptibility to fluoroquinolones). Inclusion of other fluoroquinolones may be considered if enrofloxacin is not the fluoroquinolone drug of choice. Additional AMDs that may be important for treatment of infections with meticillin-resistant staphylococci (MRS) include amikacin, chloramphenicol, minocycline and rifampicin (rifampin).

Guidelines for the interpretation of culture and sensitivity results are provided in Table 2.

Table 2. Guidelines for the interpretation of culture and sensitivity results

1 Note staphylococcal species isolated

Staphylococcus aureus is a human pathogen and therefore presents a higher public health risk Staphylococcus pseudintermedius is the predominant pathogen in bacterial infections of canine skin. It is a rare cause of human infection but presents enhanced risk if meticillin resistant Coagulase-negative staphylococci present a much lower level of risk but are often meticillin resistant. They are more likely to be involved in animals with reduced immunity and where implants are used. Low numbers of CoNS should be regarded as probable skin contaminants in patients that are not immunosuppressed, especially when isolated in mixed cultures.

2 Is the isolate reported as meticillin resistant?

Oxacillin is equivalent to meticillin and used as a marker of meticillinresistance. Oxacillin-resistant staphylococci are reported as ‘meticillin-resistant’ Meticillin (oxacillin)-resistant staphylococci are by convention resistant to all beta-lactam AMDs (cephalosporins, penicillins, carbapenems and monobactams), regardless of occasional apparent in vitro susceptibility. Clinical microbiology laboratories must report these isolates as resistant to all beta-lactam AMDs Meticillin-resistant staphylococci are commonly resistant to multiple antimicrobials in addition to the beta-lactam AMDs, but this is not always the case

3 Clinical disease status of patient and history of AMD use

Susceptibility results should always be interpreted in the context of the clinical disease and current and prior history of antimicrobial use in the patient, bearing in mind that susceptibility in vitro does not always parallel clinical response in infected animals

Recommendations for the treatment of canine pyoderma Veterinarians must consider the nature of the disease in each patient to determine the best mode of therapy. Traditional reliance on systemic AMDs and the expectation that empirical choices will always work are now being challenged by the growing frequency of MRS that are resistant to multiple classes of AMDs in addition to the beta-lactams. The prevalence of MRS will vary in different localities, and it is important for veterinary practitioners to become

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familiar with typical local and regional resistance patterns so that they may be prepared to make appropriate selections of modes of treatment and AMDs. Factors that impact therapy, in addition to antimicrobial resistance, include the severity and extent of lesions, patient factors (such as hair coat, temperament and environment), concurrent disease and the owner’s ability to perform topical or systemic therapy, all of which may affect the efficacy of the chosen therapy. Owners’ compliance with instructions and completion of treatments is critical to the resolution of infection and prevention of recurrence. Clinicians should maintain contact with owners and support them as far as possible to promote effective compliance. When recurrence of pyoderma occurs, veterinarians should present owners with a diagnostic plan for evaluation of underlying primary disease (allergic dermatitis, endocrinopathy, etc.) and make it clear that this is the best means to control recurrence of pyoderma, reduce AMD use and reduce the likelihood of emergence of drug-resistant infections. Topical antimicrobial therapy Topical therapy of SBF is probably underused because of the perception that clients will find it more difficult to apply and that compliance may be poor. However, there are significant potential advantages for early and frequent use of the topical approach in this disease. These advantages include more rapid lesion resolution and a decrease in the duration of antimicrobial administration when combined with systemic AMD therapy, removal of organisms and debris from the skin surface, minimal adverse effects and greatly reduced exposure to AMDs of bystander organisms in other organ systems (reducing risk of inadvertent emergence of resistant strains). In addition, resistance to the high concentrations of antiseptics and AMDs used in topical products is very uncommon, and these agents are typically bactericidal to MRS. The emergence of highly multiresistant MRS with few or no options for systemic AMD therapy has provided a new stimulus for the topical approach, which is emerging as an important treatment for multidrug-resistant bacterial infections of the skin. The benefits and importance of topical antimicrobial therapy and topical therapies that help to restore normal skin structure and function (promoting recovery and enhancing resistance to infection) are likely to emerge as significant options as systemic therapy becomes more limited. In general, topical therapy is helpful in all patients with pyoderma. Topical therapy alone (without co-administration of systemic AMDs) is encouraged as a desirable and recommended approach to the treatment of pyoderma unless precluded by owner and/or patient factors. This is particularly true in the following circumstances:

(i) localized lesions of pyoderma; (ii) early stages of generalized pyoderma when lesions are mild; and (iii) to help prevent recurrence of pyoderma while diagnostic procedures for primary

underlying skin disease are pursued.

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Topical approaches for SBF are summarized in Table 3, While it is difficult to estimate the concentrations of topical antimicrobial agents achieved at sites of application and difficult to assess the validity of in vitro antimicrobial susceptibility tests for topical agents, it is likely that high concentrations of these agents are achieved at sites of application. Table 3. Summary of topical antimicrobial treatment options for superficial bacterial folliculitis in the dog

Application Formulations Agents and modes of useExtensive or generalized disease

Shampoos, lotions, sprays, rinses and conditioners

Antiseptics, including chlorhexidine, or benzoyl peroxide are preferred, although ethyl lactate, povidone iodine and triclosan may also provide benefit. Commonly used two or three times weekly until 7 days after lesions resolve and then weekly for prophylaxis.* Can also be used for more localized disease. For shampoos that are rinsed from the skin, contact time of 10 min prior to rinsing is important.

Focal and localized infections

Gels, creams, ointments, lotions and wipes

Antiseptics, including a variety of hydroxyl acids (e.g. acetic, lactic and malic acids), benzoyl peroxide and silver sulfadiazine. Antimicrobial drugs, including novobiocin, pristinamycin, bacitracin, fusidic acid and mupirocin. Mupirocin and fusidic acid are used in human medicine for meticillin-resistant Staphylococcus aureus treatment and decolonization; resistance is increasingly reported. Reports indicate that resistance to topical therapy with these agents in meticillin-resistant staphylococci causing canine superficial bacterial folliculitis is very rare; however, it is recommended that they be reserved for targeted application in dogs with infections where culture and susceptibility indicate no other suitable antimicrobial drugs and where topical antiseptics have failed to resolve the infection

*Extended treatment duration is based on clinical experience; further research is required to confirm the need for this.

A recent systematic review found ample evidence for the efficacy of chlorhexidine for treatment of pyoderma, but to a lesser degree for the efficacy of benzoyl peroxide, fusidic acid and mupirocin. Further studies are needed to evaluate optimal protocols (such as frequency of application, duration of treatment and optimal contact time of antimicrobial agents) for topical therapy in the treatment and resolution of pyoderma. In the absence of these studies, it is recommended that topical antimicrobial therapy be continued until 7 days beyond clinical resolution of all lesions associated with the infection, that contact time should be at least 10 min and that the hair coat be kept short to assist optimal contact of antimicrobial agents with the skin surface. Veterinarians are strongly encouraged to provide guidance to owners on topical therapy by thorough verbal communication, audiovisual demonstrations in the clinic or at home, handouts, in-hospital bathing services and the like.

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Systemic antimicrobial therapy Selection of systemic AMDs is based on availability, safety, cost, local prevalence of resistant staphylococci and patient-specific factors (concurrent disease or drug administration, previous drug reactions, etc.). A recent systematic review found the evidence for efficacy of systemic AMDs for treatment of superficial pyoderma to be good for cefovecin, fair for amoxicillin–clavulanate, clindamycin, cefadroxil, trimethoprim–sulphamethoxazole and sulfadimethoxine–ormetoprim and insufficient for cefalexin, cefpodoxime, ibafloxacin, marbofloxacin and lincomycin. Despite the value of such reviews, the relative dearth of published studies, lack of standardization of methods for diagnosis and assessment of treatment outcome, as well as the absence of studies with many commonly used AMDs, prevent generation of comprehensive guidelines based solely on their findings. Choices of suitable AMDs that may be selected for empirical therapy of pyoderma when risk factors for likelihood of AMD resistance are not present (see indications for bacterial culture above) are grouped as first tier drugs (Table 4). Those AMDs that may be chosen when first tier drugs and topical agents are not appropriate and when culture and susceptibility results indicate susceptibility are grouped as second tier drugs (Table 4). Third tier drugs are also listed, but their use is strongly discouraged and it is recommended that cases be referred for specialist consultation if such AMDs are being considered. Suggested doses for antimicrobial drugs for systemic treatment of superficial bacterial folliculitis in the dog are given in Table 5. Table 4. Summary of systemic antimicrobial treatment options for pyoderma in the dog

Category When used Suggested AMDs and commentsFirst tier Primary choice empirical

therapy of known or suspected SBF

Clindamycin or lincomycinFirst generation cephalosporins (e.g. cefalexin, cefadroxil), Amoxicillin–clavulanate Trimethoprim- and ormetoprim-potentiated sulphonamides

First or second tier

Third generation cephalosporins (cefovecin, cefpodoxime).

Second tier When empirical selection of first tier systemic AMD and topical therapy are not appropriate and when cultures indicate susceptibility

Doxycycline or minocycline Chloramphenicol Fluoroquinolones (such as enrofloxacin, marbofloxacin, orbifloxacin, pradofloxacin and ciprofloxacin) (should only be used when other feasible options are not available) Rifampicin. Commonly used in combination with another drug to which the causative organism is susceptible Aminoglycosides, including gentamicin and amikacin. See Table 5 for comments on nephrotoxicity and ototoxicity First tier AMD (clindamycin, lincomycin and potentiated sulphonamides) may also be considered when cultures indicate susceptibility

Third tier When first and second tier are not appropriate and cultures indicate susceptibility

Linezolid, teicoplanin, vancomycin. Regardless of the fact that most (or all) MRSP are susceptible, the use of these three AMDs is strongly discouraged. These drugs can be considered ‘reserved for the treatment of serious MRSA infections in humans’.

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Table 5. Suggested doses for systemic antimicrobial drugs for treatment of superficial bacterial folliculitis in the dog

Drug Dose Comments Amikacin 15–30 mg/kg i.v., i.m. or s.c. once daily Useful for treatment of multidrug-

resistant organisms. Potentially nephrotoxic and ototoxic. Avoid in animals with renal insufficiency*

Amoxicillin–clavulanate Cefalexin, cefadroxil Cefovecin

12.5–25.0 mg/kg p.o. twice daily15–30 mg/kg p.o. twice daily 8 mg/kg single s.c. injection

Pharmacokinetic data are available to support the use in dogs with duration of 14 days. Repeat injection after 14 days in most cases if infection is not resolved and to meet the criterion for treatment to 7 days beyond resolution

Cefpodoxime proxetil Chloramphenicol

5–10 mg/kg o.o. once daily40–50 mg/kg p.o. three times a day

Reserved for multidrug-resistant infections with few other options. Myelosuppression can occur, particularly with long-term therapy. Vomiting is frequently encountered. Avoid contact by humans because of rare idiosyncratic aplastic anaemia. Wearing of gloves by owners handling the drug is essential

Ciprofloxacin 25 mg/kg p.o. once daily Sometimes used because of lower cost than enrofloxacin. Lower and more variable oral bioavailability than enrofloxacin, marbofloxacin and orbifloxacin. Difficult to justify over approved fluoroquinolones. Dosing recommendations are empirical

Clindamycin 5.5–10 mg/kg p.o. twice daily Doxycycline Enrofloxacin Lincomycin Gentamicin

5 mg/kg p.o. twice daily or 10 mg/kg once daily5–20 mg/kg p.o. once daily 15–25 mg/kg p.o. twice daily 9–14 mg/kg i.v., i.m. or s.c. once daily

Potentially nephrotoxic. Avoid in animals with renal insufficiency*

Marbofloxacin Minocycline

2.75–5.5 mg/kg p.o. once daily10 mg/kg p.o. twice daily Pharmacokinetics and dose in dogs have

not been evaluated;

Orbifloxacin Ormetoprim–sulfadimethoxine

7.5 mg/kg p.o. once daily55 mg/kg on first day, then 27.5 mg/kg p.o. once daily

Concerns regarding idiosyncratic and immune-mediated adverse effects in some patients, especially with prolonged therapy. If prolonged (>7 day) therapy is anticipated, baseline Schirmer’s tear testing is recommended, with periodic re-evaluation and owner monitoring for

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ocular discharge. Avoid in dogs that maybe sensitive to potential adverse effects, such as keratoconjunctivitis sicca, hepatopathy, hypersensitivityand skin eruptions

Pradofloxacin Rifampicin

3.0 mg/kg p.o. once daily5–10 mg/kg p.o. twice daily May cause red/orange urine, tears and

saliva. Hepatotoxic. Associated with rapid development of resistance

Trimethoprim–sulfadiazine or sulfamethoxazole

15–30 mg/kg p.o. twice daily See comments for ormetoprim–sulfadimethoxine above

In principle, it would be ideal if veterinarians had available a selection of AMDs for empirical therapy that were narrow spectrum, labelled for treatment of pyoderma in the dog and to which a majority of S. pseudintermedius were still susceptible. Unfortunately, this is rarely possible. Few of the commonly used AMDs are narrow spectrum, many AMDs that are registered and approved for use in the treatment of pyoderma may be associated with the emergence of multidrug resistant infections, and there is distinct geographical variability in susceptibility of S. pseudintermedius to many of the available AMDs. A few recent studies in dogs have identified antimicrobial drug use in general as a risk factor for the emergence of MRSP and, at present, it is reasonable to assume that any cephalosporin or amoxicillin–clavulanic acid could select for MRSP. One small report has associated misuse of unspecified fluoroquinolones, macrolides and third-generation cephalosporins with persistence of MRSP colonization in a breeding kennel. The use of fluoroquinolones and extended-spectrum cephalosporins in humans, and of fluoroquinolones in dogs, is a known risk factor for selection of MRSA. Use of these AMDs is also a risk factor for selection of extended-spectrum beta-lactamase (ESBL)-producing E. coli in both humans and animals, and guidelines in human medicine recommend prudent use of these broad-spectrum agents to prevent spread of multidrug-resistant bacteria. These factors, along with the increasingly high prevalence of MRSP and ESBL-producing Enterobacteriaceae in dogs, support the promotion of precautionary principles and the limitation of extended-spectrum cephalosporins and fluoroquinolones as second tier AMDs. In accordance with this, the package insert for cefovecin in Europe specifies that ‘A sample of the lesion should be obtained for culture and susceptibility testing prior to beginning antimicrobial therapy’, and the technical monograph states, in addition, ‘It is prudent to reserve third generation cephalosporins for the treatment of clinical conditions, which have responded poorly, or are expected to respond poorly, to other classes of antimicrobials or first generation cephalosporins’. With regard to the fluoroquinolones, enrofloxacin, marbofloxacin,orbifloxacin and pradofloxacin are approved for use in dogs in some countries and have been shown to be effective for the treatment of superficial pyoderma. However, the use of this group of AMDs is a known risk factor for the emergence of MRSA in humans, and guidelines also recommend limited use of these agents.

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When recurrence of pyoderma occurs, careful consideration of culture and susceptibility testing is encouraged because previous exposure to AMDs is a risk factor for resistance and may be especially important in patients with previous MRSP infections or from households with other pets that have previously been diagnosed with an MRSP infection. Veterinarians should present a plan for evaluation of underlying primary disease to owners of dogs with recurrent infections. If culture is not performed on recurrence of the infection, the same AMD should be used that successfully resolved the previous infection. Most studies evaluating the efficacy of AMDs indicate that pyoderma infections are resolved after 3 weeks or more of systemic AMD treatment; rapid improvement over the first 1–2 weeks is typically observed, but resolution of all lesions and prevention of rapid recurrence of disease requires 3–6 weeks of treatment. Although there is no significant difference in the likelihood of resolution of MSSP after 3–4 weeks of systemic AMD treatment compared with MRSP infections, it has been reported that MRSP infections took longer to treat compared with MSSP infections. In a minority of patients, resolution of lesions may be achieved with 2 weeks of systemic AMDs. However, the assessment of complete resolution cannot be left to pet owners, and all patients should ideally be re-evaluated to ensure resolution of the infection. In particular, if attending veterinarians dispense <3 weeks of AMDs, they should anticipate and be confident that the patient will be presented for re-evaluation to determine whether additional antimicrobial therapy is indicated or the infection has resolved on completion of this period. Furthermore, patients with a history of recurrent pyoderma must be re-evaluated at the conclusion of AMD treatment. In the absence of evidence to the contrary, continuation of treatment for at least 7 days beyond clinical resolution of lesions is recommended in all cases, because the inflammatory process and lesions will subside and become inapparent as the infection is eliminated. This extended duration of treatment is based on clinical experience. Further research is required to confirm the need for such additional therapy, whether a 7 day period is sufficient, and to determine methods that will confirm whether infection has been eliminated when clinical lesions have resolved. Concurrent glucocorticoid use during therapy of pyoderma is strongly discouraged because it may improve the clinical appearance of the lesions and result in premature discontinuation of AMD administration whilst also reducing the patient’s innate and adaptive immune response to infection. Prevention of superficial pyoderma The most effective measure to prevent recurrence is to identify and control the underlying primary disease. Protocols for the use of systemic AMDs to aid in the prevention of superficial pyoderma, or to delay recurrence, have been published and advocated in public prior to the widespread emergence of MRS and have included pulse therapy (intermittent administration of therapeutic doses of AMD) and continuous use of sub-therapeutic dosing. However, there is significant concern for the selection of resistance with these protocols. Accordingly, their use is discouraged. Every effort must be made to identify predisposing diseases (allergies and immunosuppressive disorders) and to make maximum use of topical therapies.

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Public health considerations Staphylococci can be transferred in both directions between animals and humans. Whilst the risk of infection with S. pseudintermedius and S. schleiferi is very low in healthy humans, infections by pathogenic staphylococci acquired from pets have been documented. Such infections are a much greater hazard in the case of MRS, particularly with MRSA. Precautions need to be taken to limit the possibility of transfer of staphylococci from infected animals to owners and veterinary staff in the clinic. Owners and veterinary staff need to be aware of this potential hazard and advised on measures to minimize the risk of transfer, particularly when susceptible individuals (elderly people, those with lesions or diseases rendering them more susceptible to infection and those receiving immunosuppressive therapy) are likely to come into contact with the affected animals. Infection control measures Hygiene should be maintained rigorously in the clinic when animals suspected of having staphylococcal infections are admitted. Staff should be trained to recognize risk factors for multiresistance and observe such protocols; compliance should be monitored and enforced. Materials likely to have been contaminated should be disinfected after such animals are seen, and effective hand cleansing with alcohol sanitizers must be carried out before and after touching the animal. Owners of animals with suspected staphylococcal infections should also be advised of the importance of hygiene.

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DAIGNOSIS AND MANAGEMENT OF OTITIS

Normal anatomy

Key points: • The external ear consists of the external acoustic meatus which collects and locates the origin of

sounds. • The middle ear consists of the tympanic membrane, the ossicles, the auditory tube, and the tympanic

cavity. It serves to transducer incoming airborne sound waves into waves in a liquid medium. • The inner ear consists of the cochlea, the vestibule, and the semicircular canals. These structures relate

the head to gravity, allowing the visual system to compensate for movement and to perceive both linear and rotational acceleration.

Tympanum This is a thin, semitransparent membrane with a rounded elliptical outline. Its mean size in the dog is 15 x 10 mm with an area of approximately 63 sq mm. The shorter dimension is nearly vertical. The long axis is directed ventral, medial and cranial. The feline tympanum is more circular and smaller. The majority of the external surface is rough, thin and glistening (the pars tensa) with the outline of the manubrium of the malleus being clearly visible. The manubrium exerts tension on the tympanum giving it a concave shape as seen from the outside (like the speaker cone of a loudspeaker). The pars flaccida is more opaque, pink, or white in colour. It is confined to the upper quadrant of the membrane.

Otoscopy

Abnormal appearance of the ear canal and tympanic membrane When evaluating the ear, one should note the condition of the ear canal (eg, erythema, stenosis, proliferation, ulceration); look for any foreign bodies or masses; note the presence, consistency, and color of any exudate; and evaluate the patency of the tympanic membrane. Inflammation as a result of any primary cause of otitis externa can result in oedema and erythema. The swelling caused by the oedema appears clinically as stenosis of the ear canal. There is gross enlargement and hypersecretion of sebaceous glands. A mixed infiltration of inflammatory cells migrates into the epidermis and dermis. In the early stages of otitis externa, intervention with anti-inflammatory drugs is important to stop the progression of the proliferative changes in the ear canal. Anti-inflammatory medications, such as oral and topical glucocorticoids, are indicated to reduce the inflammation and for pain control. If glucocorticoids are contraindicated in a patient, nonsteroidal anti-inflammatory medications may be used. With persistence of the ear disease, clinically, the ear canal continues to close down. Clinically, there are variable degrees of nodular proliferation. With time, the continued inflammation can lead to calcification and ossification of the auditory cartilages and fibrosis. A recent study documented that the changes that occur in the external ear canal in chronic otitis may be breed related, with moderate to severe hyperplasia and dilation of the apocrine glands occurring in more than 70% of Cocker Spaniels, whereas these changes were present in only 31% of the other breeds evaluated. Once these severe changes have occurred, it is usually not possible to resolve them even with anti-inflammatory drugs; in many cases, surgical intervention is necessary. Ulcerations of the ear canal are uncommon; when present, they are usually associated with a gram-negative bacterial infection, such as Pseudomonas aeruginosa. Inappropriate cleaning of the ear canal with cottontipped applicators, especially in an infected ear, can also result in ulcerations. If the ear is infected, oral and topical treatment is determined based on otic cytology and bacterial culture and antibiogram testing. In addition,

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glucocorticoids may be necessary to decrease the pain and inflammation associated with the ulcerations. Topical ear cleaners containing alcohol should be avoided until the ulcers begin to heal. An animal with a tumor in the ear canal may present with clinical signs similar to any patient with chronic otitis externa. Any tumor in the ear canal needs to be biopsied for identification. This may be accomplished using alligator forceps through the handheld otoscope, although it is best performed using the biopsy forceps through the working channel on the video otoscope under guided visualization. In some instances, there is a secondary infection, and the exudate may inhibit visualization of the mass. It may be necessary to clean the ear before the examination. Depending on the amount of exudate, the animal may need to be anesthetized to clean the ear completely. Once the ear canal is clean and a tumor is identified, a biopsy may be obtained. Tumors of the ear canal can arise from any of the structures of the ear canal, such as the squamous epithelium, glandular structures, and mesenchymal tissues. The tumors may be benign or malignant. The most common tumor found in the ear canal of the dog and cat is a ceruminous gland tumor. There is a greater tendency for malignancy and aggressive biologic behavior of these tumors in the cat than in the dog. Other tumors of the ear canal include squamous cell carcinoma, papillomas, sebaceous gland tumors, and mast cell tumors. There are nonneoplastic diseases that can mimic tumors of the ear canal, including hyperplasia of the ceruminous glands, inflammatory polyps, ceruminal gland cysts, and nodular hyperplasia of the sebaceous gland. Foreign bodies can cause an acute, painful, unilateral otitis externa. Rarely, they may cause a bilateral otitis externa. Some of the more common foreign bodies include plant awns, impacted wax, and inspissated otic preparations. The animal should be placed under general anesthesia to remove foreign bodies, especially if they are in close proximity to the tympanic membrane. With the aid of the video otoscope, grass awns may be removed using the grasping forceps through the working channel on the otoendoscope. Impacted wax and otic concretions should be dissolved with a ceruminolytic agent and then gently flushed out of the ear canal. In some instances, a curette is used to dislodge the obstruction. In most cases of chronic otitis externa, the tympanic membrane is difficult, if not impossible, to visualize otoscopically on the initial examination. Otic flushing is necessary to clean the ear so as to allow visualization of the tympanic membrane. If the ear canals are ulcerated or stenotic, however, administration of oral and topical glucocorticoids for 2 to 3 weeks is needed to decrease the inflammation and open the ear canals to allow for a proper ear flush. For a deep ear flush, the animal should be placed under general anesthesia and entubated. In this way, if a myringotomy is required or if the tympanic membrane is ruptured, the airway is protected to avoid aspiration of any fluid that may pass from the middle ear into the oral pharyngeal region via the Eustachian tube. In dogs with acute otitis externa, the incidence of otitis media is only 16%, whereas in dogs with chronic otitis externa, up to 88.9% may have concurrent otitis media. An intact tympanic membrane does not rule out otitis media and may be found in up to 72.5% of the ears of dogs with otitis media. In addition to allowing visualization of the tympanic membrane, the ear flush removes exudate that is irritating, masking a foreign body or tumor, serving as a nidus for infection, or capable of inactivating medications (eg, gentamicin, polymyxin B). If the tympanic membrane is ruptured, the animal has otitis media. Samples should be obtained from the middle ear for bacterial culture and antibiogram (C/B) and cytology. Using a handheld otoscope, a sterile otoscopic cone is inserted into the horizontal ear canal and a sterile swab is passed into the middle ear cavity. The first swab is used for C/A. A second swab is passed into the middle ear cavity for cytologic analysis. If the video otoscope is used, an open-ended 3.5-French tomcat catheter attached to a 10-mL syringe is placed through the working channel of the endoscopic otoscope. One milliliter of sterile saline is flushed into the middle ear cavity and aspirated back. The fluid is then cultured. A second sample is obtained for cytologic evaluation. The middle ear is flushed repeatedly with saline using an open-ended 3.5-French tomcat catheter attached to a 10-mL syringe passed through an otoscopic cone or through the working channel on the endoscopic otoscope to remove any ear cleanser from the middle ear completely so as to reduce the chance of ototoxicity. If the tympanic membrane is abnormal (eg, hemorrhagic, bulging, opaque, brown, grey), a myringotomy should be performed to obtain samples for bacterial C/A and cytology and to allow flushing and drainage of the middle ear cavity. It is important to make the myringotomy incision in the caudoventral portion of the pars tensa to avoid damaging the delicate structures in the middle ear. Using a handheld otoscope, an otoscopic cone is inserted into the horizontal ear canal and the tympanic membrane is visualized. Using a sterile swab, an incision is made blindly into the caudoventral quadrant of the pars tensa. The swab used for the myringotomy incision is submitted for bacterial C/A. A second swab is inserted into the original incision, and the sample obtained is

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used for cytologic analysis. If the video otoscope is used to perform the myringotomy, an open-ended 3.5-French tomcat catheter is placed through the working channel of the endoscopic otoscope, and under direct visualization, the tomcat catheter is used to make the incision into the caudoventral quadrant of the pars tensa. One milliliter of sterile saline is flushed into the middle ear cavity and aspirated back using a 10-mL syringe attached to the tomcat catheter. The fluid is then cultured. A second sample is obtained for cytologic evaluation. Once the samples have been obtained, the middle ear is flushed gently with saline through the tomcat catheter until the fluid aspirated back is clear. The normal tympanum has been shown experimentally to heal in 21 to 35 days. Therefore, if the ear is kept free from infection after the myringotomy procedure or if the membrane was already ruptured, the tympanic membrane should heal. Possible complications of ear flushing and myringotomy are Horner’s syndrome, facial nerve paralysis, vestibular disturbances, and deafness. Owners should understand these complications and sign a consent form before the procedure. Once the ear canal has been evaluated otoscopically, samples obtained for otic cytology and C/A, the ear flushed, and a myringotomy performed (if necessary), it is important to address the primary causes as well as predisposing and perpetuating factors associated with the otitis. Additional diagnostics may be required to determine these causes and factors. Specific treatment for any infections should be implemented immediately.

Cytology The principal value of otic cytology is identification and characterization of microbial overgrowth or infection that contributes to clinical signs and perpetuates inflammation. This information strengthens interpretation of culture and susceptibility data, guides rationale therapeutic decisions, and permits more accurate monitoring of response to treatment. Practitioners may be tempted to make conclusions based on the odour and appearance of the otic exudate rather than on cytology. For instance, O cynotis is classically associated with dry, grainy, black discharge, sometimes described as ‘‘coffee grounds.’’ In contrast, yellow or light brown discharge is reported to indicate bacterial infections, whereas waxy honey-coloured or brown exudate is associated with Malassezia. Unfortunately, these observations are not consistent or reliable. Veterinarians are cautioned to avoid relying on the physical character of discharge, odour, or past experience when making a diagnosis or selecting therapy. Rather, these decisions should be based on evidence established by careful microscopic evaluation of exudate. Failure to do so may result in inappropriate use of antimicrobial agents, failure to recognize and treat relevant pathogens, and an inability to monitor changes in pathogens on subsequent examinations. The ultimate result is poor quality of case management, prolongation of treatment, or even treatment failure and progression of disease. Veterinarians are encouraged to view cytology as a mandatory test for every patient presenting for clinical signs of otitis.

Sample preparation Separate cytologic specimens should be prepared from each ear canal, even if the patient presents for unilateral disease. This permits comparison between the diseased ear and the normal ear as well as early recognition of bacterial or yeast overgrowth in the less obviously affected ear. Independent evaluation of each ear is also necessary in patients with bilateral disease. Clinically relevant differences in bacteria and yeast are expected when comparing the two ears. Without independent evaluation, documentation, and monitoring of each ear separately, veterinarians may fail to make appropriate management decisions. Sample collection should always be performed before introduction of any cleaning agent or therapy. The sample can be most easily obtained using a clean cotton-tipped ear bud or Cytobrush introduced gently into the external canal. In most cases, material obtained from the deeper horizontal canal is more clinically relevant than material obtained from the superficial vertical canal. To obtain consistent samples without causing undue risk to the patient’s tympanum, veterinarians should aim for the junction of the vertical and horizontal canal, where the cartilage bends at an angle of 75°. In the case of otitis media, systemic therapy should be directed at organisms colonizing the tympanic cavity rather than the external canal. In one study, isolates from the tympanic

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cavity differed from isolates from the horizontal canal in 89.5% of cases. In the same study, the tympanic membrane appeared to be intact in 71.1% of the ears with proven otitis media. Once the sample is collected, roll the swab onto a clean glass slide, evenly distributing a thin layer of material. Care should be taken to identify which ear was sampled by labeling the slide. Because cerumen has high lipid content, briefly heat the slide to fix material to the glass, preventing loss of valuable information in the stain solvent. Avoid overheating the slide, because this may distort cells, bacteria, or yeast. Most morphologically coccoid bacteria found in the ear canal are gram positive organisms and most rod bacteria are gram-negative. The high-dry ×40 objective (×400 magnification) is adequate for identification of leukocytes, red blood cells, cornified epithelium, yeast, and larger bacteria. After examination of the slide with the high-dry objective, switch to the high-magnification oil immersion lens (×100 objective, ×1000 magnification) for detailed evaluation; otherwise, additional smaller or lightly stained bacteria may be missed. Higher magnification also permits better visualization of morphologic characteristics of bacteria as well as evaluation of the cytoplasm of neutrophils and macrophages for phagocytized bacteria. Evaluate each cytologic preparation for the number and characteristics of three specific features: yeast, bacteria, and leukocytes. To estimate the numbers, evaluate 5 to 10 areas; record the average count per high-powered field. A complete and consistent record of cytologic findings is necessary to monitor progression of disease or response to therapy. These details allow the primary clinician or any colleague following the case to determine if the infection is resolving, changing, or worsening.

Normal cytology Microscopic examination may demonstrate normal cornified squamous epithelial cells seen as sheets of lightly stained basophilic keratin. These cells may roll up on themselves during smear preparation, resulting in deeper staining and a shard-like appearance. Desquamated keratinocytes may contain melanin granules, which appear as tiny yellow to brown ovoid or round structures (often misidentified as small cocci). The external ear canal of dogs and cats contains small numbers of normal resident bacteria. Differentiating bacteria from debris or stain precipitate can be challenging if there are only a few organisms per field. With the exception of Corynebacterium, rod-shaped bacteria are rarely found in normal ear canals. Any bacteria found in the presence of leukocytes should be considered abnormal. Another finding on normal otic cytology is basophilic staining yeast. Characteristically, these organisms exhibit unipolar budding, which creates the commonly described ‘‘peanut,’’ ‘‘snowman,’’ or ‘‘footprint’’ shape easily recognizable as Malassezia. Although these organisms are normal residents of the canine and feline ear canal, under the appropriate circumstances, Malassezia can become important opportunistic pathogens contributing directly to severity of clinical signs as well as to progression and perpetuation of disease.

Abnormal cytology

Malassezia yeast M pachydermatis is present in 15% to 49% of normal canine ear canals and in up to 83% of dogs with otitis externa. Although more commonly isolated in the external canal, Malassezia may also colonize the tympanic cavity. In one study, Malassezia was recovered from 65.8% of external ear canals and 34.2% of middle ears of dogs with chronic otitis. When otitis media is suspected, cytologic evaluation of debris from the tympanic cavity should be performed. Because Malassezia can be found in normal patients or mixed in with predominantly bacterial infections, veterinarians need to determine the clinical significance of Malassezia for individual patients. Cytology is the most useful tool for differentiating between normal resident colonization and overgrowth. Unlike bacterial infections, suppurative inflammation is not a common feature of Malassezia otitis and thus cannot be used to determine a pathologic state. A recent study by Ginel et al proposed using semiquantitative criteria for the diagnosis of significant yeast otitis. By comparing cytologic specimens from normal and diseased ears, the authors concluded that 2 or fewer yeast

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organisms per high-dry field (×40 objective, ×400 magnification) in the dog and cat was normal. Mean counts of 5 or more yeast organisms per field in dogs and 12 or more yeast organisms per field in cats were abnormal. The intermediate values were considered a grey zone. Using these values to diagnose otitis externa, cytology had a specificity of 95% in dogs and 100% in cats. The sensitivity was only 50% for dogs and 63% for cats because of the fact that some cases of otitis externa were exclusively bacterial with minimal yeast involvement. Semiquantitative estimation of numbers provides a guideline for the clinician, but, ultimately, the decision to treat or not to treat Malassezia depends on a combination of cytologic findings, severity of clinical signs, past history of yeast otitis, and previous response to therapy in the individual patient.

Bacteria The most common pathogens associated with otitis externa are coagulase-positive staphylococci, B-hemolytic streptococci, Pseudomonas spp, and Proteus spp. Although the same classes of bacteria are frequently isolated from the tympanic cavity, there may be considerable variability between the two locations within the same patient. In a study comparing isolates from the horizontal canal and the tympanic cavity of dogs with chronic otitis externa and media, there were differences in the species or antimicrobial susceptibility of bacteria isolated in 89.5% of the cases. Therefore, samples for cytology and culture should be obtained from the tympanic cavity rather than from the external canal. The distinction between bacterial ‘‘overgrowth’’ and ‘‘true infection’’ is subtle but clinically important. In general, overgrowth of bacteria in the debris and on the epithelial surface of the external canal does not warrant culture and susceptibility testing or expensive systemic therapy. Systemic therapy is not necessarily more effective for these cases, because the concentration of antibiotic achieved by topical medications can far exceed that achievable by systemic routes. In contrast, in the case of bacterial infection of the tissue of the external canal or within the tympanic cavity, high-dose long-term systemic antibiotic therapy is necessary for successful resolution Based on the results reported by Ginel et al, 5 or fewer bacteria per high-powered dry field (×40 objective) should be considered normal, whereas 25 or more bacteria per field suggests an abnormally increased population, with the intermediate numbers in a grey zone subject to interpretation. For cats, 4 or fewer bacteria per field was consistent with normal and 15 or more bacteria per field was abnormal. Using these mean count criteria to differentiate normal from diseased ears yielded 95% specificity and 50% sensitivity in dogs and 100% specificity and 63% sensitivity in cats. Another important piece of evidence supporting a diagnosis of infection versus overgrowth is the presence of abundant leukocytes on cytology. Leukocytes are not found in the normal canal, nor are they frequently present during overgrowth of organisms on the surface of the external canal. The best method for diagnostic evaluation of bacterial otitis is cytology in combination with culture and susceptibility testing. Cytologic evidence is available immediately, allowing the veterinarian to initiate rational empiric therapy while awaiting susceptibility results. When the laboratory report arrives later, knowledge derived from cytology determines which organisms are most relevant, directing alterations in the initial plan.

Leukocytes In addition to evaluating cytologic preparations for bacteria and yeast, otic exudate must be carefully examined for white blood cells. Although yeast and bacteria are normal findings, leukocytes should not be present in otic cytology from normal patients. Neutrophils, macrophages, and other inflammatory cells only gain access to the lumen of the canal as the result of exudative inflammation, ulceration of the epithelial lining, or extension from the tympanic cavity during otitis media. Thus, finding leukocytes on cytology suggests a more severe disease process. If the immune system is responding to an infection with suppurative or pyogranulomatous inflammation, systemic antibiotic therapy is almost always indicated. In many patients with otitis externa, the only evidence of concurrent otitis media during the initial evaluation is extension of purulent exudate from the tympanic cavity into the external canal. Because otitis media is present in 16%of dogs with acute otitis externa and in up to 82% of dogs with chronic disease, any cytologic evidence of leukocytes in the external canal should increase the clinician’s suspicion for concurrent otitis media, warranting specific diagnostic evaluation. When appropriate, culture and susceptibility samples should be obtained directly from the middle ear. If leukocytes are present

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during initial evaluation, the disappearance of leukocytes from subsequent cytology is a clear indication of response to therapy and movement toward resolution.

Causes otitis externa During the early stages of acute otitis externa, the underlying process causing inflammation of the external ear canal initially results in varying degrees of erythema of the pinnae, external meatus, and lining of the external canal. Subsequently, there can be a wide range of clinical signs, including head shaking, ear scratching, otic discharge (ceruminous or purulent), evidence of self-trauma and excoriations (including aural hematomas and acute moist dermatitis near the base of the ear), malodor, swelling, and pain. In cases of recurrent or chronic otitis externa, these clinical signs may progress to include proliferative changes such that the external ear canal becomes stenotic and is ultimately occluded; at that time, the tympanum becomes more susceptible to rupture and the development of a concurrent otitis media. This chronic inflammation is also associated with hyperplastic changes of the soft tissues surrounding the external ear canal. When the underlying problems are not addressed and identified, these chronic, hyperplastic, soft tissue changes may progress to the development of fibrosis and mineralization of the tissues surrounding the external ear canal. At this stage, medical treatment is invariably unsuccessful, requiring some form of additional surgical treatment. In addition, the lining of the external ear canal may develop erosions and ulcerations, resulting in a marked increase in pain of the canals.

Primary causes These causes are defined as processes or factors that directly initiate the inflammation of the external ear canal. The successful treatment of the patient thus requires specific identification and treatment of this process.

1. Parasites Otodectes cynotis (ear mite) has been reported to account for up to 50% of cases of otitis externa in cats and 5% to 10% of cases in dogs. Initially, the exudate is usually a dark brown to black color; however, chronic cases may become secondarily infected with bacteria or yeast; at that time, the exudate may develop more ceruminous or purulent characteristics. Demodex canis may infrequently cause a ceruminous otitis externa in dogs (with or without concurrent skin lesions of demodicosis), and Demodex cati may infrequently cause a ceruminous otitis externa in cats.

2. Foreign bodies Plant awns can be a cause of otitis.. Plant awns are capable of migrating into the deepest portion of the horizontal ear canal and rupturing the tympanum, resulting in a concurrent otitis media. Less frequently observed foreign body reactions may be induced by dirt, sand, dried otic medications, broken/loose hairs, and dead insects .

3. Allergic skin disease In dermatology referral practice, greater than 90% of the cases presented for chronic/recurrent bilateral otitis externa (and occasionally unilateral disease only) are a result of the presence of atopic dermatitis or food allergy in dogs. In most instances, the history and physical examination indicate the presence of inflammation and pruritus on other areas of the body associated with the potential problem of atopic dermatitis or food allergy. These areas include the face (especially the muzzle and periorbital regions), feet, inguinal/ventral abdominal region, axillary region and flexural surfaces of the foreleg (elbow and carpus). It has been reported that up to 55% of dogs with atopic dermatitis have concurrent otitis externa, with 3% to 5% of cases exhibiting otitis externa as the only clinical sign. Additionally, up to 80% of dogs with food allergy have concurrent otitis externa, with 25% of cases exhibiting otitis externa as the only clinical sign.

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4. Keritinization disorders Endocrine disorders, such as hypothyroidism, hyperadrenocorticism, and sex-hormone imbalances, may alter keratinization and cerumen gland production in the external ear canal, resulting in an initial ceruminous and seborrheic form of otitis externa. A similar form of otitis externa may occur in cases of sebaceous adenitis and idiopathic seborrhea.

5. Autoimmune disease The autoimmune skin diseases that may affect the pinnae or the external ear canals include pemphigus foliaceus, discoid lupus erythematosus, cutaneous vasculitis, bullous pemphigoid, and mucous membrane pemphigoid. These are all relatively rare causes of otitis externa, and, invariably, there are skin lesions at other locations of the body or lesions on various mucous membranes.

Predisposing causes These causes are defined as processes or factors that increase the risk of developing otitis externa and work in concert with the primary or perpetuating causes of otitis externa to cause clinical disease. It is important to recognize and possibly control these problems as a part of the complete therapeutic plan.

1. Anatomic and conformational factors These factors include dogs with long pendulous ears, stenotic ear canals, and excessive hair in the external ear canal. It is controversial as to whether or not such conditions alone can cause otitis externa.

2. Excessive moisture An excess accumulation of water from frequent swimming or bathing can lead to maceration of the stratum corneum lining the external ear canal. This removes the protective barrier to secondary infection, and the normal resident microflora of the external ear canal can become opportunists, causing a subsequent otitis externa. This frequent wetting of the ear canal may also stimulate the activity of the ceruminous glands, causing a ceruminous otitis externa.

3. Iatrogenic factors These factors include the use of cotton-tipped swabs for ear cleaning, traumatic removal of hair from the ear canal, inappropriate topical or systemic antibacterial treatment predisposing to resistant strains of opportunistic bacteria, and the use of known irritating solutions.

4. Obstructive ear disease Inflammatory polyps and tumours of the ear canal prevent exudate drainage, which predisposes the ear to secondary infection.

Perpetuating causes of otitis externa These causes are defined as processes or factors that are not responsible for the initiation of the otitis externa but do cause the disease to continue once established. Once present, these causes must be specifically treated, but always in conjunction with treatment of the associated primary and predisposing causes.

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1. Bacteria It is important to emphasize that the external ear canal has a low number of resident as well as transient bacteria present under normal circumstances, and culture of the normal external ear canal has been reported to include Staphylococcus pseudintermedius, Pseudomonas spp, Streptococcus spp, and Proteus spp. Once overcolonization of the external ear canal occurs, the most commonly isolated bacterial pathogens include S pseudintermedius, Pseudomonas aeruginosa, Proteus mirabilis, Escherichia coli, Corynebacterium spp, Enterococcus spp, and Streptococcus spp. In cases of chronic or recurrent bacterial otitis externa, the most common problematic opportunistic pathogen is invariably P aeruginosa.

2. Yeast Similarly, it is important to emphasize that the external ear canal has a low number of resident yeast present under normal circumstances and that culture of the normal external ear canal may reveal the presence of Malassezia pachydermatis. Once overcolonization of the external ear canal occurs, the most commonly isolated fungal pathogen is M. pachydermatis, with the occasional isolation of Candida spp.

3. Otitis media Inflammation and infection of the middle ear cavity often play an important role in cases of chronic or recurrent otitis externa. Such infection usually develops as an extension of otitis externa through a ruptured tympanic membrane but may also be present in instances where the tympanic membrane is noted to be intact. Inflammation and infection of the middle ear cavity may also occur from potential pathogens in the nasopharynx via extension through the auditory tube (Eustachian tube) or, rarely, via hematogenous spread.

Investigating chronic otitis The first step in investigating the chronic ear is to make the distinction between a SURGICAL ear and the MEDICAL ear. This is a fundamemntal step and in any chronic ear, making this distinction early saves time, suffering and money. “Chronic” is defined as otitis present for more than 2 months or as recurrent disease over a period of 6 months or more. The primary factors must be identified and managed. If they are not the end result will inevitably be total ear canal ablation (TECA) normally with a lateral bulla osteotomy (BO). Remember what these primary factors are – they initiate ear canal inflammation and include parasites, allergies, foreign bodies, endocrinopathies autoimmunities and polypoid masses. The perpetuating factors will prevent resolution of disease and will need to be addressed in the immediate and short term (these include bacteria, yeast and otitis media. It is important to remember that bacteria and yeats are not primary causes of chronic disease. Never forget the role that otitis media plays in chronic disease (this is traditionally underestimated). If primary causes are not addressed recurrent infections will result and the ear canal pathology may get to the point of being irreversible. Irreversible damage to the canal will necessitate surgical removal (TECA-BO). The old so called “Zepps” operation is no longer used or indicated. The first question that must be settled in any case that is chronic is, “Is this a surgical candidate or not?”. If it is not, the perpetuating factors must be resolved (infection, otitis media) and an investigation into the primary factors must be instigated. The indications for surgery are:

1. Severe calcification of the ear canal cartilages 2. Irreversible soft tissue pathology 3. Bony changes in the tympanic bulla 4. Persistent infection of the middle ear 5. When a dog has become completely averse (aggressive) towards the owner applying topical

treatments, this would normally also indicate a surgical ear. Calcification and bony changes are determined on radiographs and/or (preferably) computed tomography scan (CT). Irreversible soft tissue changes cause ear canal stenosis that is unresponsive to 4 week of anti-inflammatory

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treatment. The degree of stenosis is regarded as sever if the tympanic membrane is not easily visualised, if you cannot perform cytology and culture of the middle ear and if the ear canal cannot be cleaned and treated. Severe hyperplastic changes should be treated with between 1 and 4 weeks of glucocorticoids topically and systemically. Systemic prednisolone can be given on a declining dose starting at 1mg/kg bid for 3 days, then 1 mg/kg oid for 5 d then 0.5 mg/kg oid for a week and then on an alternate day basis. Topical glucocorticoids can be used with commercially available ‘poly-pharmacy’ otic preparations or dexamethasone can be made up in a 1:1 dilution (2mg/ml dexa mixed 1:1 with saline). Daily cleaning can be considered if the animal will tolerate it. It is crucial that any cleaning procedure not become painful as the animal will become to head shy to treat and that will then almost certainly necessitate surgery. A typical ‘plan’ for a case of chronic disease would look something like this: Day 1:

ALWAYS consider the skin as a whole and never just focus on the ear disease alone. Almost all allergic skin disease that effects the ears will also show clinical disease on the skin (axillae, groin, feet, palmar surfaces). The owner will usually complain of pruritus elsewhere besides the ears. The skin as a whole will need to be managed (antibiotics, shampooing) and assessing response to treatment or diagnostic trials will involve the owner scoring the skin disease as a whole, not just the ears. I always perform a CT of the head to rule out calcification of the ear canal and/or bony changes to the bullae. If these are present I do not proceed any further with medical treatment but recommend a TECABO straight away. Sadly, because few ears are worked up well to start with, the majority of chronic ears I see are beyond salvaging. Determining the reversibility of ear canal swelling (if the imaging provides n evidence of a surgical ear) requires a course of high dose glucocorticoids (7-10 days) followed by reassessment. If oedema or proliferative changes preclude visualization of the entire canal to the level of the tympanum, topical therapy should be initiated based on cytologic findings, and the patient should be discharged on an anti-inflammatory regimen or oral prednisolone Determining the PRIMARY cause in a chronic ear that is going to be medially managed is absolutely mandatory. I always start a novel protein dietary trial at this point (lasting 8 weeks with strict instructions on how to conduct this). Always emphasise to the owner that a well conducted dietary trial can never fail; if it is well done, the results are always useful. ‘Failure’ simply means food allergy is not playing a significant role. Partial success means food allergy is playing some role – and atopy is more than likely the remaining contributing factor. A good response obviously means food allergy.

Day 14-28 The ear canal should be open. At this point a general anaesthetic is given, the ears are imaged (radiographs, CT) Imaging and ear canal examination will determine at this point whether or not this is a surgical case or not. If it is surgical, proceed no further medically, perform a TECA-BO. If it is not a surgical candidate the canal should be tested cytologically, samples should be collected for culture and anibiogram, the external ear canal should be cleaned (flushed) and the middle ear evaluated by myringotomy Treatment with second-line or third-line antimicrobials may be indicated depending on the history of prior therapies. The client should be prepared for longer term topical therapy (at least 4 weeks in duration). In extremely chronic cases, several months of rigorous topical therapy may be necessary to return the external canals to their normal state. Systemic antibiotics may be indicated if there is extensive tissue swelling (potentially indicating deeper infection), ulceration, or significant periaural dermatitis. Rechecks should be scheduled every 2 to 4 weeks for cytologic and otoscopic examination until complete resolution is achieved.

Day 60 At this point the effect of the diet trial to control ear canal inflammation must be established. Should the food trial diagnose atopy, a discussion with the owner around the long term control of atopy will be necessary. The three options are typically occasional short term, lowest possible dose

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glucocorticoids (as long as the dog remains side effect free); life-long cyclosporine; allergen specific immunotherapy.

Diagnostic imaging

Radiographs Radiographs are useful for evaluating the osseous tympanic bulla. Additionally, the external ear canals can be evaluated for chronic changes, such as mineralization or stenosis. Radiography is a widely available imaging modality familiar to veterinarians and is often the initial modality used for the evaluation of ear disease.

Technique and positioning General anesthesia is necessary to achieve adequate positioning when making radiographs for evaluation of the tympanic bulla. Without general anaesthesia, it is not be possible to make a complete radiographic study. Radiographic evaluation of the tympanic bulla includes lateral, dorsoventral, or ventrodorsal; latero-20° ventral-laterodorsal oblique; and rostro-30° ventral-caudodorsal open-mouth oblique radiographs.

Radiographic appearance of disease states

Otitis externa The ventrodorsal view has been described as best for evaluating a patient for otitis externa. Radiographic findings with otitis externa include stenosis or mineralization of the wall of the ear canal. Additionally, abnormal soft tissue opacity replacing gas in the external ear canal can be visualized.

Otitis media The latero-20° ventral-laterodorsal oblique and rostro-30° ventral-caudodorsal open-mouth oblique radiographs are best for evaluation of the tympanic bullae. Radiographic findings associated with pathology of the middle ear include soft tissue opacity in the bulla, sclerosis of the wall of the tympanic bullae or petrous temporal bone, bony proliferation of the petrous temporal bone, and signs of otitis externa. If the infectious process is severe enough, lysis of the tympanic bullae can also be visible.

Nasopharyngeal polyps The latero-20_ ventral-laterodorsal oblique and rostro-30° ventral-caudodorsal open-mouth oblique radiographs are best for evaluation of the tympanic bullae, whereas a lateral view allows evaluation of the nasopharyngeal canal. Radiographic findings of unilateral or bilateral increased soft tissue opacity within the tympanic bulla and sclerosis of the osseous bulla are suggestive of nasopharyngeal polyps. Additional signs that can be seen with nasopharyngeal polyps are findings of otitis externa and soft tissue opacity in the horizontal ear canal. Nasopharyngeal polyps may also cause nasopharyngeal obstruction, seen radiographically as increased soft tissue opacity in the nasopharyngeal region.

Neoplasia Neoplasia within the tympanic bulla can produce radiographic findings of soft tissue opacity within the tympanic bulla and sclerosis of the osseous bulla. Some neoplastic processes lead to lysis of the osseous bulla. Radiographic findings associated with neoplasia within the external ear canal include a soft tissue mass effect around the external ear canal with impingement or obliteration of the external ear canal. Aggressive neoplasms, including squamous cell carcinoma and mucinous gland adenocarcinoma, can result in obliteration of the external ear canal as well as lysis of the adjacent calvaria.

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CT CT evaluation of the ear canal is particularly useful for cases of otitis media. It is also useful for the evaluation of nasopharyngeal polyps and unilateral or bilateral otitis externa and to determine the extent of neoplasia. Additionally, CT is used to evaluate the communication of fistulous tracts and abscesses with the external ear canal. At the Onderstepoort Veterianry Academic Hospital CT scanning of the head has become a standard part of the investigation of chronic otitis externa and radiographs are seldom used for this purpose.

Medical therapy of otitis The medical approach to therapy of otitis externa and media may currently be best described as an art rather than a science. Although the veterinary literature evaluating diagnostic techniques for otitis has grown considerably in the past few years, veterinary studies documenting medical therapies (beyond ototoxicity research) are quite scarce. Because dermatologists deal with otic infections on a daily basis, this group of specialists has contributed much to the anecdotal knowledge base on the subject. Multiple approaches are routinely discussed, which often vary in the empiric choices of topical drugs and cleansers employed, the frequency and technique of ear canal lavage (both in-office and as administered by the pet owner at home), and the types and frequencies of prophylactic therapies recommended after resolution of chronic infections. One point of agreement (and much concern) is the growing evidence for multidrug-resistant strains of Pseudomonas aeruginosa and methicillin resistant Staphylococcus spp.

Topical versus systemic therapeutics Topical therapy is key to the successful resolution of otitis externa, which is essentially a surface infection. Unless the ear canal epithelium has been eroded or ulcerated extensively, systemic (oral) antimicrobials are unlikely to achieve therapeutic concentrations within the fluid and waxy exudates of the external canals in which the infectious organisms are harboured. Penetrating this ‘‘vat’’ of infection is best accomplished by the application of sufficient volumes of a topical antimicrobial. The choice of active ingredients for treatment of otitis externa is usually made empirically, based on cytologic examination of ear canal exudates and otoscopic examination of the inflamed canals. In contrast, the middle ear (tympanic bulla) contains a highly vascular mucous membrane lining, which may allow for better diffusion of drugs from the vascular compartment to the bulla space. The choice of systemic antibiotics for treating the middle ear compartment is preferably based on culture and susceptibility testing. Despite this, topical therapy in otitis media remains crucial in most cases. Information gleaned from culture and susceptibility testing reflects the serum level of drug required to kill the organism in question and may not be relevant in choosing topical antimicrobial preparations. Susceptibilities are typically expressed as minimum inhibitory concentrations (MICs) or reported simply as ‘‘susceptible,’’ ‘‘intermediate,’’ or ‘‘resistant’’ based on the Kirby-Bauer disk diffusion method. For several reasons, this in vitro information may relate poorly to the choice of topical antimicrobial. As already mentioned, adequate levels of drug (which reach the MIC for the organism) may not be achieved at the surface of the external ear canal epithelium. In addition, the concentrations of specific antimicrobial ingredients in topical preparations often greatly exceed those that could be safely achieved in the systemic circulation. For example, an organism that is reported to be resistant to gentamicin on a culture/susceptibility test may not be resistant to the high concentration of gentamicin that can be safely delivered locally within the ear canal itself. Finally, not all active ingredients used topically are represented on standard culture/susceptibility profiles. Therefore, veterinarians should be comfortable with basing an empiric choice of topical antimicrobial on the cytologic identification of the organism (or class of organism) and otoscopic evaluation of the extent of ear canal inflammation and chronic changes.

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Ingredients of topical antibacterials Most commercially produced topical products contain one or more active ingredients (antibacterial, antifungal, and anti-inflammatory) in various combinations as well as a vehicle and various solubilizers, stabilizers, and surfactants. The formulation of the topical product with regard to the vehicle may be as important as the active ingredient to the success of therapy. Vehicles are chosen to maximize drug solubility, to maintain drug activity locally for the maximum period, and to minimize systemic absorption. The most commonly used vehicles are water (which may be buffered and pH adjusted to maximize drug activity), demulcents, and emollients. Demulcents are compounds of high molecular weight capable of forming stable emulsions or suspensions of drugs that are not water soluble. They coat and protect underlying tissue. Polyhydroxy demulcents, which are the most hydrophilic yet potentially irritating compounds within this class, are also the most commonly used carriers used in otic products. They include polyethylene glycol, propylene glycol, and glycerine. The former two are commonly implicated in contact/irritant reactions. Emollients are occlusive agents used as carriers for water-insoluble drugs and are protective and hydrating to the stratum corneum. Examples include vegetable oils, animal fats (eg, lanolin), and hydrocarbons (eg, petrolatum, mineral oil, paraffin). Active ingredients are generally classified as antibacterials, antifungals, and anti-inflammatories.

Antibacterials

Aminoglycosides The aminoglycoside antibiotics are the most commonly used class of topical otic products. They act on susceptible bacteria by binding to the 30s ribosomal subunit in the bacterial nucleus, thereby inhibiting protein synthesis, and are considered to be bactericidal. Their antibacterial spectra vary by individual drug potency but include some aerobic gram-positive bacteria and many aerobic gram-negative species. They are ineffective for anaerobes and fungi. Their antimicrobial activity is enhanced in an alkaline environment, which is germane to topical therapy of the ear canal. If acidifying cleansers are used in conjunction with aminoglycosides, the products should be applied at least 1 hour apart. Also of noted importance is the ototoxic potential of aminoglycosides, especially when administered parenterally. Auditory symptoms are more common with neomycin and amikacin, whereas vestibular symptoms are most typical of gentamicin, especially in the cat. The ototoxic potential of this class of drugs when topically applied may be overestimated.

Neomycin Often considered to be a first-line topical antibacterial, neomycin has the lowest potency of the class, showing significantly less efficacy against several gram-negative organisms; most notably Escherichia coli and P aeruginosa. Its activity against gram-positive cocci remains quite good. Manufactured topical products containing neomycin are plentiful and are recommended for acute bacterial otitis in which cocci predominate cytologically.

Gentamicin Considered to be a ‘‘second-line’’ antibacterial, gentamicin has intermediate potency within the class. Its activity against gram-positive cocci is excellent; however, resistant strains of E coli and P aeruginosa are not uncommon. Manufactured topical products containing gentamicin are plentiful and are recommended for chronic/recurrent otitis when clinical evidence of neomycin-resistant rods is available. In general practice, these products are often used as first-line antibacterials. Despite continuing anecdotal concern over the ototoxic potential of topical gentamicin, a study in dogs designed to simulate clinical exposure via a ruptured tympanum failed to document any toxicity

Amikacin Considered to be a third-line antibacterial, amikacin is most commonly indicated for chronic/recurrent otitis caused by gentamicin resistant gram-negative bacilli (especially P aeruginosa). Amikacin is not available as a

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commercially produced topical product, but the injectable product is often diluted to a concentration of 30 to 50 mg/mL (in sterile saline or a tromethamine–ethylenediamine-tetraacetate [Tris- EDTA] product) by veterinarians for topical use.

Tobramycin Also a third-line antibacterial, indications for use of tobramycin are similar to those for amikacin. Although an otic topical product is not available, ophthalmic formulations are. Dilution of injectable tobramycin with sterile saline to a concentration of 8 mg/mL has been used, but the long-term stability (>1 week) of the solution is unknown and remains a concern.

Fluoroquinolones This class of antibiotics acts by inhibiting bacterial DNA-gyrase, which prevents DNA supercoiling and synthesis and is thus bactericidal. Bactericidal activity is dependent on concentration, and bacterial resistance is known to occur by rapid mutation, especially in the presence of subtherapeutic concentrations. Fluoroquinolones have good activity against a wide range of gram-negative bacilli and gram-positive cocci (including staphylococci, although activity is variable for streptococci). Their use as second- or third-line antibiotics for chronic/recurrent bacterial otitis, especially cases associated with P aeruginosa, has become common. Studies comparing two human-labeled topical fluoroquinolone products (ciprofloxacin and ofloxacin) with polymyxin B have shown the fluoroquinolones to be safe, with less ototoxic potential.

Carboxypenicillins This class includes the expanded-spectrum penicillins, which exhibit activity against gram-negative organisms (including Pseudomonas spp) because of their ability to penetrate the gram-negative cell membrane. Ticarcillin is the carboxycillin for which topical use has been most commonly reported in the treatment of canine Pseudomonas otitis. One pair of authors recommends dilution of the 6-g bottle with 12 mL of sterile water and the addition of reconstituted ticarcillin, 2 mL, to 40 mL of an acidifying ear cleanser (with the remainder frozen for future use). The stability of this solution is unknown but may not exceed 3 days.

Polymyxins Polymyxin B and colistin sulfate (polymyxin E) are polypeptide antibiotics that exert bactericidal effect by increasing permeability of the bacterial cell membrane via chelation of membrane phospholipid components, leading to osmotic damage. The ototoxic potential of polymyxin B has been well described experimentally in several species of animals, both in vivo and in vitro. There is speculation that the ototoxicity of these products could be more specifically attributable to the propylene glycol vehicle, however. One positive aspect of topical polymyxin B is its reduction of the inflammation induced by endotoxin components of gram negative bacterial cell walls. The relevance of these findings to dogs and cats is unknown.

Silver sulfadiazine Used for more than three decades in human medicine as a burn wound protectant, silver sulfadiazine (SSD) has broad-spectrum antibacterial activity (most notably against P aeruginosa) and does not interfere with re-epithelialization and neovascularization of wounds. In fact, it may enhance wound healing. The spectrum of activity includes most pathogens associated with otitis (including methicillin-resistant staphylococci), with the exception of Malassezia pachydermatis, against which activity is low. Resistant strains of P aeruginosa have been reported but are extremely rare. Silver exerts its antibacterial effect via impairment of DNA replication and bacterial cell wall damage, leading to osmotic changes. Although the cream is not readily miscible in water, a homogeneous emulsion can be achieved with gentle mixing. SSD has become the favored topical therapy for Pseudomonas otitis in the, especially when the external ear canals are ulcerated. The ototoxic potential of SSD is unknown, although the collective experience of a large group of veterinary dermatologists suggests that it is safe for use even in the context of a ruptured tympanum. Because it is known that significant amounts of silver can be absorbed from burn wounds of human beings and silver has the potential to produce systemic toxicity, caution may be warranted in veterinary patients with extensive ulceration. Evidence implicating SSD in systemic toxicity of dogs or cats has not been, and a 1% suspension has been used in scores of dogs and several cats for more than 3 months without incident at the University of Pennsylvania.

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Tromethamine–ethylenediamine-tetraacetate (EDTA) This is commonly used as either a pre-soak or a carrier vehicle (for aminoglycoside antibiotics) in the treatment of gram-negative infections. EDTA promotes increased permeability to extracellular solutes and increased sensitization to antibiotics, whereas Tris serves as a buffer.

Antifungals

Nystatin A polyene antifungal, nystatin binds to sterols in the fungal cell membrane, thereby altering permeability and mediating cell death by osmotic destruction. Nystatin is primarily used to treat infections by Candida spp, but it also exhibits activity against M pachydermatis clinically. Because most preparations containing nystatin are occlusive ointments, I may be better to avoid using them in cases of exudative or ceruminous otitis externa (fairly typical for Malassezia otitis).

Azole antifungals Benzimidazoles (eg, thiabendazole), imidazoles (eg, clotrimazole, miconazole, ketoconazole), and triazoles (eg, itraconazole, fluconazole) all share a common mode of action against fungi: disruption of cell wall ergosterol biosynthesis via P450 enzyme inhibition. An in vitro study comparing the efficacy of the azoles against Malassezia spp yeast indicated that thiabendazole is the least effective, followed by clotrimazole (with efficacy comparable to nystatin), miconazole (with 10 times the potency of nystatin), ketoconazole, and itraconazole, respectively]. A more recent in vitro study showed equal efficacy of ketoconazole, itraconazole, and terbinafine against M pachydermatis, whereas a Hungarian study suggested that ketoconazole is the most effective, followed by clotrimazole, miconazole, and nystatin, respectively. Veterinary topical preparations of thiabendazole, clotrimazole, and miconazole are commonly employed for the treatment of Malassezia otitis in dogs and cats. Ketoconazole is available only under human labels as oral tablets and a topical cream. Both may be used to formulate 1% to 2% solutions for otic treatment of veterinary patients when other more available azoles are failing clinically. Miconazole is the topical agent most commonly employed against Malassezia otitis. Topical azole antifungals are said to be uniformly nontoxic to the inner ear. Although antifungal ototoxicity does not seem to be clinically problematic in dogs and cats, contact/irritant reactions may be noted with any of the azoles. It is difficult to exclude the role of vehicle versus the azole drug in many cases, however. Oral ketoconazole or itraconazole may be used for canine otitis media associated with Malassezia spp, whereas itraconazole is generally preferred for this purpose in cats.

Anti-inflammatory agents Almost every case of otitis deserves the benefits of topical corticosteroids because of their anti-inflammatory, antiproliferative, antipruritic, and antiexudative (glandular secretory) effects. Systemic steroids [preferably prednisolone] are also highly efficacious in reducing acute stenosis caused by oedema as well as more chronic stenosis caused by proliferative hyperplasia and fibrosis. Topical steroids are present in a large proportion of commercially prepared otic products, and their potency may depend not only on the drug’s inherent anti-inflammatory quotient but on the drug concentration and vehicle used in the product. In general, the potency of topical steroids is assumed to concur with their biologic activities. Relative potencies compared with hydrocortisone are: hydrocortisone (1), prednisolone (5), triamcinolone (5), dexamethasone (25), betamethasone (25), and fluocinolone (100). Some authors believe that nothing more potent than hydrocortisone should be used in cases of ulcerative Pseudomonas otitis. Side effects related to topical steroids include systemic absorption with suppression of the hypothalamic-pituitary-adrenal axis (which likely increases with the higher potency steroids).

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The only nonsteroidal agent used in a topical otic preparation is dimethyl sulfoxide (DMSO). In addition to its significant anti-inflammatory activity, DMSO may reduce fibroplasia. Topical ear formulations with DMSO are not available in RSA.

Therapy of acute otitis externa In general a first-line antimicrobial should be chosen based on cytologic and otoscopic findings. Twice-daily therapy for a minimum of 7 to 14 days depending on the degree of inflammatory changes (oedema, hyperplasia, and erosion/ulceration) combined with at-home cleansing is the prescribed regimen. Of utmost importance is delivering a sufficient volume of topical agent to the canal. For example, large-breed dogs (eg, retrievers, shepherds) should receive a minimum of 10 to 12 drops (or 1 mL) per application. Re-evaluation at the end of the regimen to evaluate the cytologic and otoscopic status of the ears is recommended but not mandatory for success in most cases.

Otitis media Otitis media, an inflammatory disease in the middle ear cavity, is a common disease process that goes unrecognized in most veterinary practices. Otitis media in dogs is much more prevalent than previously thought. In dogs, secondary otitis media occurs in approximately 16% of acute otitis externa cases and in as many as 50% to 80% of chronic otitis externa cases. The fact that otitis media is present in more than half of canine patients with chronic otitis externa should stimulate a reformulation of the thought process when faced with these cases. Just the common history that the patient has been treated repeatedly for ear infections should alert the veterinarian to think about otitis media as a possibility. Otitis media should also be considered when the veterinarian is presented with a patient showing any neurologic disease affecting the head, including vestibular disease, Horner’s syndrome, or facial nerve damage. The diagnosis of otitis media in dogs can be quite difficult to make because of the long, bent, funnel-shaped conformation of the dog’s ear canal, which makes it hard to see the tympanic membrane (TM). In addition, many patients with otitis media have an intact TM, giving the clinician the impression that there is nothing wrong in the middle ear. Most canine patients with otitis media also have chronic otitis externa with pathologic changes to the ear canal that cause stenosis, making visual examination of the TM impossible. It is often theorized that otitis media is an extension of otitis externa that was not treated, improperly treated, or resistant to treatment. The end result is significant damage resulting in porosity to the eardrum over time. The diagnosis of otitis media in cats may be easier to determine with the otoscope because of their relatively short ear canals. Otitis media in cats most often results as a sequela to respiratory disease; thus, a history of sneezing, ocular discharge, or nasal discharge may aid in providing a clue. Some cats with otitis media also have a visible polyp in the ear canal after the ear is cleaned of the dried exudates and mucus. Many feline otitis media patients have a dark, dried, crumbly exudate in the ear canal that mimics an ear mite infestation. The diagnosis of OM is based on otoscopy and diagnostic imaging (as described elsewhere. Myringotomy is an especially useful technique as is briefly described below:

Myringotomy To diagnose patients with otitis media, it is sometimes necessary to perform a myringotomy to get a cytology specimen and to allow for culture and antibiotic sensitivity testing on the material trapped behind the eardrum. If there is fluid pressure pushing on the eardrum or negative pressure retracting the eardrum, perforation of the eardrum using a controlled myringotomy incision immediately relieves the intense pain associated with these pressure changes. To perform a myringotomy, the patient is anesthetized and the external ear canal is thoroughly cleaned with a disinfectant, such as dilute povidone iodine. The ear canal is then dried using suction. A sterile rigid polypropylene catheter (a tom cat catheter is suitable) is cut to an angle of 60° with a surgery blade to provide

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a sharp point. A long spinal needle can also be used to puncture the eardrum. The tip of the cut catheter is advanced under good visualization, and the pars tensa is punctured at either the 5-o’clock or 7-o’clock position to remain away from the germinal epithelium and blood vessels overlying the manubrium of the malleus. Fluid under pressure may freely flow into the horizontal canal as the perforation begins, and it should be suctioned to ensure that the myringotomy incision is large enough to accommodate a 3.5- or 5-French catheter. In the case of suppurative otitis media, myringotomy serves to decrease the fluid pressure behind the eardrum. The fluid escapes into the external ear canal and may continue to drain for several days; thus during therapy, the ear canals need to be flushed to remove this debris. The catheter is advanced through the incised TM and directed ventrally into the bulla, and gentle suction is used to retrieve any material within the bulla. If a spinal needle was used, the stylet is withdrawn before suctioning. If the bulla is dry, 1 or 2 mL of normal saline can be infused into the bulla and then immediately retrieved. This material is submitted for cytology, bacterial culture, and antibiotic sensitivity.

Treatment of otitis media Planning treatment of otitis media requires a stepwise protocol for maximal effect. An organized approach allows the clinician to formulate treatment or to change existing treatment based on observations. The steps outlined provide a framework for treating otitis media:

1. Access middle ear. 2. Perform cytology and bacterial culture. 3. Flush bulla. 4. Infuse topical medications into the bulla. 5. Reduce inflammation with corticosteroids. 6. Administer systemic and topical antimicrobials. 7. Recheck weekly, and retreat two to three times. 8. Consider surgery.

It is important to obtain samples for cytology and bacterial culture. Many infections are polymicrobial, including mixed infections of bacteria (rods or cocci) and yeasts. Cytology of a middle ear specimen may reveal Malassezia yeasts, which would not be reported if only bacterial culture was submitted to the laboratory. Additionally, cytology may not reveal bacteria because they are often protected from the cytology stains by mucus. Many cytologically negative specimens have been reported as culture-positive. In ear disease, laboratory assessment based on culture and sensitivity does not always correlate to clinical response

Flushing and suctioning the bulla The most important technique for treating otitis media is probably flushing the bulla. Topical otic medications cannot penetrate through the thick exudate that fills the middle ear during otitis media; thus, this exudate and secretory material must be removed. Additionally, many destructive enzymes that are trapped in the mucoid secretions in the bullae remain in contact with the mucoperiosteum, which prolongs the disease. Hydrating the mucus with the water in flushing solutions makes it less dense and easier to suction. Using fluid under pressure to irrigate the bulla loosens mucus from the tissue. This material does not stick to the mucous membrane as cerumen sticks to the epithelium in the external ear canal. A useful fluid used for flushing the bulla is warmed extremely dilute povidone iodine solution in warm tap water. If there is an identifiable bacterial infection, warmed Tris- EDTA is also infused into the bulla. Acidic solutions should be avoided in the middle ear so as to prevent pain and irritation. Using a device that delivers the fluid under high pressure allows the mucus and pus to flush out of the bulla either into the external ear canal, where it can be suctioned out, or through the auditory tube into the throat.

Bulla infusion Removal of the mucus and pus within the tympanic bulla during the treatment of otitis media allows topical medications to penetrate in and around the thickened and folded mucoperiosteum. The use of aqueous

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formulations of nonototoxic topical antibiotics, steroids, or antifungals placed on the mucoperiosteum hastens recovery from otitis media. Topical levels of these drugs may be many times the level that can be achieved using parenteral therapy, even when there is severe hyperemia of the mucoperiosteum. Antibiotic concentrations are high in inflamed tissues, because the increased blood flow allows increased serum levels of antibiotic to perfuse the inflamed tissue. Even these levels may not achieve the minimum inhibitory concentration (MIC) necessary to kill the bacterial target, however. Infusing drugs into the bulla is an effective method of providing long-acting high-concentration effects. The tympanic bulla in the dog and cat is a deep blind pouch. When the bulla is filled with antibiotic, the fluid cannot escape easily. Most of the topical antibiotic solution can remain within the bulla for several days after infusion. During the first bulla infusion, less than 1 mL of solution can be infused into the inflamed bulla. The entire procedure of flushing, suctioning, and bulla infusion should be repeated weekly during therapy. With each successive treatment, the mucoperiosteum should retract slightly, increasing the volume of fluid the bulla can accommodate.

Reduce inflammation with corticosteroids Corticosteroids slow the intense inflammation and exudation found in middle ear disease. As described earlier, the mucoperiosteum undergoes severe pathologic changes in response to inflammation. Corticosteroids can reverse some of the extensive granulation that forms in the bulla, which enhances the ability of topically applied antibiotics to penetrate into the infected tissue. The tympanic cavity is crowded out by this hyperemia and proliferating granulation tissue; thus, the amount of free space within the bulla decreases. Reducing the inflammation helps this lining membrane to retract back toward the bone, increasing the volume within the bulla. When the eardrum heals, this space should refill with air. Corticosteroids also reduce the amount of mucus produced in the bulla and decrease the viscosity of the secretions from the inflamed mucous membrane in the bulla. Changing the character of the mucus aids in its removal. Corticosteroids may also function in reducing the swelling in the auditory tube, increasing lumen diameter, which has the beneficial effect of offering limited drainage of mucus into the nasopharynx. Aqueous topical corticosteroids, such as dexamethasone sodium phosphate (4 mg/mL) or a dimethyl sulfoxide (DMSO)/cortisone combination may be infused through a catheter placed into the cleaned and dried bulla. These potent topical anti-inflammatories are not ototoxic. Other potent injectable topical corticosteroids are formulated with ototoxins, such as benzyl alcohol or propylene glycol, or they are in suspension. These should not be used in the bulla. If there is bacterial or fungal disease and the space in the bulla is needed for antibiotic or antifungal topical therapy, systemic corticosteroids may be used for a few weeks during the recovery phase of otitis media. High initial doses of corticosteroid are required, which mirror those used for other diseases, such as inflammatory bowel disease. Patients should be screened for diabetes, hyperadrenocorticism, demodicosis, and potential pregnancy before using the high doses of corticosteroids. Prednisone or prednisolone, 2 to 4 mg/kg daily for 2 weeks and then decreasing to 1 mg/kg every other day, provides high enough levels to decrease inflammation within the bulla. Owners of these animals need to be warned that there will be side effects of prednisone at this high dose. Many owners discontinue the medication when the side effects occur. It may be preferential to use a 0.2-mg/kg intravenous dose of dexamethasone (2 mg/mL) at the time of treatment and then to repeat this injection weekly at the recheck appointment if there is significant exudate that needs to be suctioned from the bulla. This has fewer mineralocorticoid-related side effects and prevents the owners from having the choice of stopping the medication.

Systemic and topical antimicrobials The dilemma facing the clinician treating otitis media is that systemic drug levels may not reach sufficient MIC in the bulla and topical treatment requires frequent applications. Using maximal doses of oral antibiotics along with weekly bulla infusions of a fresh supply of antibiotic increases the therapeutic successes. Topical antibiotic treatment of otitis media has gained recent favour in veterinary medicine. The use of topicals is based on the high levels of antibiotic that can be placed into the bulla coupled with the poor drainage of the tympanic bulla. Aqueous solutions of nonototoxic antibiotics can be placed directly onto the infected mucoperiosteum. Infused

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antibiotics can remain in contact with the inflamed granulating middle ear mucosa much longer, because the fluid filling the bulla cannot readily escape. When topical therapy of otitis media fails, it is usually the result of inability of the antibiotic to get to the bacteria. For example, there may be sequestration of bacteria within folds or pockets of granulation tissue unexposed to the topical antibiotic. Antibiotic sensitivity patterns are important for treating otitis media when systemic antibiotics alone are used to get levels within the bulla. Unlike topical antibiotics, which can achieve many times the blood MIC, systemic antibacterial therapy for otitis media relies on lower levels of antibiotics arriving in the middle ear hematogenously or through inflammatory cells. Because of the poor blood supply in the external ear canal and middle ear, there is limited diffusion of antibiotic from the serum into the lumen of the ear canal or tympanic bulla. The choice of antimicrobial agents becomes more complicated when otitis media is involved. It is preferred to avoid the topical use of fluoroquinolones completely unless a systemic form of the same drug is used concurrently because of the potential for sub-therapeutic concentrations of the topical drug to reach the middle ear via the ruptured tympanum. Development of fluoroquinolone resistance is documented to occur in vitro with a single exposure to the drug. Many veterinary dermatologists recommend starting an oral fluoroquinolone pending culture/susceptibility results. Systemic antimicrobial therapy based on culture/susceptibility testing of samples retrieved from the middle ear is indicated whenever possible. In fact, it has been stated that otitis media cannot be resolved with topical therapy alone. Many chronic cases of otitis media involve P aeruginosa, however, and an oral drug is not always available because of broad-spectrum resistance. Several systemic antipseudomonal drugs intended for intravenous use can also be used subcutaneously, allowing therapy by the client at home. Examples include meropenem (8 mg/kg every 12 hours), ticarcillin (40–80 mg/kg every 6 hours), and ceftazidime (30 mg/kg every 4 hours). The downfall of these systemic injectable drugs is their extremely high cost. In cases of Pseudomonas otitis media in which an oral antibiotic is unavailable and the cost of subcutaneous therapy is prohibitive to the client, success with thorough bulla lavage followed by high-throughput topical therapy has been shown. The later entails application of large volumes (1–2 mL) of topical drug (most often, an SSD solution) twice daily and regular (daily or every other day) at-home flushing of the canals using a cleanser (Epiotic Advanced, Virbac). It is our contention that high-volume application of low-viscosity antimicrobial preparations and cleansers promotes a continued ‘‘flushing’’ of the bullae as long as the tympani remain open. Methicillin-resistant Staphylococcus spp also present a dilemma in selecting a systemic antibiotic. Methicillin resistance (indicated by resistance to oxacillin in most susceptibility profiles) confers resistance to all β-lactam antibiotics, and many of these strains also show broad fluoroquinolone resistance patterns. Most strains isolated from patients presenting to the dermatology service at the University of Pennsylvania have been susceptible to chloramphenicol or macrolide antibiotics (erythromycin, azithromycin, and clarithromycin).The methicillin resistance status in South African companion animal practice is unknown at this stage although methicillin resistant Staphylococcus spp. have been isolated from dermatology cases at the Onderstepoort Veterinary Academic Hospital. Regardless, the successful therapy of bacterial or fungal otitis media relies on an initial thorough cleansing of the bulla, aggressive targeted antimicrobial therapy for an absolute minimum of 6 to 8 weeks, and consistent cleansing/flushing of the external canal by the client at home. Therapy can only be discontinued when the ear canals are negative for microorganisms on cytologic examination, the external canals have no residual oedema, and the epithelium has normalized. In some cases, the tympanic membrane may not regenerate, although most do. In cases in which these criteria cannot be achieved, a prophylaxis program that incorporates regular use of cleansers must be instituted. The level of commitment on the part of the client cannot be overly stressed. In one report, the mean time to resolution of chronic otitis media in 44 dogs was 117 +- 86.7 days (range: 30-360 days)

Rechecks With successive recheck visits, the eardrum and the horizontal canal should be examined for fluid, mucus, and pus. If there is fluid within the bulla, it should be flushed out and the bulla suctioned to prepare it for re-infusion. When the weekly examination reveals a dry canal and little liquid within the bulla, the inflammation and infection within the bulla have subsided. At this point, bulla infusion treatments can be discontinued. Subsequent 2-week recheck intervals should reveal a healing eardrum.

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Chronic otitis externa References. Numerous references have been used to collate these notes. Some of the most useful are 1-13 1. Matousek JL. Ear disease. The Veterinary clinics of North America Small animal practice 2004;34:XI-XII. 2. Lanz OI, Wood BC. Surgery of the ear and pinna. The Veterinary clinics of North America Small animal practice 2004;34:567-599, viii. 3. Gortel K. Otic flushing. The Veterinary clinics of North America Small animal practice 2004;34:557-565. 4. Morris DO. Medical therapy of otitis externa and otitis media. The Veterinary clinics of North America Small animal practice 2004;34:541-555, vii-viii. 5. Matousek JL. Diseases of the ear pinna. The Veterinary clinics of North America Small animal practice 2004;34:511-540. 6. Fan TM, de Lorimier LP. Inflammatory polyps and aural neoplasia. The Veterinary clinics of North America Small animal practice 2004;34:489-509. 7. Gotthelf LN. Diagnosis and treatment of otitis media in dogs and cats. The Veterinary clinics of North America Small animal practice 2004;34:469-487. 8. Rosser EJ, Jr. Causes of otitis externa. The Veterinary clinics of North America Small animal practice 2004;34:459-468. 9. Bischoff MG, Kneller SK. Diagnostic imaging of the canine and feline ear. The Veterinary clinics of North America Small animal practice 2004;34:437-458. 10. Cook LB. Neurologic evaluation of the ear. The Veterinary clinics of North America Small animal practice 2004;34:425-435, vi. 11. Angus JC. Otic cytology in health and disease. The Veterinary clinics of North America Small animal practice 2004;34:411-424. 12. Cole LK. Otoscopic evaluation of the ear canal. The Veterinary clinics of North America Small animal practice 2004;34:397-410. 13. Heine PA. Anatomy of the ear. The Veterinary clinics of North America Small animal practice 2004;34:379-395.

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SAVA KZN Branch Meeting San Lameer

21-22 May 2016

Petrie VogelTel: 012 346 0687Fax: 012 346 [email protected]

Canine Prostatic Disease Dr Daniela Steckler

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