I REGIONAL VETERINARY LABORATORIES REPORT Regional ... · Veterinary Ireland Journal I Volume 9...

33Veterinary Ireland Journal I Volume 9 Number 1

LIVER FLUKE FORECAST FOR WINTER 2018/2019The DAFM has issued a liver fluke forecast for winter 2018/2019, which reflects the probability of exposure of livestock to liver fluke based on meteorological data. Due to the dry weather conditions experienced in many parts of the country this summer, there is a moderate risk of liver fluke-related disease this winter for the north, west, southwest and midlands, with a lower disease risk expected for the east and parts of the south. However, farmers in these lower-risk areas should still remain vigilant for signs of disease. The forecast’s predictions on the risk in di�erent geographical areas are consistent with information on the liver fluke status of animals from various sources including:• Testing blood samples taken by DAFM RVL sta� from

slaughtered lambs during the summer and autumn of 2018; and

• Post-mortem examination of bovine livers by vets, reflected in Animal Health Ireland’s Beef Health check data.

For further information please refer to: www.agriculture.gov.ie/press/pressreleases/2018/november/title,122100

CATTLEThe gastrointestinal tract was the most commonly identified organ system a�ected in bovine carcases (excluding foetuses), which were received by to the RVLs in October 2018. The cause of death was located in this organ system in 29.6% of the submitted bovine cases.

GASTROINTESTINAL TRACTParasitic gastroenteritisA seven-month-old weanling was submitted to Limerick RVL with a history of diarrhoea for two weeks. Necropsy revealed

very poor body condition. Intestinal contents were liquid. Scraping of the surface revealed trichostrongyle larvae in large numbers on the mucosa. A trichostrongyle egg count of 2,500eggs per gram (epg) was detected in this animal, confirming the diagnosis of parasitic gastroenteritis.Limerick RVL received a 5.5-month-old weanling calf with a history of poor thrive and diarrhoea in the management group. The farmer reported 10 previous deaths of which some had been previously submitted to Limerick RVL. The history stated that the calves were dosed regularly. On post-mortem examination, the abomasal mucosa had a nodular haemorrhagic appearance, also described as ‘Moroccan leather’, suggestive of a severe parasitic infection (Figure 1) and the intestinal contents were very watery in consistency. Faecal parasitology results were negative suggesting that this was an acute pre-patent infection.

In autumn 2018, a number of weanling calves had been seen with acute stomach worm infection at post mortem in Limerick RVL, despite low or even negative faecal egg counts. A�ected calves had severe gross signs at necropsy with worms visible in the mucosa upon histopathology (Figures 2 and 3). It is possible that dry weather earlier this summer followed by heavy autumn rainfall has led to a syndrome of acute parasitic gastroenteritis following a delay in the worm-egg hatch.

Regional Veterinary Laboratories Report

Regional Veterinary Laboratories (RVLs) carried out necropsy examinations on 455 carcases and 121 foetuses during October 2018. There were 2,586 diagnostic samples submitted to RVLs in addition to carcases referred by private veterinary practitioners (PVP) for assistance in the diagnosis and disease control in food-producing animals. This report describes a selection of cases investigated by the Department of Agriculture, Food and the Marine’s (DAFM)

RVL network in the previous months. The application of specialist knowledge, experience and technical abilities by RVL sta� investigating disease on Irish farms is crucial in maintaining disease surveillance and protecting the health and international reputation of the Irish livestock industry. Veterinary practitioners are reminded to contact their local RVL to receive advice and support when unidentified disease outbreaks are encountered in all farmed species.

Table 1: Breakdown of gastrointestinal diagnoses in bovine carcases (excl. foetuses) in October 2018.

0% 10% 20% 30% 40%

Parasitic gastroenteritis

Enteritis

Gastroenteritis

Abomasal Ulcer/Perf/Peritonitis

Intestinal torsion

Intususception

Gastric ulcer

Bloat

I REGIONAL VETERINARY LABORATORIES REPORT

Figure 1: ‘Moroccan leather’ appearance of the abomasal mucosa in an animal with acute pre-patent parasitic gastritis. Photo: William Fitzgerald.

October 2018

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Veterinary Ireland Journal I Volume 9 Number 1

MALOCCLUSIONSligo RVL received an 18-month-old bullock for post-mortem examination that had been reported as pining away. A state of emaciation was noted during post-mortem examination. A thorough exam of the oral cavity revealed a bilateral irregular molar wear resulting in an exaggerated step mouth. There was concurrent chronic-active parasitic hepatitis, typical of Fasciola hepatica infection. The molar misalignment was deemed to be the primary cause of the malnutrition, however parasitism is likely to have contributed to the decline in body condition. The cause of the irregular molar wear could not be elucidated.

RUMINAL ACIDOSISA two-year-old cow was submitted with history of sudden death. Ruminal contents were grossly dark in colour and were shown to be markedly acidic, zero motility of rumen fauna was observed on microscopy. Gross lesions of mastitis were judged to be an incidental finding and a diagnosis was made of ruminal acidosis. The submitting vet undertook a review of feeding.

RESPIRATORY TRACTLaryngitisAn eight-month-old Friesian heifer was submitted to Kilkenny RVL with a history of sudden death. On post-mortem examination, the liver was very large with multifocal abscesses throughout. There was a severe necrotic laryngitis. Trueperella pyogenes and Pasteurella multocida were cultured from the larynx. Bacteraemia and septicaemia are the most likely cause of death. Which of these described lesions was the primary one could not be fully elucidated.

PNEUMONIAA 10-month-old bullock was presented to Limerick RVL with a history of sudden death. Necropsy revealed marked changes within the lungs. There were pleural adhesions, severe interstitial change seen bilaterally and localised areas of ‘ground-glass’ emphysema. Within the airways there was haemorrhagic exudate. The lungs contained numerous bullae. Laboratory findings revealed Mannheimia haemolytica, Pasteurella multocida and Respiratory Syncytial Virus (RSV) detected by polymerase chain reaction (PCR). Bacterial pneumonia was ruled to be the most likely cause of death.

URINARY/REPRODUCTIVE TRACTGlomerulonephritisLimerick RVL diagnosed chronic glomerulonephritis and uraemic encephalopathy on histopathology of brain and kidney samples from a seven-year-old Friesian cow with a history of chronic diarrhoea, weight loss and poor milk production over a two-month period. On necropsy, both

Figure 2: Multiple nematodes in the abomasal mucosa of a weanling calf. Photo: Ian Hogan.

Figure 3: Nematodes in the abomasal mucosa of a weanling calf. Photo Ian Hogan.

Figure 4: Necrotising laryngitis in a heifer. Photo: Aideen Kennedy.

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REGIONAL VETERINARY LABORATORIES REPORT I


kidneys appeared pale, mottled, enlarged and with an adherent renal capsule indicating chronic kidney disease. No significant bacterial pathogens were isolated but this is not unusual given the chronic course.

PYELONEPHRITISA six-year-old cow was submitted to Sligo RVL for post-mortem examination. She had presented with unspecific signs in the days prior to death and died despite treatment after an initial improvement. Both kidneys were severely enlarged on post mortem examination and there was multifocal necrosis in renal lobules (ie. some of the tissue in each renal lobule was necrotic, see Figure 5). There was a large amount of purulent fluid present in the renal pelvis and severe haemorrhage beneath the renal capsule on both kidneys. Trueperella pyogenes was cultured from kidney tissue. Urea values were significantly raised in vitreous humour. Pyelonephritis caused by Trueperella pyogenes was the most likely cause of death in this case.

A further case of pyelonephritis occurred in a 30-month-old bullock submitted to Sligo RVL for post mortem examination. The animal had presented with sti�ness and pain, restlessness, sweating and haematuria. He died despite treatment e�orts. On necropsy, the kidneys were severely enlarged with a fluid-filled capsule. There were white ‘pinprick’ multifocal areas throughout the renal parenchyma. There was multifocal mildly-haemorrhagic ulcerative abomasitis. Severe multifocal, acute, purulent, necrotising nephritis was diagnosed on histopathology (Figure 6). No pathogen could be detected by culture or PCR. In many cases, culture is unsuccessful after antimicrobial treatment as the pathogens are weakened and growth can be inhibited.

CARDIOVASCULAR SYSTEMBovine neonatal pancytopaeniaA 17-day-old suckler calf was submitted to Kilkenny RVL with a history of pneumonia. The animal had been treated with antibiotics and the farmer noted bleeding from the injection sites. Necropsy findings included haemorrhagic areas over the gluteal muscles with necrotic muscle where the calf had been injected. The carcase was pale. The umbilical arteries had very large blood clots. The thymus, spleen, kidneys and intestines had multiple pinpoint haemorrhages. A number of lymph nodes were enlarged. Bone marrow showed trilineage hypoplasia consistent with bovine neonatal pancytopaenia on histopathology.

NERVOUS SYSTEMMalignant peripheral nerve sheath tumourCork RVL received samples of mediastinal lymph nodes from a cow, which presented with dyspnoea wasting and large growths in her mediastinum and neck area. Histological examination of the sections revealed a mass formed by densely infiltrative sheets of tight, interlacing bundles of spindle-shaped cells (Figure 7). The cells were pleomorphic with indistinct cell borders, oval nuclei and evident nucleoli. Numerous mitotic figures were noticed (12 per high power field [40x]), many of them aberrant. There were also multiple areas of necrosis and at the periphery, clusters of lymphocytes, plasma cells and haemosiderin. The appearance of the mass suggested a nerve sheath tumour arising from di�erentiated Schwann cells (Schwannoma). This type of tumour is usually benign. In cattle, this neoplasm often involves the brachial plexus and intercostal nerves but occasionally the autonomic nerves of the liver, the epicardial plexus, mediastinum and thorax can be a�ected. In this case, the presence of multiple areas of necrosis, the anaplastic appearance of the neoplastic cells and the high rate of mitosis were indicative of malignancy.

Figure 5: Kidney from a cow with necrotising (arrow head) pyelonephritis. Photo: Rebecca Froehlich-Kelly.

Figure 6: Photomicrograph of purulent exudate in a section of kidney from a bullock with severe multifocal, acute, purulent, necrotising nephritis. Photo: Rebecca Froehlich-Kelly.

Figure 7: Photomicrograph depicting sheets of tight interlacing bundles of spindle-shaped cells in a nerve-sheath tumour found in the mediastinum of a cow with dyspnoea. Photo: Cosme Sánchez-Miguel.

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MUSCULOSKELETALRound cell tumourAn 18-month-old Friesian heifer was submitted to Athlone RVL for post mortem examination. The farmer had noticed swollen areas on the hindquarters/limbs since April, there had been no response to treatment and the animal was euthanased. There was a discharging cutaneous lesion on the right hip, with subcutaneous swelling extending down the right hind limb. On incision, multifocal areas of cream, firm, lymphoid-type tissue extended from the subcutaneous areas through the muscle layers (Figure 8). There was also a raised circular 10cm diameter lesion on the right shoulder and on incision there was another similar firm cream-coloured lesion suggestive of lymphoid tissue (Figure 9). Trueperella pyogenes was isolated from the wound on the right hip indicating a secondary infection following skin ulceration. A diagnosis of a round cell tumour was made on histopathology of the mass, and further analyses to determine the cell type are ongoing.

POISONINGS/MISCELLANEOUSBotulismAn eight-month-old weanling was submitted to Kilkenny RVL with a history of being sti�, prior to recumbency. The animal died despite treatment. On post mortem, the rumen contained chicken bones and wings, numerous vegetables, twine, and what appeared to be a plastic rubbish bag indicating the animal had ingested waste material including a poultry carcase. Samples of the rumen, abomasum, small intestine and large intestine content were collected for botulinum toxin ELISA and yielded a positive result. It was thought that the likely source of the botulism toxin was the waste material as poultry carcases and poultry waste products are considered potential sources of botulism toxins. This case highlights the importance of regular examination of fields to prevent exposure of animals to any dumped material.

SHEEPThe respiratory tract was a�ected in sheep carcases in 13.8% of submissions (excl. foetuses)

RESPIRATORY TRACTPneumoniaA two-year-old ewe was delivered to Sligo RVL for necropsy with a history of failing for the previous two weeks. The carcase was emaciated and the lung presented with multifocal abscessation and focal pleurisy. Intestinal contents were green and mildly haemorrhagic. Bibersteinia trehalosi, Pasteurella multocida and Escherichia fergusoni were detected by PCR and

Figure 8: Neoplastic mass in muscle tissue in a Friesian heifer. Photo: Denise Murphy.

Figure 10: Chicken bones recovered from the rumen of a weanling with the diagnosis of botulism. Photo: Aideen Kennedy.

Figure 9: A neoplastic mass identified as being of round cell origin in the subcutaneous tissue of a Friesian heifer. Photo: Denise Murphy.

Table 2: Breakdown of diagnoses in the respiratory tract in sheep carcases (excl. foetuses) submitted in October 2018.

0% 20% 40% 60%

Pneumonia

Ovine pulmonary adenocarcinoma/Jaagsiekte

Pneumonia and septicaemia

Pleuropneumonia

Laryngeal chondritis

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cultured from lung tissue. There were also severely elevated faecal worm egg counts for trichostrongyles and Nematodirus sp. Polymicrobial pneumonia and parasitic gastroenteritis were deemed the most likely cause of death in this case. Although parasitic worm egg counts can be elevated in weak or moribund animals and might not be reflective of the wider flock or herd status, investigation of the parasitic burden in flock/herd comrades is indicated in such cases.

PasteurellosisThree lambs, approximately six months of age, were submitted to Athlone RVL for post-mortem examination. The farmer had lost 14 lambs in the previous two days and the animals were found dead without signs, or recumbent, drooling, and becoming profoundly depressed, followed by death. On post-mortem examination there was ulceration of the tongue and pharynx with a fibrin coating of the oesophagus (Figure 11). The lungs were haemorrhagic. Bibersteinia trehalosi was cultured from multiple organs. A diagnosis of systemic pasteurellosis was reached.

MUSCULO-SKELETALSligo RVL received a one-year-old ewe and an eight-month-old ram for post-mortem examination, which showed swelling around the front legs and drowsiness approximately one week after being vaccinated. Both animals presented with extensive oedema and necrotising, gangrenous myositis around the front leg and ventral neck area. Trueperella pyogenes was isolated from the a�ected areas. Histopathology revealed severe, focally extensive, acute, suppurative, necrotising myositis with macrophages and lymphocytes present, as well as extensive oedema and large amounts of bacterial colonies. In the ram there was an incidental finding of a large number of protozoal cysts present in the skeletal muscle without an appreciable inflammatory reaction. The most likely parasite causing these is Sarcocystis spp.. Cause of death in this case was most likely the gangrenous myositis and septicaemia. However, in this case an improvement of biosecurity on feed stores was recommended to prevent feed contamination with Sarcocystis spp. or other parasites by dog and cat faeces.

OSTEOCHONDROSISAn eight-month-old purebred Texel ram lamb was submitted for necropsy to Athlone RVL with a history of sti�ness and incoordination. On gross examination, there were erosions of the articular cartilage surface of the elbow joints bilaterally and to a lesser extent, in the hocks with excess, clear joint fluid. There were no significant gross findings in the neck, carcase musculature and brain. Histopathology findings in the bone suggested a chronic injury and a subsequent repair response. Osteochondrosis (OCD) dissecans and subsequent chronic fibrosis was a possible di�erential diagnosis. However, characteristic clefts or islands of necrotic articular cartilage due to vascular compromise seen in OCD could not be confirmed histologically in the tissue supplied. This might be due to the chronic duration.Interpretation of the histological findings were considered together with gross appearance of the lesions where an articular cartilage defect had to be di�erentiated from synovial fossae which together with absence of an inflammatory arthritis, were considered suggestive of OCD dissecans. There is no single cause of OCD but several contributing factors have been identified which include genetic predisposition, physical activity and rapid growth rate (Figure 13) and cultured from lung tissue.

Figure 11: Diphtheritic membrane in the pharynx of a lamb with systemic pasteurellosis. Photo: Seamus Fagan.

Figure 12: Sarcocystis cysts in the skeletal muscle of a sheep that are considered an incidental finding. Photo: Rebecca Froehlich-Kelly.

Sheep are common intermediate hosts for Sarcocystis tenella (synonym: S. Ovicanis; final host dog) and Sarcocystis gigantea (synonym: S Ovifelis; final host cat). Almost all findings of Sarcocystis spp. cysts in muscles are an incidental finding without evidence of adverse e�ects. However, clinical disease can occur in the intermediate host (sheep in this case). Sarcocystis spp. can be very virulent in lambs at high infective doses and it has been associated with encephalomyelitis in older sheep. Large number of muscle cysts can lead to poor muscle performance and chronic debilitation. The cysts are commonly found in skeletal, heart and oesophageal muscle.

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POISONINGSCopper toxicityA 17-month-old ram was submitted to Kilkenny RVL. The ram had died following being unresponsive to antibiotic therapy. On post-mortem examination, the carcase was jaundiced. The kidneys appeared black in colour and the urine was dark. Laboratory testing indicated both liver and kidney copper concentrations were above the reference range. Histological examination revealed deposition of pigmented material in renal tubules and tubulorrhectic acute tubular injury consistent with haemoglobinuria and copper toxicity. Additional laboratory findings included a trichostrongyle count of 1,750 epg.

PIGS

RESPIRATORY TRACTPleuropneumonia and pericarditisPathology division investigated a rapid increase in mortality in a large commercial pig herd. Late-stage weaners and early-stage fatteners were reported as dying following an acute respiratory illness. Marked reddening of ventral body areas was reported as a consistent clinical sign and the farmer reported that one to

two pigs were being found dead or dying each morning from a�ected batches. Six pigs were submitted for necropsy which yielded similar findings in all pigs examined. There was severe di�use fibrinous pleuritis and pericarditis with large amounts of fresh fibrin deposited on thoracic serosal surfaces. Excess blood-stained fibrinous thoracic fluid was present. Fibrous adhesions were not detected in pleural or pericardial cavity indicating a rapid onset. Pulmonary lesions were considered extremely severe with di�use consolidation of 80-90% of lung parenchyma in all pigs. There was marked necrosis of the parenchyma in diaphragmatic lobes in all pigs. There was mild excess of abdominal fluid and small amounts of fibrin in some pigs. Distribution and severity of lesions were consistent with Actinobacillus pleuropneumonia (APP) infection which was later confirmed by culture and histopathology.

OTHER SPECIES

POULTRYAvian tuberculosisPoultry submissions from backyard flocks are always encouraged as part of our passive surveillance for Avian Influenza. On this occasion, a couple of hens, from a flock of 18, died after an episode of diarrhoea and convulsions. On post-mortem examination, both hens were very emaciated and showed similar gross lesions. The liver, spleen and lungs presented with multifocal white granulomas (Figure 15). Those lesions were strongly indicative of avian tuberculosis and as expected routine cultures were unremarkable. Histological examination of sections with a Ziehl-Neelsen stain confirmed the presence of acid-fast bacilli within the granulomas consistent with avian tuberculosis (Figure 16).

Figure 13: Articular cartilage defect (arrow head) in the femoro-tibial joint of a ram lamb. Photo: Denise Murphy.

Figure 14: Gun-metal coloured kidneys in a case of copper poisoning in a ram. Photo: Aideen Kennedy.

APP is a relatively commonly diagnosed cause of pneumonia in pigs. Severe outbreaks may occur in naive populations causing a rapidly fatal pleuropneumonia. The source of infection is likely to be previously infected pigs where the organism remains as a sequestra in pulmonary parenchyma or in tonsils and nasal cavity. There are marked di�erences in virulence of strains and the disease is di�icult to eradicate from herds. The severity of the disease is dependent both on the virulence of the train and the infectious dose. In experimental conditions death has occurred as rapidly as three hours post inoculation.

Though the Mycobacterium avium bacillus has been isolated in a few instances in humans, cases of this infection in man are extremely rare and poultry are of little importance in the epidemiology of human tuberculosis. Nevertheless, carcases of tuberculous poultry are not suitable for human consumption and destruction of this flock was advised.

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Figure 15: Random multifocal pale white-to-yellow granulomas (avian tuberculosis) in the liver of a hen.Photo: Cosme Sánchez-Miguel.

Figure 16: Microphotograph demonstrating round to oval nodules (granulomas) with a central core of necrosis and surrounded by inflammatory cells (arrows). Inset: Ziehl–Neelsen stained acid-fast bacilli (fuchsia) in the necrotic core. Photo: Cosme Sánchez-Miguel.

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