Modern Parasitology For The Cat - Zoetis | zoetisUS.com · 4 | McKay et. al., 2013. Journal of...

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Modern Parasitology For The Cat: Fleas, Mites, and Worms, Oh My!

Annette Litster BVSc PhD FACVSc (Feline Medicine) MMedSci (Clinical Epidemiology) Senior Veterinary Specialist, Zoetis

Chris Adolph DVM, MS, DACVM (Parasitology) Veterinary Specialist, Zoetis

Document No. TI-02839 All trademarks are the property of Zoetis Services LLC or a related

company or a licensor unless otherwise noted.

© 2017 Zoetis Services LLC. All rights reserved.

RISK FACTORS AND LIFE CYCLE

FELINE HEARTWORM INFECTION

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McKay et. al., 2013. Journal of Medical Entomology 50 (4): 871-878.

Ledesma, N., and L. Harrington, 2015. Veterinary Parasitology 209(1-2):93-100.

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McKay et. al., 2013. Journal of Medical Entomology 50 (4): 871-878.

Ledesma, N., and L. Harrington, 2015. Veterinary Parasitology 209(1-2):93-100.

A single heartworm-positive dog potentially increases infection pressure on susceptible

animals sharing mosquito exposure

At colder temperatures, average daily temperature models underestimate L3 development; modeling hourly

temperature more accurately predicted D. immitis development to infective L3’s. (Ledesma and Harrington, 2015)

Environmental Risk NE AK – Frequency of D. immitis-infected Mosquitoes

SHELTER + 5 RESIDENTIAL AREAS

INSIDE KENNEL OF 1 HW-INFECTED DOG

7.3% 73.7% 10X

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LIFE CYCLE OF DIROFILARIA IMMITIS IN THE CAT

Microfilaria

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L1

L2 L3


Microfilaria

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L1

L2 L3


Microfilaria

6 months X

Immature Adult

L3

L4 Adults

MF (L1)

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6 months

Mosquito infects

cat with L3 Stages Susceptible

to Preventatives

X

L1

L2 L3

L3 L4 Immature Adult

0 30 60 90 120 150 180

D A Y S

Adult

210 240


Microfilaria

Immature Adult

L3

L4 Adults

MF (L1)

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CATS INSIST ON BEING DIFFERENT

CLINICAL SIGNS

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Cats more resistant to infection

True prevalence?

Mosquito vectors

Worm burden

High larval mortality rate

Microfilaremia – Host suppression and clearance

Aberrant larval migration

Reduced lifespan

HEARTWORM DISEASE FELINE VS. CANINE1

1. Litster and Atwell, 2008. Journal of Feline Medicine and Surgery 10:137-144.

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Larval arrival into pulmonary vasculature

– Antibody–mediated response

– Pulmonary arteritis

– HARD

Death of adult worms – Acute death syndrome

CLINICAL SIGNS ASSOCIATED WITH IMMUNE RESPONSE TO

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0 3 6 9-24 mos

Months after Infection

Ab

Ag ?

Microfilariae?

FELINE HEARTWORM DISEASE: CLINICAL TIMELINE

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HARD

0 3 6 9-24 mos

Eosinophilia

Adult HW- PA Lesion Cat +/- Clinical Signs

Bronchitis


Ab

Ag ?

Microfilariae?


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HARD

0 3 6 9-24 mos

Eosinophilia

Adult HW- PA Lesion Cat +/- Clinical Signs

Bronchitis


Ab

Ag ?

Microfilariae?


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BLAGBURN & DILLON HARDs STUDY1

1. Blagburn BL, Dillon AR. Feline heartworm disease: solving the puzzle. Veterinary Medicine (supplement) 2007; March: 7-14.

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EVEN CATS WITH HEARTWORM INFECTION THAT NEVER DEVELOPED ADULT WORMS INCURRED SIGNIFICANT BRONCHIAL AND PARENCHYMAL DISEASE

THE ACUTE DEATH SYNDROME IN FELINE HEARTWORM DISEASE


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Prevalence – Unknown but estimates range from 10% to 47% of infected cats

Clinical presentations

Necropsy findings

Hypotheses –

– Acute pulmonary thromboembolism associated with death of adult filariae (Dillon 1998)

– Acute systemic anaphylaxis (Brown et al 1999) – worm breakage during extraction procedures

– Role of Wolbachia?

THE ACUTE DEATH SYNDROME1

1. Litster et al., 2008. Veterinary Parasitology 158:196-203.

DIAGNOSIS


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FELINE HEARTWORM DIAGNOSIS

(Ab- & Ag-)

Preventative

ANTIBODY AND ANTIGEN TEST

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(Ab- & Ag-)

Preventative


L4-Early Adult infection/ Previous Adult infection

Preventative Discuss Potential Complications

+/- Thoracic radiographs +/- Echocardiography +/- Angiography

(Ab+ & Ag-)

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(Ab- & Ag-)

Preventative




Positive HW Diagnosis


(Ab+ & Ag-)

No Approved or Recommended

Treatment

Supportive Care and

Preventative

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(Ab- & Ag-)

Preventative




Positive HW Diagnosis

(Ab+ & Ag+)


(Ab+ & Ag-)

No Approved or Recommended

Treatment

Supportive Care and

Preventative

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Antigen-antibody complexes interfere with antigen detection

Heat treatment at 103°C for 10 minutes breaks up complexes

Six HW-infected cats with low worm burdens Before heat treatment – 0/6 specimens Ag+ After heat treatment – 5/6 specimens Ag+

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TOTAL # CATS

# POSITIVE BEFORE HEAT TREATMENT

# POSITIVE AFTER HEAT TREATMENT

Shelter cats 220 1 13 (6%)

Free-roaming cats 165 4 13 (8%)

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TOTAL # CATS

# POSITIVE BEFORE HEAT TREATMENT

# POSITIVE AFTER HEAT TREATMENT

Shelter cats 220 1 13 (6%)

Free-roaming cats 165 4 13 (8%)

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Photo: Dr. S. Foster

Rib 9

Right

PA Left

PA

FELINE HEARTWORM

INFECTION VD VIEW

TREATMENT


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1. American Heartworm Society Current Feline Guidelines 2014 http://www.heartwormsociety.org/

FELINE HEARTWORM DISEASE –TREATMENT1

Wait for self-cure?

6-12 monthly monitoring

– Ag + Ab testing, thoracic radiographs

– Most cats become Ag negative 4-5 months after infection clears – good prognostic sign

– Timing to Ab negative state indeterminate (months-years)

– Seroconversion to negative, regression of radiographic signs indicate risk period has probably passed

ASYMPTOMATIC CATS

http://www.heartwormsociety.org/

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Prednisolone in diminishing doses – 2mg/kg q24h declining to 0.5mg/kg q48h over 2 wks, discontinue after a further 2 wks

Reassessment after prednisolone based on clinical response and radiographic signs

Repeat if clinical signs recur

Regular monitoring important

Aspirin and NSAIDs – Failed to produce benefits – may exacerbate pulmonary parenchymal disease

CATS WITH EVIDENCE OF RADIOGRAPHIC DISEASE


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1. American Heartworm Society Current Feline Guidelines 2014 https://www.heartwormsociety.org/images/pdf/2014_AHS_Feline_Guidelines.pdf (Accessed August 15 2017)

2. Dhupa 2005 http://www.ivis.org/proceedings/navc/2005/SAE/060.pdf?LA=1 (Accessed August 15 2017)

FELINE HEARTWORM DISEASE – TREATMENT1, 2

O2 via nasal catheter/airway

Epinephrine – 0.01mg/kg 1:1000 solution IM, SC, sublingually

Isotonic crystalloid fluid bolus (45-60 mL/kg)

Antihistamines e.g. Diphenhydramine 0.5-2.0 mg/kg IM q8h

High-dose IV glucocorticoids after circulatory collapse is reversed

Bronchodilators e.g. Terbutaline 0.01 mg/kg SC

Diuretics inappropriate

Anti-serotonin drugs – Cyproheptadine?

ACUTELY ILL CATS

https://www.heartwormsociety.org/images/pdf/2014_AHS_Feline_Guidelines.pdf

https://www.heartwormsociety.org/images/pdf/2014_AHS_Feline_Guidelines.pdf

http://www.ivis.org/proceedings/navc/2005/SAE/060.pdf?LA=1

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Intravenous

Basket Catheter

Accidental Worm Transection → Acute Death

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Physical obstruction by worm burden not a problem for most cats

‘Anaphylactic’ reaction on worm death fatal

ADULTICIDAL THERAPY

Toxic to cats in doses as low as 3.5mg/kg

Use in cats is not approved

MELARSOMINE


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Given over 2 years reduces worm burden

Slow kill thought to reduce chances of acute reaction

Might be used in combination with 30 day course of doxycycline to increase effectiveness of adulticidal action

Use of macrocyclic lactones for treatment of heartworm disease in cats is not approved.

SELAMECTIN/MOXIDECTIN/IVERMECTIN AS ADULTICIDES

While there is no published evidence that any form of adulticide therapy increases survival in HW-infected cats, the Blagburn and Dillon studies demonstrated that monthly selamectin will prevent further infections and HARDs

BOTTOM LINE – PREVENTION SHOULD BE PRIORITIZED


PROPHYLAXIS


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FELINE HEARTWORM DISEASE – PROPHYLAXIS WITH MACROCYTIC LACTONES

Selamectin (Revolution®)

Moxidectin + imidicloprid (Advantage Multi®)

MONTHLY TOPICALS

Ivermectin (Heartguard®)

Milbemycin (Interceptor®)

MONTHLY ORAL TABLETS

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QUESTION TIME

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Toxocara cati

Ancylostoma tubaeforme

Dipylidium caninum

Taenia taeniaeformis

COMMON FELINE GI HELMINTHS

Photos courtesy of the NCVP

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LIFE CYCLE OF TOXOCARA CATI

Larvae may be shed in milk and ingested by neonates

Adult ascarids in small intestine

Eggs pass in feces and larvate

Host ingests PH with larvae arrested in tissue

Host ingests infective eggs with larvae

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LIFE CYCLE OF ANCYLOSTOMA TUBAEFORME

Adult hookworms in small intestine Host ingests

PH with larvae arrested in tissue

Host ingests infective larvae

Larvae penetrate

skin of host

Eggs pass in feces and larvate

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DIPYLIDIUM CANINUM: LIFE CYCLE

Proglottids containing egg packets pass in feces

Ingested by flea larvae

Develop into infective cysticercoids in the developing flea

Cysticercoid in ingested flea develop into adults in the small intestine

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TAENIA TAENIAEFORMIS: LIFE CYCLE

Develop into infective cysticercoids in the developing flea

Eggs released from proglottids into environment

Rodent intermediate host ingests eggs

Tapeworm proglottids containing infective eggs pass in feces

Cat infected by eating intermediate host

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116 adult cats examined

Gl tract examined at necropsy, helminths collected

Determine the prevalence of intestinal parasites including

– Toxocara cati

– Ancylostoma tubaeforme

– Physaloptera spp.

– Cestodes

Determine the utility of common diagnostics

FELINE PARASITE PREVALENCE STUDY1

1. Adolph C., 2013. Prevalence, disease implications, and diagnostic assays for parasites and vector-borne infections of cats in NE Oklahoma. Master’s Thesis

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&uact=8&docid=p7KqnnQCRYk9pM&tbnid=6ilpdrLuhEC08M:&ved=0CAcQjRw&url=http://liveruneat.wordpress.com/2011/03/04/muddy-shoes/&ei=pt0hVOPZN8nkoASu-YJI&bvm=bv.75775273,d.aWw&psig=AFQjCNF0t-fyCpw1GyE3qQqe8n162bNt_g&ust=1411591936398985

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Ascarids in 48/116 (41.4%)

Hookworms in 8/116 (6.9%)

Physaloptera in 3/116 (2.6%)

RESULTS1 (CONT.)



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Cestodes in 63/116 (54.3%) cats

– Dipylidium caninum: 40/116 (34.5%)

– Taenia taeniaeformis: 30/116 (25.9%)

– Co-infection with both: 7/116 (6.0%)

RESULTS (CONT.)

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T. cati

– Centrifugation: 37/48 (77.1%)

– Passive: 33/48 (68.8%)

A. tubaeforme

– Centrifugation 8/8 (100%)

– Passive 2/8 (25%)

Physaloptera

– Both methods 0/3 (0%)

RESULTS: DIAGNOSTIC TESTS1



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T. taeniaeformis

– Centrifugation: 8/30 (26.7%)

– Passive: 3/30 (10%)

– Proglottids identified: 6/30 (20%)

D. caninum

– Centrifugation: 0/40 (0%)

– Passive: 0/40 (0%)

– Proglottids identified: 6/40 (15%)

RESULTS: DIAGNOSTIC TESTS (CONT.)

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T. cati

– 7.2 (1-35)

D. caninum

– 10.3 (1-63)

– 5 cats have over 20 adult D. caninum

T. taeniaeformis

– 12.5 (1-56)

– 5 cats had over 35 adult T. taeniaeformis

– Cestode mass in 1 cat weighed 34.4 grams (1.5% of cat’s body weight)

INTENSITY: HELMINTHS

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NOW FOR SOMETHING WE CAN SEE

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www.zoetisus.com

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When an owner reports still seeing fleas despite initiation of insecticidal medications think life cycle first and resistance last

How long has therapy been ongoing?

What medications are being used?

Are ALL pets in the environment on PROPER medications?

Environmental factors

FLEA; KEY CONSIDERATIONS

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Helminths very common in cats in this study

Detection techniques failed to identify MOST tapeworms

Detection techniques failed to identify infections in some cats with T. cati

– Improved diagnostic techniques may allow detection of infections currently overlooked

Fleas are common ectoparasites of cats, but ticks also found

– Supports importance of routine heartworm and flea prevention for cats

CONCLUSIONS1


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