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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
LIFE CYCLE OF DIROFILARIA IMMITIS IN THE CAT
Microfilaria
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L1
L2 L3
LIFE CYCLE OF DIROFILARIA IMMITIS IN THE CAT
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
LIFE CYCLE OF DIROFILARIA IMMITIS IN THE CAT
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
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
Months after Infection
Ab
Ag ?
Microfilariae?
FELINE HEARTWORM DISEASE: CLINICAL TIMELINE
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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
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THE ACUTE DEATH SYNDROME IN FELINE HEARTWORM DISEASE
FELINE HEARTWORM INFECTION
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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
FELINE HEARTWORM INFECTION
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FELINE HEARTWORM DIAGNOSIS
(Ab- & Ag-)
Preventative
ANTIBODY AND ANTIGEN TEST
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FELINE HEARTWORM DIAGNOSIS
(Ab- & Ag-)
Preventative
ANTIBODY AND ANTIGEN TEST
L4-Early Adult infection/ Previous Adult infection
Preventative Discuss Potential Complications
+/- Thoracic radiographs +/- Echocardiography +/- Angiography
(Ab+ & Ag-)
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FELINE HEARTWORM DIAGNOSIS
(Ab- & Ag-)
Preventative
ANTIBODY AND ANTIGEN TEST
L4-Early Adult infection/ Previous Adult infection
Preventative Discuss Potential Complications
Positive HW Diagnosis
+/- Thoracic radiographs +/- Echocardiography +/- Angiography
(Ab+ & Ag-)
No Approved or Recommended
Treatment
Supportive Care and
Preventative
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FELINE HEARTWORM DIAGNOSIS
(Ab- & Ag-)
Preventative
ANTIBODY AND ANTIGEN TEST
L4-Early Adult infection/ Previous Adult infection
Preventative Discuss Potential Complications
Positive HW Diagnosis
(Ab+ & Ag+)
+/- Thoracic radiographs +/- Echocardiography +/- Angiography
(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
FELINE HEARTWORM INFECTION
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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
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1. American Heartworm Society Current Feline Guidelines 2014 http://www.heartwormsociety.org/
FELINE HEARTWORM DISEASE –TREATMENT1
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
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Intravenous
Basket Catheter
Accidental Worm Transection → Acute Death
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1. American Heartworm Society Current Feline Guidelines 2014 http://www.heartwormsociety.org/
FELINE HEARTWORM DISEASE –TREATMENT1
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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1. American Heartworm Society Current Feline Guidelines 2014 http://www.heartwormsociety.org/
FELINE HEARTWORM DISEASE –TREATMENT1
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
FELINE HEARTWORM INFECTION
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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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Photos courtesy of the NCVP
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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Photos courtesy of the NCVP
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
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Ascarids in 48/116 (41.4%)
Hookworms in 8/116 (6.9%)
Physaloptera in 3/116 (2.6%)
RESULTS1 (CONT.)
Photos courtesy of the NCVP
1. Adolph C., 2013. Prevalence, disease implications, and diagnostic assays for parasites and vector-borne infections of cats in NE Oklahoma. Master’s Thesis
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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
Photos courtesy of the NCVP
1. Adolph C., 2013. Prevalence, disease implications, and diagnostic assays for parasites and vector-borne infections of cats in NE Oklahoma. Master’s Thesis
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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
1. Adolph C., 2013. Prevalence, disease implications, and diagnostic assays for parasites and vector-borne infections of cats in NE Oklahoma. Master’s Thesis
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