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Role of companion animals in emergence and transmission of Parasitic Zoonoses
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Role of companion animals in emergence and transmission of Parasitic Zoonoses


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Several parasitic infections and infestation are common in developing countries where companion animals (dog and cats) play an important role. The presentations talks about a few important ones .

Several parasitic infections and infestation are common in developing countries where companion animals (dog and cats) play an important role. The presentations talks about a few important ones .

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  • Increased pet owners in urban areas and high stray populations, Companion animals share 60 of the zoonotic diseases.
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    • 1. Role of Companion Animals in emergence and transmission of Parasitic Zoonoses Dr. M. Senthil Murugan, M.V.Sc Scholar Epidemiology Dr. D.K. Singh, Principal Scientist, Veterinary Public Health Dr. Bhoj R Singh, Principal Scientist and Head, Division of Epidemiology
    • 2. Companion animals? • An animal that someone keeps for company and enjoyment (MacMillan dictionary) • Dogs, Cats, rodents, birds, Fish and horses
    • 3. Companion versus Stray dogs As Pets • Human – Animal bond • Mental ,Physical and Social well being • Utility, sporting, assistance dogs – Blind & deaf MacPherson et al., 2010 Stray Populations • Developing Countries – High Stray dogs population • Share close relationship with humans • In India 19 million Stray dogs Traub, et al., 2005
    • 4. Who are at risk ? Those in need of companion and---. 1. Immuno Compromised individuals- AIDS, Cancer, Organ and Bone marrow transplants, Steroid therapy 2. Children, Geriatrics 3. Pregnant Women 4. Veterinary professionals 5. Animal handler / Researcher Robertson et al., 2000
    • 5. Parasitic Zoonotic Agent Disease in Humans Echinococosis Ecchinococcous granuloses Echinococcus multilocularis Cystic echinococcosis Alveolar echinococcosis Toxoplasmosis Toxoplasma gondii Congenital and Ocular Toxoplasmosis Toxacariasis Toxacara canis, Toxacara cati Visceral and Ocular Larval Migrans Ancylostomiasis Ancylostoma caninum A.ceylanicum Cutaneous Larval Migrans Giardiasis Giardia duodenalis GI disturbances Cryptosporidiosis Cryptosporidum canis, C.felis Rare infection Leishmaniasis Leishmania donovani Cutaneous and Visceral Leishmaniasis Dipylidiasis Dipyllidium caninum Disease in Companion animals Children are affected
    • 6. Human behavior and emergence of parasitic zoonoses • Growing global population (>6.4 billion) causing: 1. Exploitation of natural environment, e.g. AE 2. Urbanization – Inadequate sanitation and garbage disposal. 3. High percapita garbage – more stray dogs. 4. Breeding sites for vectors e.g. Leishmaniasis in dogs. 5. Inappropriate feeding: Uncooked meat (Smoked & cured) e.g. Toxaplasma cysts. Feeding offals to dogs may lead to Echinoccosis. 6. Poor hygiene – Lower economic strata, so many faeco-oral infections. Macpherson, 2005
    • 7. Dogs as Mechanical Carriers • Mechanical reservoir for human parasites • Host specific human parasites – Ascaris lumbricoides, Trichuris trichiura, Hymenolepis diminuta and Isospora belli • Viable Ascarid eggs isolated from 30 % of dog feces in Assam (Traub et al., 2005) • Fur of dogs – Carry T. gondii to humans (Tenter et al., 2000)
    • 8. Factors for Emergence of GI Protozoans • Western world & Urbanization – regular deworming of pets • Enteric protozoans remains unaffected by anthelminthics • Intestinal protozoans (Giardia and Cryptosporidium) may be colonizing the niche vacated by T. canis and D. caninum and other helminths killed by anthelmintics. • Pet ownership Robertson et al., 2000 Giardia colonization of GI mucosa
    • 9. Transmission of Giardiasis • Giardia duodenalis - Humans are reservoir • Zoonotic strains of Assemblage AI, AII and B – from dogs • Cysts – infective stage, prolonged survival of cysts in environment (Weeks to months) • Ingestion of food, water or arthropods carrying cysts. • 10 – 100 cysts sufficient for Direct fecal - oral and water borne transmission Thurtson et al., 2002
    • 10. Emergence Giardiasis in Assam • Type A 39 % & B 61% in humans • Same Genotype in the same village and the same house hold both in Dogs & Humans • Human isolates - Assemblage A or B and that all found in Dog isolates • Dog was infected through Coprophagy of human feaces • Multi-dog in household are more prone for infection • Dogs infected with own host adapted Assemblage C & D, and also with Zoonotic genotypes A and B Traub et al., 2004
    • 11. Minimal zoonotic risk & Cryptosporidiosis • C. canis and C. felis oocysts are common in feces dogs and Cats • Human cases are associated with C. hominis and C. parvum • Molecular epidemiologic studies proves low risk of zoonotic transmission • Rarely immunocompromised pet owners may acquire the infection from dogs. Forster et al., 2010 Lifecycle of Cryptosporidium sp
    • 12. Transmission of Toxoplasmosis • Toxoplasma gondii from Cats • Highly resistant oocytes • Asexual stages in intermediate host (IMH) – all vertebrates • In Pregnancy – Vertical transmission • Cats excrete oocysts for 20 days of infection • Reinfection infection after 6 yrs, however under immunosupression cats starts to excrete oocysts Tenter et al., 2000
    • 13. Toxoplasmosis - Transmission • Tachyzoites – in milk of IMH (Sheep, Goat and Cows) • Tissue cysts or Tachyzoites – in meat or offal Intermediate Host (IMH) Tissue cyst (Tachyzoites) • In unpasteurized milk • In raw uncooked meat – Pig, Sheep • Oocyst in environment and water (Dubey, 2004) • Oocysts in Vegetables put vegetarians on risk Tenter et al., 2000 Tissue breakdown periodically (Bradyzoite) Reinfect host cells
    • 14. Toxoplasmosis in India Species Seropreva- (1990 – 2000) lence (%) Reference 22 Malhotra et al., 1991 26 Pal et al., 2011 Cattle and buffaloes 43 Mathur et al., 1991 Domestic Fowl 40 Devda et al., 1998 Sheep 23 Dubey et al., 1993 Goat 68 Dubey et al., 1993 Women of Child bearing age Tenter et al., 2000
    • 15. T. gondii Oocyst Survival • Relatively resistant to changes in temperature • In Soil > 18 months • In IMH 10 sporulated oocysts are Temperature Survival period 1 to 4 o C 3 weeks -1 to – 8 o C 1 week -12 o C Killed 67 o C Killed sufficient for infection • For Cats 100 oocysts are required for infection • Varying excystation (Dubey,1996) • Tissue cyst are resistant to Digestive enzymes & also • Resistant to chemical and disinfectants (Dubey,1996) Tenter et al., 2000
    • 16. Emergence of Toxoplasmosis • One third of world population is exposed • Seroprevalence is high –in meat consumers (mutton, beef, pork), in Pregnant women (Pal,2011) • Consumption of uncooked meat, smoked , cured meat enhances risk in IMH
    • 17. 17 Transmission of Ancylostomiasis • Ancylostoma braziliense - CLM • A. caninum- eosinophilic enteritis • A. ceylanicum – CLM, Anemia Egg pass in feces • Tropical Humid Climate a major risk factor. • Eggs remain viable in moist, shaded and sandy soil • Puppies may got infection through Hatch in conducive environment L2 Larvae transmammary route (mother‟s milk) • In Humans – percutaneous penetration by the parasite Percutaneous entry – Lungs – Cough up - intestine 17
    • 18. Re -Emergence of Ancylostoma ceylanicum • Ist discovered in 1913 - 9.3% prisoners in Calcutta • until 1960 erroneously referred with A. braziliense • Resurfaced 50 years later in South East Asia Bangkok, Loas, Thailand, Malaysia and Indonesia • Risk for communities with A. ceylanicum is endemic in dogs. • 62 % prevalence in India in stray dog and cats (Traub 2007) • Percutaneous infection / ingestion leads to Eosinophilic enteritis Bowman et al., 2010
    • 19. Geographical Distribution A. ceylanicum Country Human Pets Bangkok 3.4% 58% Laos 17.6 % 77.8 % Malaysia 9.1 % 74% Bowman et al., 2010
    • 20. Cystic Echinococcosis - Transmission • Echinococcus granulosus – G1- G10 strain • Unilocular cyst - all organs • Humans: G1 Strain, Sheep – dog cycle • Urban-cycle – feeding raw offals to dogs • Direct contact – fecal oral contact of eggs • Dogs Carry pathogen on - Hairs, muzzle, paws • May be transmitted indirectly – through contaminated food and water and through • Flies and other arthropods - Cockroaches Pedro Moro et al., 2008
    • 21. Alveolar Echinoccosis - Transmission • Echinococcus multilocularis • Sylvatic cycle– Fox • Dogs acquire infection by ingestion of Wild Rodents, lagomorphs (IMH) • Dogs pass the egg in feaces. • Cats are less susceptible than canids (Kapel, et al., 2006) Pedro Moro et al., 2008
    • 22. Emergence of Echinoccosis Country Early 1950 Late 1990 / 2000 Bulgaria 6.5/Lakh population 15.8 / lakh population Kazakhstan 1.4/lakh population 3.6 / lakh population China - 8.7/ lakh population Argentina - 14900 / lakh population Brazil - 5000/ lakh population Uruguay - 12.4/ lakh population Causes of reemergence: •Control measures are not followed •Political instability •AE – dog ownership •Administrative irregularities •Urban foci – feeding offals •Economic changes • Reduced Funds for control Eckert, 2009
    • 23. Transmission of Toxacariasis • Toxacara canis, T. cati are transmitted transplacentally, Transmammary to puppies and kittens. • Several forms: Visceral, neural, ocular and asymptomatic • Children acquire infection through ingestion of contaminated soil. • Infection on consuming ▫ raw liver food animals ▫ Uncooked vegetables • Direct Contact with embryonated eggs on dog hair Alice Lee et al., 2010
    • 24. Toxacara eggs survive in soil • At optimal environment, eggs Toxacara eggs in Barielly survive in soil for 2 – 4 yrs • In winter for 6 – 12 months • Cats bury their feces in soil • Egg contamination in play grounds, parks, garden (Manini et al., 2012) Sudhakar et al., 2013
    • 25. Dog hair in Toxacara Transmission? • Dogs harbour eggs of parasite in fur • Humans : Ingestion of embryonated eggs - picked form coat of dog • Eggs on Hairs in dorsal > perianal area • On hair: Higher densities of eggs than in soil. • Puppies are hugged and handled most – hence higher the risk of transmission. Wolfe & Wright , 2003 Rolling of Dogs
    • 26. Potential Puppies !!! Pups • Eggs in hair: 95% • Worm infestation 80 % • Strong Positive correlation in Worms and eggs in hair • Contamination their own fur and litter mates • Embryonated egg 0.31 % (3 times) • Shorter hair, better heat transfer – Adults • Eggs in hair : 56% • Worm infestation 22.5% • No correlation in no. of worms and eggs in coat • Picked by rolling in environment contaminated with eggs • Embryonated egg 0.12% • Adult hairs – non conducive for embryonation of egg better development of egg Roddie et al., 2008
    • 27. LeishmaniasisTransmission Life cycle of Leishmania Sp • Leishmania infantum – ZVL • L. tropica – CL • Vector: Sand fly/ Phlebotomine sp • Major urban reservoir: Dogs • Infection in dogs proceeds occurrence in humans in particular geographical area Wendel Coura - Vital et al., 2013
    • 28. Emergence of Leishmania in Rajastan • Cutaneous leishmaniasis – Leishamania tropica • Dogs -Cutaneous lesions in face, nostril, eyes and extremities Species Percent Prevalence Pet Dogs 24 Street dogs 21 Humans 68.04 • Humans – chronic non healing ulcers • Infected street dogs – transmission to humans • Increased humidity and near Rajasthan canal – breeding for sand flies • Presence of infected dogs in corresponding area – increased prevalence in humans Sharma. et al., 2003
    • 29. Transmission of Dipylidiasis • Dipylidium caninum – Cestode of Dogs • Humans - accidental host • Flea vector - Cysteicercoid • Ctenocephalides canis, C. felis • Ingestion of fleas – Children Develop in to adult worms Life cycle of Dipylidium Caninum
    • 30. Other Emerging Parasitic Zoonoses Disease Vector / source Country Babesiosis Etiology Babesia canis, B. conrade Ixodes ricinus USA Chagas Disease (American trypanosomiasis) Trypanosoma cruzi Triatomine bugs USA Canine Heart worm Dirofilaria immitis Ctenocephalides canis USA Rickettsia typhi Ctenocephalides felis Acanthochelionema Canine Heart worm reconditum Ctenocephalides canis Paragonimiasis (Lung Paragonimus Fluke) westermanii Crabs, cray fish USA Murine typhus USA China Clonorchiasis Clonorchis sinensis Fish, shrimp China Trichnosis Trichinella spiralis Dog meat China Traversa et al., 2013
    • 31. Other Pet animal & Parasitic zoonoses Species Zoonotic parasitic disease Horses Rabbits Rats Rodents Snakes Trichuriasis, Hydatidosis Cheyletiella parasitivorax (Mite) Hymenolepis diminuta (Cestode) Trixacarus caviae (Acarid) Pentostomiasis (Armillifer armillatus) Clonorchiasis, Diphyllobothriosis, Gnathostomiasis Fish
    • 32. Persistence of parasitic zoonoses in India • 98 % of the dogs are not dewormed or vaccinated in India (Traub et al., 2002) • Poor hygiene • Over crowding urban areas • Disease burden is not known • Stray animals close contact with humans • Surveillance and control of Canine zoonoses – low prioritized Robertson et al., 2000
    • 33. Control of Parasitic Zoonoses • Veterinarians - Education of owners • Regular deworming and ectoparasite control • ABC – Stray animals • “Do not feed cysts to dogs” • Foreign countries „Scoop laws‟ • Urban sanitation • Changing eating habits – washing and cooking • Safe drinking water • Personal hygiene – Hand washing Macpherson, 2005