Role of Companion Animals in emergence and transmission of Parasitic Zoonoses

Dr. M. Senthil Murugan, M.V.Sc Scholar EpidemiologyDr. D.K. Singh, Principal Scientist, Veterinary Public Health

Dr. Bhoj R Singh, Principal Scientist and Head, Division of Epidemiology

Companion animals?

•An animal that someone keeps for company and enjoyment (MacMillan dictionary)

•Dogs, Cats, rodents, birds, Fish and horses

Companion versus Stray dogs As Pets Stray Populations

• Human – Animal bond• Mental ,Physical and

Social well being

• Utility, sporting, assistance dogs – Blind & deaf

• Developing Countries – High Stray dogs population

• Share close relationship with humans

• In India 19 million Stray dogs

Traub, et al., 2005MacPherson et al., 2010

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

Disease in Companion animals

Parasitic Zoonotic Agent Disease in Humans

EchinococosisEcchinococcous

granulosesEchinococcus multilocularis

Cystic echinococcosisAlveolar echinococcosis

Toxoplasmosis Toxoplasma gondii Congenital and Ocular Toxoplasmosis

Toxacariasis Toxacara canis, Toxacara cati

Visceral and Ocular Larval Migrans

Ancylostomiasis Ancylostoma caninumA.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 Children are affected

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

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)

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

Giardia colonization of GI mucosa

Robertson et al., 2000

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

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 BTraub et al., 2004

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

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

Toxoplasmosis - Transmission• Tachyzoites – in milk of

IMH (Sheep, Goat and Cows)

• Tissue cysts or Tachyzoites – in meat or offal

• In unpasteurized milk• In raw uncooked meat –

Pig, Sheep• Oocyst in environment

and water (Dubey, 2004)

• Oocysts in Vegetables put vegetarians on risk

Tissue cyst (Tachyzoites)

Tissue breakdown periodically(Bradyzoite)

Reinfect host cellsTenter et al., 2000

Intermediate Host (IMH)

Toxoplasmosis in India

Species(1990 – 2000)

Seropreva-lence (%)

Reference

Women of Child bearing age

2226

Malhotra et al., 1991

Pal et al., 2011

Cattle and buffaloes 43Mathur et al.,

1991

Domestic Fowl 40 Devda et al., 1998

Sheep 23 Dubey et al., 1993

Goat 68 Dubey et al., 1993Tenter et al., 2000

T. gondii Oocyst Survival

Temperature

Survival period

1 to 4 o C 3 weeks-1 to – 8 o C 1 week

-12 o C Killed67 o C Killed

• Relatively resistant to changes in temperature

• In Soil > 18 months• In IMH 10 sporulated oocysts are

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

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

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Transmission of Ancylostomiasis• Ancylostoma braziliense - CLM

• A. caninum- eosinophilic enteritis

• A. ceylanicum – CLM, Anemia

• Tropical Humid Climate a major risk factor.

• Eggs remain viable in moist, shaded and sandy soil

• Puppies may got infection through transmammary route (mother’s milk)

• In Humans – percutaneous penetration by the parasite

Egg pass in feces

Hatch in conducive environment L2 Larvae

Percutaneous entry – Lungs – Cough up - intestine

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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

Geographical Distribution A. ceylanicum

Country

Human Pets

Bangkok

3.4% 58%

Laos 17.6 % 77.8 %

Malaysia

9.1 % 74%

Bowman et al., 2010

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

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

Emergence of EchinoccosisCountry Early 1950 Late 1990 / 2000Bulgaria 6.5/Lakh population 15.8 / lakh population

Kazakhstan 1.4/lakh population 3.6 / lakh populationChina - 8.7/ lakh population

Argentina - 14900 / lakh population

Brazil - 5000/ lakh populationUruguay - 12.4/ lakh population

Causes of reemergence:•Political instability•Administrative irregularities•Economic changes• Reduced Funds for control

•Control measures are not followed•AE – dog ownership•Urban foci – feeding offals

Eckert, 2009

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

Toxacara eggs survive in soil• At optimal environment,

eggs 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

Toxacara eggs in Barielly

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

Potential Puppies !!!Pups Adults

• 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 –

better development of egg

• 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

Roddie et al., 2008

LeishmaniasisTransmission• 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

Life cycle of Leishmania Sp

Emergence of Leishmania in RajastanSpecies Percent

PrevalencePet Dogs 24

Street dogs 21Humans 68.04

• Cutaneous leishmaniasis – Leishamania tropica

• Dogs -Cutaneous lesions in face, nostril, eyes and extremities

• 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

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

Other Emerging Parasitic ZoonosesDisease Etiology Vector / source Country

BabesiosisBabesia canis, B.

conrade Ixodes ricinus USA

Chagas Disease (American

trypanosomiasis) Trypanosoma cruzi Triatomine bugs USA

Canine Heart worm Dirofilaria immitis Ctenocephalides canis USA

Murine typhus Rickettsia typhi Ctenocephalides felis USA

Canine Heart wormAcanthochelionema

reconditum Ctenocephalides canis USA

Paragonimiasis (Lung Fluke)

Paragonimus westermanii Crabs, cray fish China

Clonorchiasis Clonorchis sinensis Fish, shrimp China

Trichnosis Trichinella spiralis Dog meat China

Traversa et al., 2013

Other Pet animal & Parasitic zoonoses

Species Zoonotic parasitic diseaseHorses Trichuriasis, HydatidosisRabbits  Cheyletiella parasitivorax (Mite)

Rats Hymenolepis diminuta (Cestode)Rodents Trixacarus caviae (Acarid)Snakes Pentostomiasis (Armillifer armillatus)

FishClonorchiasis, Diphyllobothriosis,

Gnathostomiasis

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

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 washingMacpherson, 2005