PII - Echinococcus

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E.g. granulosus:

Final host: dog, wild canids

Site: SI

IMH: ruminants, pig, man (zoonotic)

E.g. equinus:

Final host: dog, red fox

Site: SI

IMH: horse/donkey (not zoonotic)

Life cycle of E.g. granulosus: PPP 40-50 days

Gravid segments shed 1 per week

egg reistant

ingested by IMH

onchosphere released - penetrated S.I wall

hydatid cyst liver/lung (6+months p.i)

cyst ingested by final host

adults in SI dog

*takes 6 months to become mature

*pathology is associated with cystic stage not adult worm

IMH depends on local animal husbandry

in UK sheep is most important

can be camels or reindeers

sheep is natural IMH

In sheep most cysts are in lungs, whereas in horses and cattle most are in liver

* in cattle cysts are sterile = budding but not developing the infectious form so can't be transmitted (due to immune response)

Diagnosis:

- IMH in abattoir (sheep don't have any pathology unless cyst forms in unusual place rather than liver or lung

- Final host (dog) FEC, ELISA + PCR

Pathogenesis:

mostly well tolerated in IMH

most cases detected in abattoir

not pathogenic in dog final host

always of significance in humans (accidental intermediate host)

*zoonotic spread requires close man-dog contact - human becomes infected via ingestion of onchospheres from water, foodstuffs or coat of dog (wash hands after clapping dog)

Control of Hydatid disease:

regular deworming of dogs - Praziquantel

proper disposal of infected carcasses

deny access of dogs to abattoirs

hygiene

Echinococcus multilocularis

Final host: fox, dog, cat, other wild canids

IMH: rodents, man

Life cycle similar to E.g. granulosis

important zoonosis - prevalent in Europe

Life cycle: PPP 28-35 days

gravid segments shed in faeces

eggs resistant to -50 degrees

ingested by rodent IMH

embryo released penetrates SI wall

To liver, via hepatic portal vein. Rapidly vesiculates

cyst ingested by fox

adults in DI fox or dog

*sick animals are likely to be predated = pass on parasite

In humans:

causes alveolar echinococcosis in liver not lung

potentially fatal

long asymptomatic period (5-15 years) followed by clinical signs

Treatment: liver transplant, section or albendazole *shrink cyst then remove via surgery

Albendazole + surgery improves 10 year survival rates from 6-25% to 80-83%

*pet passport scheme has prevented it coming to UK