IN ANIMALS continued
CLINICAL DISEASE • Adult worms inhabit the small intestine of the definitive host and are not known to cause clinical
dogs in eastern Australia used coproantigen testing to detect E. granulosus. 11 The prevalence was 1.9% on the mainland (NSW, ACT, Qld, Vic) and 7.8% in Tasmania. The collection of faecal samples in Tasmania was more targeted than on the mainland, involving only rural dog owners living in the northern quarter of the state, where hydatid-infected cattle had previously been identified. • A 2006 study of rural domestic dogs in farming areas detected E. granulosus coproantigens in 29% of dogs from farms in south-eastern NSW and 17.5% of dogs from farms in Victoria. 12 The majority of E. granulosus coproantigen-positive dogs occurred on farms with more than five dogs, where feeding commercial dry dog food was supplemented with wildlife carcasses. In the same study, 64% of owners in NSW and 95% of owners in Victoria admitted feeding raw meat of home- slaughtered animals or wildlife to their dogs. • Echinococcus granulosus in wild dogs has been documented across eastern Australia, with prevalence between 50% in peri-urban wild dogs in south-east Queensland, and up to 100% in wild dogs in NSW. 13,14
disease, even in animals with significant worm burdens. 1,9 • Case reports have documented rare instances of cystic echinococcosis in cats. These cases are hypothesised to be associated with immunosuppression. 2,3 DIAGNOSIS • Diagnosis of hydatid tapeworm infestation in a dog should be based on a history of access to raw offal. Clinical diagnosis via detection of eggs and proglottids on standard faecal flotations is unreliable and the eggs are morphologically identical to Taenia species. 1 Due to the zoonotic risk, direct examination of adult worms is not recommended. • Diagnostic techniques include the detection of coproantigens (by coproantigen-ELISA) and/or copro-PCR, however these tests are not currently commercially available. 15,16
TRANSMISSION
• Human infection occurs through accidental ingestion of eggs shed in dog faeces or close contact with an infected dog ( E. granulosus eggs can adhere to dog hair and are immediately infective). • Indirect transfer of E. granulosus eggs in contaminated food, water and soil can also cause infection.
IN HUMANS
PREVALENCE AND RISK FACTORS • Hydatid disease in humans is uncommon in Australia, with the majority of cases believed to have been acquired overseas rather than from local exposure. Annually, 80–100 cases of echinococcosis are diagnosed in Australia (0.4 cases per 100,000 population). Higher rates have been documented in rural north-east and south-east New South Wales in one study, with an annual index of infection of 23.5 cases per 100,000 population in some communities. 17,18 • Risk factors for human infection include previous episodes of echinococcosis, occupational and domestic exposure to dogs which consume raw offal, and travel to or from endemic areas. Children in endemic areas are likely to be at greater
risk given their frequently close association with dogs and poor hand hygiene. • Cystic echinococcosis in humans is not a Nationally Notifiable Disease in Australia.
CLINICAL DISEASE • Cystic echinococcosis is characterised by the growth of hydatid cysts in internal organs. The incubation
period in humans can vary from months to years. 19 • After ingestion, Echinococcus eggs hatch and release oncospheres in the small intestine, migrating through the circulatory system to the liver and other anatomical sites, where cyst development begins. 20
CONTENTS
56 Companion Animal Zoonoses Guidelines
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