Echinococcus granulosus in northern Queensland. 2. Ecological determinants of infection in beef cattle

To provide information on possible ecological determinants of infection with Echinococcus granulosus in a beef pastoral area of northern Queensland.

An ecological study was carried out on the prevalence and viability of infection with Echinococcus granulosus in definitive and potential intermediate hosts, and their predator prey relationships. Seven adjacent extensive beef properties 100 km south of Townsville, that included areas of savannah, open woodland and dense closed scrub, were selected for the study. Infection with E granulosus in dingoes was determined at post mortem, and in domestic dogs by examining duodenal mucus after purging with arecoline hydrobromide. Cattle, wild pigs and macropods were examined at post mortem for viable hydatid cysts. The diet of dingoes was investigated by identifying the hair of prey species found in their stomach and colon, and that of domestic dogs by questioning their owners.

Prevalence of hydatidosis in adult cattle ranged from 41% in animals from properties with large areas of dense closed scrub, to 3% on properties with little or no scrub. Hydatid cysts were found in 21.8% of black-striped wallabies (Macropus dorsalis), 9.4% of feral pigs, 1.5% of wallaroos (Macropus robustus), and 1.4% of eastern grey kangaroos (Macropus giganteus). No rufous rat kangaroos (Aepyprymnus rufescens) or swamp wallabies (Wallabia bicolor) were infected. Most cysts in macropods were viable, whereas in pigs about half were viable and in cattle only 0.7% contained viable protoscoleces. Infection with E granulosus was detected in 76% of dingoes, whereas no infection was detected in domestic dogs in the study area.

It was concluded that the sylvatic cycle of E granulosus in the study area was maintained mainly through predation of black-striped wallabies by dingoes, and that the verges of dense scrub were the main nidus of infection.