Revisiting cyst burden and risk factors for hepatic hydatid disease (Echinococcus granulosus sensu stricto) in Australian beef cattle

The characteristics and risk factors associated with hepatic Echinococcus granulosus sensu stricto infection (hydatid disease) were investigated in beef cattle slaughtered at an abattoir in eastern Australia. Sampled cattle were sourced from all eastern states, predominantly from regions associated with the Great Dividing Range. Livers and corresponding demographic data were collected from 601 carcasses. Livers were examined for the number, size, viability, and fertility of hydatid cysts. Mixed effects logistic regression was used to evaluate associations of sex, feed-type (grass- or grain-fed), and dentition (age) on hydatid disease. Hydatid cysts were detected in all dentition groups. The most commonly sampled dentition group was zero-tooth cattle (less than 18 months). Twenty-nine percent of infected livers had only one cyst, and 48% of infected livers contained viable cysts. Thirty-seven percent of infected livers had cysts that were 3-10 mm in diameter. The size and number of cysts were positively correlated with age of the animal. Regression analysis showed that the odds of hydatid disease were highest in eight-tooth cattle (>42 months; OR 26.9; 95% CI 11.8-61.6; reference level [ref] zero-tooth). Being grass-fed was also significantly associated with the presence of hydatid disease (total effect; OR 3.0; 95% CI 1.7-5.5; ref grain-fed). Although there was no evidence of a total effect of sex across the study population, males of a given dentition group and feed-type (grass- or grain-fed) were more likely to be infected than respective females. Despite changes in Australian agriculture in the last 30 years, the burden (number, size, and viability of cysts) of hydatid disease in individual infected animals remains similar to previous Australian studies.