HYDATID DISEASE OF ANIMALS IN AUSTRALIA

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.

First report of Taenia ovis infection in Danish sheep (Ovis aries)

We report Taenia ovis infection in Danish sheep for the first time. In spring 2016, the metacestode stage of T. ovis was at slaughter observed in heart muscles, diaphragm and skeletal muscles from approx. a third of all sheep from one specific farm localised in South Jutland. The diagnosis was confirmed by molecular typing of the mitochondrial cytochrome c oxidase I (cox1) gene. Three newly imported dogs were suspected but the definitive host was unidentifiable. The finding is not regulated in the meat control procedures. However, infected meat is usually condemned due to aesthetic reasons causing economic losses. Thus, finding of T. ovis is of concern to sheep meat producers in the area, as the infection could have spread further on to other farms.

Survey for hydatidosis in cattle bred in the northern region of the Northern Territory of Australia

OBJECTIVE

To determine whether hydatidosis occurs in cattle bred in the northern region of the Northern Territory.

DESIGN

A survey utilising two stage sampling was designed to provide 95% confidence of detecting hydatids in cattle with a herd prevalence of 10% and animal prevalence of 10%.

PROCEDURE

For a 1 year abattoir killing season, lesions from the liver and/or lung were collected from 4348 cattle being slaughtered at a Northern Territory abattoir and examined for hydatid cysts. The origin of cattle was established through identification of the brand.

RESULTS

Sample sizes of 41 or more Northern Territory bred cattle were achieved for each of 29 properties. No hydatid cysts were found in cattle bred in the northern region of the Northern Territory.

CONCLUSION

This study provides evidence that a cycle of hydatid transmission does not occur in the northern region of the Northern Territory.

Australasian contributions to an understanding of the epidemiology and control of hydatid disease caused by Echinococcus granulosus--past, present and future

For several years after Echinococcus granulosus was introduced into Australasia from Europe, its life cycle was unknown. Before the end of the 19th century, however, Cystic Hydatid Disease (CHD) was recognized in humans as an important cause of death, although its magnitude was not quantified. During the first 50 years of the 20th century, the urban component declined, but CHD remained a serious source of ill-health. During the second half of the 20th century major research contributions have included: (i) differentiation of pastoral from wildlife Echinococcus and (ii) breaking the 'epidemiological code' of the family Taeniidae, thereby defining the conditions under which transmission occurs. Based on this research and concurrent surveys, it is concluded that the present geographical distribution of E. granulosus in domestic animals and CHD in the rural population is determined by climate; being uncommon where hot dry seasons continue beyond a few months. The parasite's range may be extended in its wildlife cycle through a highly susceptible definitive host--the dingo. The ease with which blowflies transfer taeniid eggs from dog faeces to animal and human foodstuffs implies that in Australasia, CHD can sometimes be regarded as foodborne. A perceived decline in autochthonus cases in the rural community during the second half of the 20th century may be accounted for by increased standards of living generated by economic advancement. Where a decline has not occurred or incidence is unusually high, CHD may be acting as an indicator of social disadvantage. Field trials and control programmes demonstrated that pastoral echinococcosis readily responded to intervention. Indeed, in both New Zealand and Tasmania, using different administrative structures and methods of funding, E. granulosus was driven from endemic towards extinction status. The really convincing result was the rapid decline in CHD in all age groups. The problem still to be solved is to identify methods for eliminating foci where high levels of CHD still exist but, continent- or even state-wide intervention may not be considered to be cost-effective using current tools. Here, mathematical modelling and cost-benefit analysis can be regarded as powerful methods to assist the decision-making process.

A meatworks survey of bovine hydatidosis in southern Queensland

A meatworks survey was undertaken in 1981-82 to define the distribution and prevalence of hydatidosis in beef cattle in southern Queensland. Hydatid cysts, mostly degenerate, were found in 14.6% of the 22,916 animals examined. The endemic area was to the east of a line approximating the 500 mm isohyet. Prevalence varied with age and origin of cattle, but not sex. Prevalence increased linearly with age, at least up to 4 years. Prevalence on the east coast ranged from 4.3% in yearlings to 52.2% in 4-year-old cattle. At the western limit of the endemic area, the prevalence ranged from 1.4% in yearlings to 10.8% in 4-year-olds. On the Darling Downs, prevalence was highest in areas where cattle raising is the main industry. On the south western Downs, where sheep-farming predominates, the prevalence in cattle was much lower, probably because of fewer dingoes. Livers only were affected in 46.5% of infected cattle, lungs only in 17.7%, and 35.8% of infected animals had both organs affected. Infection in other organs was uncommon. A detailed study of 133 infected cattle showed that 3.8% had lesions misdiagnosed as hydatid cysts at slaughter.

Hydatid disease: epidemiology and pathology

Information regarding the epidemiology and pathology of Echinococcus granulosus in Australasia is not well presented in standard surgical textbooks. This review presents the basic science of E. granulosus in Australasia, emphasizing those areas which are not well known, are misunderstood, or are of particular relevance to current surgical practice.

The susceptibility of the European red fox (Vulpes vulpes) to infection with Echinococcus granulosus of Australian sheep origin

A detailed comparative study was made of the development of Echinococcus granulosus of Australia sheep origin in European red foxes (Vulpes vulpes) and dogs. No significant differences in growth, segmentation or maturation of the parasite between dogs or foxes was found, although worm burdens were slightly lower in foxes than in dogs. It is concluded that although the role of foxes in the epidemiology of hydatidosis in Australia may not be significant, foxes should nevertheless be regarded as potential definitive hosts of the Australian strains of E. granulosus.