Growth and genotypes of Echinococcus granulosus found in cattle imported from Australia and fattened in Japan
Graphical abstract
Highlights
► Cystic hydatidosis in imported cattle from Australia to Japan was investigated. ► The occurrence at the abattoir on study in the last 5 years was 1.8%. ► Most of the cysts were valid, having thin germinal and laminated layers. ► Protoscoleces were found in the 3 largest cysts obtained from 3 (2.9%) cattle. ► Genotype of most cysts was G1 but G2 and G3 genotypes were also detected.
Introduction
Echinococcus granulosus is one of the most important zoonotic parasites causing the cystic hydatid disease in humans, domestic livestock and wildlife worldwide. E. granulosus is now recognized to be constituted of a number of biologically and genetically distinct entities referred to as strains, subspecies or distinct species [1]. Transmission of the parasite occurs predominantly in a synanthropic cycle with domestic dogs as definitive hosts and livestock animals as intermediate hosts. At present, it is considered that E. granulosus does not complete and maintain its life-cycle in Japan. However, the cysts of the parasite have been detected in cattle imported from foreign countries and fattened for certain period in Japan. Studies on such cases have been intensively conducted in the 1980s, showing the occurrence of 15.3 to 78.3% in cattle imported from Australia [2], [3], [4], [5].
In Australia, E. granulosus was introduced with domestic animals about 200 years ago during European settlement. Since dingoes and macropods played suitable definitive and intermediate hosts, respectively, the parasite established its lifecycle in wildlife, thus rendering control program difficult. It has been considered that two strains of E. granulosus have been distributed in Australia, common sheep strain (G1 genotype) in the mainland and Tasmanian sheep strain (G2 genotype) in Tasmania island [6]. However, by an intensive control program, provisional eradication was announced in Tasmania Island in 1996. In contrast, the parasite remains prevalent and widespread in the mainland despite the conduction of several control campaigns [7].
In Japan, importation of live cattle from foreign countries is still continued and a significant number of live cattle have been imported from Australia every year. Despite of the fact, studies on E. granulosus in imported cattle have not been conducted since the 1990s. Therefore, to contribute to the assessment of the present risk of E. granulosus in Japan, the occurrence of hydatidosis in imported cattle was investigated at an abattoir in Miyazaki where a large number of imported cattle were processed annually, and the growth and genotypes of the parasite metacestodes detected were examined in this study.
Section snippets
Statistical survey
Occurrence of hydatidosis in imported cattle slaughtered at an abattoir on study in Miyazaki, Japan, during the recent 5 years was investigated by referring to the Task Overview of Meat Inspection Centers of Miyazaki prefecture in 2006 to 2010. Then an interview was conducted with the representative person of the abattoir in order to obtain information on the importation frequency and the subsequent fattening procedures of cattle in Japan. Furthermore, to assess the overall rate of imported
Occurrence of hydatidosis in imported cattle
In average, 9537 imported cattle from Australia were slaughtered annually at the abattoir on study in the last 5 years (2006 to 2010) and hydatid cysts were constantly detected in about 1.8% (1.4 to 2.1% annually) of the cattle (Table 1). Table 1 also shows annual total numbers of imported cattle to Japan from foreign countries during 2004 to 2009. Most of the cattle were imported from Australia: about 20,000 and 1300 cattle were imported annually as fattening and breeding cattle, respectively.
Discussion
Compared to the results of similar studies conducted on imported cattle from Australia in the 1980s [2], [3], [4], [5], the occurrence of E. granulosus in the abattoir on study during the last 5 years was low (15.3–78.3% vs. 1.8%). The statistical data of the annual number of imported cattle slaughtered in the abattoir and the annual number of fattening cattle imported from Australia to Japan would indicate that about 40–60% of imported fattening cattle were annually processed in this facility
Acknowledgments
We are grateful to the staff of the Laboratory of Veterinary Parasitic Diseases, Department of Veterinary Sciences, Faculty of Agriculture, University of Miyazaki for their valuable support. We also thank the staff of the abattoir on study and the Meat Inspection Center of Miyazaki prefecture for providing samples and information related to this study. Part of this work was supported by the Strategic Japanese–Chinese Cooperative Program of Japan Society and Technology Agency, and by the
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