Taenia ovis: an emerging threat to the Chinese sheep industry?

Yadong Zheng

Taenia ovis is a tapeworm that is mainly transmitted between dogs and sheep. Although T. ovis infection is not a public health issue, it causes a great financial loss due to condemnation of carcasses.  The first outbreak of T. ovis infection in China occurred in 2015. Reassessment of adverse effects of T. ovis infection on Chinese sheep industry in future is necessary. The first T. ovis outbreak in China suggests that the epidemic situation across the country is underestimated. For the transmission of T. ovis, many factors, including eggs, dogs and wild canids, human behaviours and sheep trade, should be seriously considered. In blocking the transmission chain, regular treatments of the infected dogs using anthelmintics play a crucial step, but at the moment it is difficult to be fully executed in China, largely due to the behaviours, customs and faith of local farmers. Moreover, combined with no clinical symptoms in the infected adult sheep and goats, the lack of pre-mortem diagnostic tools makes it harder to practice a national wide surveillance as well as inspection and quarantine in increasingly frequent free sheep trade activities in China, leading to an inability to restrict T. ovis infection into small areas. Furthermore, the ongoing campaigns against Echinococcus granulosus may have an adverse effect on control of T. ovis infection because of no consideration of a role of dogs in the transmission of the parasite. Lack of national epidemic data, pre-mortem diagnostic reagents and vaccines severely hampers the implementation of disease control campaigns and the restriction of T. ovis infection into small areas. Consequently, sheep and goats are at an increasing risk of T. ovis exposure and the possibility of large-scale outbreaks across China in future is possible, causing great adversity towards sheep industry.