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【目的】戊型肝炎病毒(Hepatitis Evirus,HEV)感染是一种人畜共患病,而猪是HEV的病毒储库。在日本,HEV感染已成为猪的地方性猪病。阐明HEV在猪场中的详细传播机制,将有利于人们掌握特定年龄段猪群的感染状况,尤其是肉猪在屠宰前的感染状况。【结果】本文,作者重新分析了源于日本猪场的一个大型猪HEV血清阳性率数据集,以此评估HEV的感染力。结果表明,北海道、本州和九州三个地区猪场中的猪HEV感染力分别为3.45×10-2/d(95%的置信区间(下同):3.17～3.75×10-2/d)、2.68×10-2/d(2.28～3.14×10-2/d)和3.11×10-2/d(2.76～3.50×10-2/d)。利用作者建立的模型得到的估测结果表明,猪感染HEV的平均日龄在59.0～67.3d之间,其基本传染数R0按4.02～5.17的数量级递增。对特定年龄猪群在不同感染力下的敏感性分析显示,HEV感染力下降将提高猪感染HEV的年龄,而且会增加180日龄时散毒猪的数量。【结论】尽管作者的研究表明95%以上的猪是在150日龄前被感染的,但该模型显示感染力下降可以增加感染猪将HEV传播给人的风险。如果感染力开始下降,就有必要采取基本的应对策略(如在哺乳期末将未感染猪与感染猪分开)以最大限度地减少肥育阶段的HEV阳性猪数量。
【Objective】 Hepatitis virus (HEV) infection is a kind of zoonosis, while pigs are the virus reservoir of HEV. In Japan, HEV infection has become endemic pig disease in pigs. Elucidating the detailed transmission mechanism of HEV in pig farms will help people understand the infection status of pigs of a certain age group, especially the status of the pigs before slaughter. [Results] In this paper, the authors reanalyzed the HEV seroprevalence data from a large pig HEV seroprevalence data collection from a Japanese farm. The results showed that the HEV infectivity of swine farms in three districts of Hokkaido, Honshu and Kyushu were 3.45 × 10-2 / d (95% confidence interval, 3.17-3.75 × 10-2 / d) 2.68 × 10-2 / d (2.28 ~ 3.14 × 10-2 / d) and 3.11 × 10-2 / d (2.76 ~ 3.50 × 10-2 / d). The estimation results obtained by using the model established by the author showed that the average age of pigs infected with HEV ranged from 59.0 to 67.3 days, and the basic infection number R0 increased on the order of 4.02-5.17. Sensitivity analysis of pigs at particular ages at different levels of infection showed that a decrease in HEV infectivity would increase the age of pigs infected with HEV and would increase the number of litter pigs at 180 days of age. [Conclusion] Although the authors’ study showed that over 95% of pigs were infected before 150 days of age, this model shows that reduced infectivity can increase the risk of HEV transmission in infected pigs. If infectivity begins to decline, it is necessary to take a basic coping strategy (such as separating uninfected and infected pigs at the end of lactation) to minimize the number of HEV-positive pigs in the finishing stage.