Isoda Norikazu, Baba Kairi, Ito Satoshi, Ito Mitsugi, Sakoda Yoshihiro, Makita Kohei
Unit of Risk Analysis and Management, Research Center for Zoonosis Control, Hokkaido University, Kita 20, Nishi 10, Kita-Ku, Sapporo 001-0020, Japan.
Global Station for Zoonosis Control, Global Institute for Collaborative Research and Education (GI-CoRE), Hokkaido University, Sapporo 001-0020, Japan.
Pathogens. 2020 Feb 13;9(2):119. doi: 10.3390/pathogens9020119.
The prolongation of the classic swine fever (CSF) outbreak in Japan in 2018 was highly associated with the persistence and widespread of the CSF virus (CSFV) in the wild boar population. To investigate the dynamics of the CSF outbreak in wild boar, spatiotemporal analyses were performed. The positive rate of CSFV in wild boar fluctuated dramatically from March to June 2019, but finally stabilized at approximately 10%. The Euclidean distance from the initial CSF notified farm to the farthest infected wild boar of the day constantly increased over time since the initial outbreak except in the cases reported from Gunma and Saitama prefectures. The two-month-period prevalence, estimated using integrated nested Laplace approximation, reached >80% in half of the infected areas in March-April 2019. The area affected continued to expand despite the period prevalence decreasing up to October 2019. A large difference in the shapes of standard deviational ellipses and in the location of their centroids when including or excluding cases in Gunma and Saitama prefectures indicates that infections there were unlikely to have been caused simply by wild boar activities, and anthropogenic factors were likely involved. The emergence of concurrent space-time clusters in these areas after July 2019 indicated that CSF outbreaks were scattered by this point in time. The results of this epidemiological analysis help explain the dynamics of the spread of CSF and will aid in the implementation of control measures, including bait vaccination.
2018年日本经典猪瘟（CSF）疫情的延长与猪瘟病毒（CSFV）在野猪种群中的持续存在和广泛传播高度相关。为了调查野猪中CSF疫情的动态，进行了时空分析。2019年3月至6月，野猪中CSFV的阳性率波动剧烈，但最终稳定在约10%。自最初疫情爆发以来，从最初报告CSF的农场到当日最远感染野猪的欧几里得距离除群马县和埼玉县报告的病例外，随时间不断增加。使用积分嵌套拉普拉斯近似估计的两个月患病率在2019年3月至4月的一半感染区域达到>80%。尽管到2019年10月期间患病率下降，但受影响区域仍在继续扩大。纳入或排除群马县和埼玉县病例时，标准差椭圆的形状及其质心位置存在很大差异，这表明那里的感染不太可能仅仅由野猪活动引起，可能涉及人为因素。2019年7月后这些地区出现并发时空聚集表明此时CSF疫情已分散。这项流行病学分析的结果有助于解释CSF传播的动态，并将有助于实施包括诱饵疫苗接种在内的控制措施。
