Division of Transboundary Animal Disease Research, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan.
Division of Transboundary Animal Disease Research, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan.
Prev Vet Med. 2022 Jan;198:105554. doi: 10.1016/j.prevetmed.2021.105554. Epub 2021 Dec 1.
In 2018, classical swine fever (CSF) re-emerged in the Gifu Prefecture, central Japan, causing an on-going outbreak among wild boars and domestic pigs in the country. Consequently, oral vaccination for wild boar and compulsory vaccination for pig farms started in 2019. We have previously shown that, before vaccination in the Gifu Prefecture, the presence of CSF-infected wild boar near pig farms increased the risk of CSF transmission. This study aimed to re-evaluate the transmission risk from wild boars to pig farms under a vaccination program. The effectiveness of vaccination was evaluated by comparing the transmission risk estimated before and after the implementation of vaccinations. In this study, we focused on two affected areas, the Kanto (eastern Japan) and Kinki (west-central Japan) regions, in which eight of 11 infected farms were detected between the start of pig farm vaccinations and April 2021. Wild boar surveillance data from an area within a 50-km radius from the infected farms were used for analysis, consisting of 18,870 1-km grid cells (207 infected cells) in the Kanto region, and 15,677 cells (417 infected cells) in the Kinki region. The transmission rates in the post-vaccination period in the Kanto and Kinki regions were much lower than that in the pre-vaccination period in the Gifu Prefecture. The values of transmission kernels (h, transmission rate at 0 km) in the Kanto and Kinki regions decreased to 1% of the transmission kernel in the pre-vaccination period. In the pre-vaccination period, the risk of infection within 300 days was almost 95 % when one infected grid cell was detected within 1 km of a pig farm. Meanwhile, in the post-vaccination period, the risk of infection within 300 days was approximately 5% when several infected cells were detected within 1 km of a pig farm. Considering the limited effect of oral vaccination for wild boar due to distribution limitations in the Kanto and Kinki regions, vaccination on pig farms may seems to have mainly reduced the transmission risk from wild boar. However, despite the implementation of vaccination, the risk of infection on pig farms remains present due to the immunity gap of weaning pigs. Therefore, strict biosecurity measures on pig farms and an appropriate vaccination program are required to prevent and control CSF spread.
2018 年，古典猪瘟（CSF）在日本中部岐阜县再次出现，导致该国野猪和家猪持续爆发疫情。因此，2019 年开始对野猪进行口服疫苗接种和对养猪场进行强制疫苗接种。我们之前曾表明，在岐阜县接种疫苗之前，在养猪场附近发现感染 CSF 的野猪会增加 CSF 传播的风险。本研究旨在评估在接种疫苗计划下，野猪向养猪场传播的风险。通过比较接种前后估计的传播风险来评估疫苗的有效性。在这项研究中，我们关注了两个受影响的地区，即关东（日本东部）和近畿（日本中西部）地区，在这两个地区，在开始对养猪场进行疫苗接种和 2021 年 4 月之间，发现了 11 个感染农场中有 8 个农场感染。使用来自距感染农场 50 公里半径范围内的一个地区的野猪监测数据进行分析，该地区在关东地区包括 18870 个 1 公里网格单元（207 个感染单元），在近畿地区包括 15677 个单元（417 个感染单元）。在关东和近畿地区的接种后时期，传播率远低于岐阜县的接种前时期。关东和近畿地区的传播核（h，在 0 公里处的传播率）值下降到接种前时期的 1%。在接种前时期，当在养猪场 1 公里范围内检测到一个感染网格单元时，在 300 天内感染的风险几乎为 95%。而在接种后时期，当在养猪场 1 公里范围内检测到几个感染单元时，在 300 天内感染的风险约为 5%。考虑到在关东和近畿地区由于分布限制，对野猪进行口服疫苗接种的效果有限，因此，养猪场的疫苗接种似乎主要降低了野猪传播的风险。然而，尽管实施了疫苗接种，但由于断奶猪的免疫空白，养猪场的感染风险仍然存在。因此，需要严格的养猪场生物安全措施和适当的疫苗接种计划，以预防和控制 CSF 的传播。
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