Epidemiological analyses of the 2010 foot-and-mouth disease epidemic in Japan

A large-scale foot-and-mouth disease (FMD) epidemic occurred in Japan in 2010. During the epidemic, the emergency vaccination strategy was conducted for the first time in Japan. Ultimately, this epidemic was contained within 3 months, and then led a total of 292 detected farms and nearly 290,000 culled animals including vaccinated animals. Such a large-scale epidemic of FMD has never experienced in Japan, and it caused severe damage to the local livestock industry and related industries. In this article, some epidemiological analyses of the FMD epidemic are introduced. First, descriptive and spatial analyses were conducted to understand the character of the epidemic. The epidemic was primarily localized within 20km of the north-south area of Miyazaki Prefecture. The epidemic area features a densely populated livestock area even in Miyazaki, which has been known as one of the major livestock farming regeion in Japan. A spatial clustering of the disease was detected by the spatial analysis and this cluster was located in an area more densely populated with both cattle and pig. This implies that high density of livestock animals was a crucial aspetc of the epidemic and pig farms played an important role to induce the dissemination of the disase in the area. Next, a case-control study was conducted to investigate the risk factors associated with FMD transmission under the movement restriction. This study resulted that in the highly affected area the disease was likely to spread regardless of the movements of people and vehicles, and physical barriers around barns such as walls or clumps of trees were found to be a protective factor. Meanwhile, in the less affected area movements of people and vehicles was strongly associated with the disease spread. Lastly, an FMD transmission model was developed using the epidemic data to evaluate the effects of several control measures. The transmission model demonstrated that prompt culling on infected farms or early detection of an index case could contribute effective and efficient prevention of the disease spread in the epidemic area. As an optional strategy, preemptive culling demonstrated good effectiveness in reduction of the number of infected farms. However, applying this strategy in the densely populated areas may have practical difficulties because it required a large amount of resources. The vaccination strategy with the wide range in the early phase of the epidemic also showed the potential to contain the epidemic on a small scale, but vaccination strategy posed some difficulties in management of vaccinated animals whether they are culled or not.