澤井 宏太郎

In Japan, outbreaks of H5N8 highly pathogenic avian influenza (HPAI) were reported between November 2020 and March 2021 in 52 poultry farms. Understanding HPAI epidemiology would help poultry industries improve their awareness of the disease and enhance the immediate implementation of biosecurity measures. This study was a simulation-based matched case-control study to elucidate the risk factors associated with HPAI outbreaks in chicken farms in Japan. Data were collected from 42 HPAI-affected farms and 463 control farms that were within a 5-km radius of each case farm but remained uninfected. When infected farms were detected as clusters, one farm was randomly selected from each cluster, considering the possibility that the cluster was formed by farm-to-farm transmission within an epidemic area. For each case farm, up to three control farms were selected within a 5-km radius. Overall, 26 case farms (16 layer and 10 broiler farms) and 75 control farms (45 layer and 30 broiler farms) were resampled 1000 times for the conditional logistic regression model with explanatory variables comprising geographical factors and farm flock size. A larger flock size and shorter distance to water bodies from the farm were found to increase infection risk in layer farms. Similarly, in broiler farms, a shorter distance to water bodies increased infection risk. On larger farms, frequent access of farm staff and instrument carriages to premises could lead to increased infection risk. Waterfowl visiting water bodies around farms may also be associated with infection risk.

Geographical wildlife patterns reflect historical range expansion and connectivity and provide insights into wildlife population management. In our large-scale phylogeographic population analysis of wild boars (Sus scrofa leucomystax) in Japan, we identified 15 clusters using 29 microsatellite markers, each structured within a range of approximately 200 km. This suggests that evolution was essentially driven by isolation by distance, and that the range of gene flow was limited. One cluster contained subpopulations located approximately 900 km apart, indicating the occurrence of past anthropogenic introductions. Moreover, we estimated effective migration to visualize the geographic genetic population diversity. This analysis identified six potential barriers, one of which involved large plains and mountainous areas in the Kanto region of eastern Japan. This barrier likely persisted in the two eastern clusters for an extended period, restricting migration to the neighboring areas. Overall, our study sheds light on the demographic history of wild boar in Japan, provides evidence of past anthropogenic introductions from distant areas, and highlights the importance of geographic barriers in shaping genetic diversity and population dynamics. This knowledge will be beneficial for forming informed wildlife management strategies toward the conservation of genetic integrity and ecological balance of wild boar populations in Japan.

Classical swine fever (CSF) re-emerged in Gifu Prefecture, central Japan, in September 2018 and is currently widespread in wild boar populations. Due to its widespread in wild boars, an oral mass vaccination strategy was initiated in March 2019, employing a commercial bait vaccine that is a live attenuated vaccine. To enhance the effectiveness of oral vaccination, it is crucial to determine the vaccine's effective spatial range. This understanding is essential for devising a comprehensive vaccination strategy, which should also include a preliminary investigation of wild boar habitats before vaccination. This study aimed to estimate the effective range of oral vaccination for wild boars against CSF by analyzing the geographical relationship between immune wild boars and vaccination points within the vaccination areas in Gifu Prefecture. This study utilized oral vaccination data from April 2021 to March 2022. The prevalence of CSF infections in wild boars remained below 5% in this period, suggesting limited disease transmission and immune wild boars were considered to be induced by the effect of vaccination. Two vaccination campaigns were conducted during this period, with almost 2000 vaccination points each. To investigate the factors associated with the intensity (i.e., density) of immune wild boar, the nearest distances to a vaccination point and to a susceptible wild boar were evaluated as explanatory variables. The Rhohat procedure and point process model were utilized to analyze the relationship between the intensity of immune wild boars and the explanatory variables. The point process model revealed a significant decrease in the intensity of immune wild boars when the distance from the nearest vaccination point exceeded 500 m, indicating that the effective spatial range of bait vaccination is within 500 m of the vaccination point. Although the distance to the nearest susceptible animal did not show significance in the model, Rhohat plots indicated that the intensity of immune wild boars decreased at distances greater than 1200 m from the nearest susceptible wild boar. This finding highlights the importance of investigating susceptible wild boar populations within a range of at least 1200 m from a vaccination point before implementation. The present study revealed the effective range of oral vaccination for wild boars against CSF and indicated the importance of investigating susceptible wild boar habitats around vaccination points before the implementation of vaccination. These findings may help improve the effectiveness of oral vaccinations.

OBJECTIVES: Animal movement is an important factor in the transmission of infectious diseases among livestock. A better understanding of animal movement characteristics provides a more reliable estimation of disease spread and promotes modeling studies. In Japan, all the cattle movement information is recorded in a national database called the Individual Cattle Identification Register (ICIR)." Our previous studies using this information demonstrated heterogeneity in the movement of dairy and beef cows according to location, season, and age. The present study describes the probability distributions of the movement of Japanese dairy and beef cows in the following month on a regional basis. DATA DESCRIPTION: This publication contains four probability distribution datasets for the predicted locations of dairy and beef cows in Japan in the following month, which were developed using individual cattle movement information obtained from the ICIR. These datasets provide information on cattle movement in the following month on a regional basis, given properties such as birth region, location, time, and age.

The COVID-19 pandemic has highlighted the importance of the One Health (OH) approach, which considers the health of humans, animals, and the environment in preventing future pandemics. A wide range of sustainable interdisciplinary collaborations are required to truly fulfill the purpose of the OH approach. It is well-recognized, however, that such collaborations are challenging. In this study, we undertook key-informant interviews with a panel of stakeholders from Japan to identify their perceived needs and challenges related to OH research. This panel included scientists, government officials, journalists, and industry stakeholders. By combining a thematic analysis of these interviews and a literature review, we summarized two key themes pertinent to the effective implementation of OH research: types of required research and systems to support that research. As a technological issue, interviewees suggested the importance of research and development of methodologies that can promote the integration and collaboration of research fields that are currently fragmented. An example of such a methodology would allow researchers to obtain high-resolution metadata (e.g. ecological and wildlife data) with high throughput and then maximize the use of the obtained metadata in research, such as in environmental DNA analysis, database construction, or the use of computational algorithms to find novel viral genomes. In terms of systems surrounding OH research, some interviewees stressed the importance of creating a sustainable research system, such as one that has continuous budget support and allows researchers to pursue their academic careers and interests. These perceptions and challenges held by Japanese stakeholders may be common to others around the world. We hope this review will encourage more researchers and others to work together to create a resilient society against future pandemics.