Landscape elements affecting the ingestion of oral vaccine against classical swine fever in wild boar

Classical swine fever (CSF) has been widespread among wild boars in Japan since the first outbreak in September 2018 after 26 years of absence. Although oral vaccination against CSF has been implemented, CSF infections are ongoing in the wild boar population. Therefore, increasing the effectiveness of oral vaccination in wild boars by distributing the vaccine in an environment where wild boars are likely to ingest the vaccine is necessary. This study aimed to investigate the landscape elements that facilitate the uptake of oral vaccines by wild boars. We used data from the oral vaccine campaign in Gunma and Tochigi prefectures in eastern Japan and analyzed the vaccine uptake rate and landscape structure at the vaccine distribution sites in two seasons. The uptake rate of the oral vaccine was significantly higher in the first season (Gunma: 41.5%, Tochigi: 37.1%) than in the second season (Gunma: 28.5%, Tochigi: 25.7%). We also found that broadleaf forest and bamboo woodland were negatively associated with vaccine uptake in Gumma Prefecture in the first and second seasons, respectively. These results indicate that vaccine uptake may be influenced by seasonal changes in wild boar food resources. Moreover, the results suggest that the uptake of oral vaccination may increase in environments with high landscape diversity, i.e., forest edge environments, which contain mainly forest elements and a small amount of cultivated land and city areas, whereas it may decrease in environments with mainly cultivated land and city areas and less forest elements due to the influence of human activities.

Automated summary

Classical swine fever has spread widely among wild boars in Japan, and despite the implementation of oral vaccination, infections are still ongoing. This study investigates the landscape elements that influence the uptake of oral vaccines by wild boars. The results indicate that seasonal changes and landscape diversity can affect vaccine uptake.