Environmental Factors Associated with African Swine Fever Persistence in Wild Boar Populations in Lithuania

Since 2014, Lithuania has been affected by African swine fever (ASF), with varying levels of disease occurrence. This study investigated factors associated with ASF persistence in wild boar populations across Lithuanian municipalities. Based on ASF occurrence patterns, municipalities were classified into three groups: endemic, non-endemic, and ‘no ASF detected’. Endemic municipalities had ASF cases reported for at least three consecutive years. Data from 2016 to 2022 were analysed, including numbers of wild boar hunted or found dead, environmental variables, and spatial characteristics. Analyses included non-parametric tests, correlation analyses, negative binomial regression, and longitudinal logistic regression using generalised estimating equations to assess associations with ASF occurrence. Differences were observed between municipality groups, with endemic areas showing higher numbers of ASF cases and found dead wild boar. The number of hunted wild boar was positively correlated with the number of ASF-positive hunted wild boar, likely reflecting hunting-related sampling effort. Forest cover was negatively associated with ASF case counts, while wetland coverage was positively associated with endemic status, case counts and ASF presence over time. The findings highlight the importance of surveillance strategies, especially those based on carcass detection and testing. Environmental factors, including wetland-associated conditions, may influence ASF occurrence. Results support the need for targeted, landscape-informed approaches to ASF surveillance and control in endemic regions.