Simple Summary
Since 2014, Lithuania has been affected by African swine fever (ASF), with varying levels of disease occurrence across regions. This study aimed to identify factors associated with the persistence of ASF in wild boar populations at the municipality level. Municipalities were classified as endemic, non-endemic, or with no ASF detected, based on whether the disease was detected for at least three consecutive years. The analysis covered the period from 2016 to 2022 and identified differences in ASF occurrence between municipality groups. The number of hunted wild boar did not differ significantly between groups, suggesting that hunting numbers alone were not sufficient to explain differences in disease occurrence. The high proportion of ASF-positive animals among found dead wild boar supported the importance of carcass detections and passive surveillance for identifying areas with ongoing virus circulation. Environmental factors were also associated with ASF detection patterns. Higher forest cover was linked to fewer detected ASF cases, whereas wetland areas were associated with a higher probability of ASF occurrence. These findings suggest that environmental conditions may contribute to virus persistence. Overall, this study supports targeted surveillance, including carcass search, and indicates that environmental conditions should be considered when managing ASF in wild boar populations.
Abstract
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.