Wild boar at the farm gate: infectious diseases and epidemiology at the wildlife-livestock interface

The wildlife-livestock interface is a complex system shaped by various factors including hosts, pathogens and possible transmission routes of infections. The global spread of African swine fever (ASF) and the detection of Salmonella Choleraesuis in wild boar highlight the need to understand potential contacts between wild boar and domestic pigs in Sweden. ASF, a viral disease affecting pigs and wild boars, has a case fatality rate of up to 100% and can remain infectious in carcasses for extended periods. S. Choleraesuis may cause systemic disease with pneumonia, sepsis and mortality in both pigs and wild boar alike. Although these two diseases are caused by distinctly different pathogens, they share certain epidemiological features which can be used when conducting surveillance.A survey of Swedish pig producers found that 80% had noted wild boar or wild boar activity near their farms within the past year, with one-third reported more frequent encounters. Almost two-thirds reported crop damage from wild boars. Perimeter fences were rare, and common wild boar deterrents included hunting and strategic baiting. Hunters expressed willingness to participate in ASF surveillance and control, emphasizing the need for practical reporting systems. Baiting was common, with maize and cereals as typical feeds, but the use of imported maize had decreased. National surveillance of Salmonella in wild boar was initiated, as S. Choleraesuis is seen in dense populations in the eastern and southern parts of Sweden. In summary, the proximity of wild boar to pig farms poses a risk of disease transmission, necessitating surveillance and biosecurity measures. Collaboration with hunters and an understanding of local dynamics contribute to preventing the spread of infections.