Forest Density and Invasive Carnivores Are Related to Trichinella Infection in Wild Boars in Poland

The purpose of this study was to investigate and update the spatial distribution of Trichinella spp. in wild boars tested between 2015 and 2022 and to test the correlation of the population density of chosen animals (wild boars, red foxes (Vulpes vulpes), raccoon dogs (Nyctereutes procyonoides), and European badgers (Meles meles)) with the prevalence of Trichinella spp. in wild boars in Poland. In addition, to understand the distribution of infected animals, we sought to see if there were a correlation of Trichinella spp. infections in wild boars with land cover type. Among the wild carnivore species analyzed, only the population density of the raccoon dog (Nyctereutes procyonoides)-an invasive alien species-was significantly associated with infection rates in wild boars, particularly at the regional scale. As scavengers and competent reservoir hosts for all four European Trichinella species, raccoon dogs are likely to play a key role in the sylvatic transmission cycle. The positive rate of Trichinella spp. infection in wild boars during 2015-2022 was 0.22%, compared to 0.3% in 2009-2016. Moreover, forest density was positively correlated with infection rates, underlining the role of forest habitats in sustaining Trichinella transmission.