Diversity of Trichinella species in relation to the host species and geographical location.

Trichinella nematodes still circulate in various hosts in both domestic and sylvatic environments. Recently, in Europe, the transmission of Trichinella spp. to humans has been attributed more to wild animals than to domestic animals. However, domestic animals could still be a source of human infections in some regions. Therefore, our aim was to determine the species composition of Trichinella and the prevalence and intensity of infections in animal populations from the domestic cycle, namely pigs (Sus scrofa f. domestica); the synantropic cycle, in the form of rats (Rattus norvegicus); and the sylvatic cycle, namely wild boars (Sus scrofa) and red foxes (Vulpes vulpes), in Poland. The findings showed that the nematode prevalence in pigs (0.0002 %) and wild boars (0.3 %) was lower than it was in red foxes (4 %). A very high prevalence was found in rats (23.3 %), but it must be emphasized that the investigated rat samples were collected from farms where pigs were infected with Trichinella spp. The mean larval burden was found to be higher in wild boars and pigs (11.48 lpg and 10.19 lpg) than in red foxes and rats (4.09 and 2.30). Trichinella spiralis was the predominant species in pigs (98.6 %), wild boars (77.3 %) and rats (100 %), while in red foxes, this species occurred less frequently (15.5 %). The most frequently occurring species in red foxes was Trichinella britovi (73.2 %). Moreover, in wild boar and red fox coinfections, T. spiralis/T. britovi were detected (3.1 and 9.9 %, respectively). In addition, Trichinella pseudospiralis was detected in a few wild boars (0.5 %) and Trichinella nativa was found in one red fox and one wild boar. Furthermore, different T. spiralis and T. britovi prevalence ratios in various geographical regions were found. In the wild boar population, a higher frequency of T. spiralis (70-85 % of infected animals) was observed in the western and central parts of Poland, while in the eastern part, this dominance was not as evident (46-59 %). In the red fox population, T. britovi was abundant throughout the entire territory; however, its highest prevalence was in the east (90-100 %).