Synanthropic Trichinella infection in Finland

The first three human trichinellosis cases in Finland were recorded around 1890, and altogether eight cases were registered until 2008. The first infected Finnish swine was found in 1954. From the early 1980s, an increasing trend in the number of infected swine was seen, with the highest number registered in 1996, after which a decrease has been observed. Infected pigs were found yearly until 2004. Since 1954, all slaughtered pigs have been tested for Trichinella, regardless of subsequent export or domestic consumption purpose. All Trichinella infections revealed in pigs are, since 1998, analysed for species by multiplex PCR. So far, all larvae from pig infections have been identified as Trichinella spiralis. During the recent decreasing trend in prevalence, the number of pig farms has also decreased, while the yearly number of slaughtered pigs has remained stable or even slightly increased. For many decades, the Trichinella prevalence in Finnish wildlife has remained high. Foxes, raccoon dogs, wolves, and lynx in the southern part of the country exhibit prevalence exceeding 50%. The most common species in wildlife is Trichinella nativa, a species with very low infectivity to swine, but also, T. spiralis, Trichinella britovi, and Trichinella pseudospiralis occur in wildlife.