Trichinella in the North

Background Endemic human trichinellosis has been rare in Norway, Sweden and Finland. In Norway the last outbreak involving five persons is from 1953 and before that there were reported six epidemics with 711 patients since 1881 (reference in [1]). In Sweden 10 outbreaks involving 504 patients were documented 1917-1969 (reference in [2]). In Finland only eight human cases have been reported since 1890, the latest being three hunters at 1977 who got the infection from bear meat (reference in [1]). Sporadic cases of trichinellosis in production animals have been detected in pig meat inspection in these countries. In Norway there was a peak of positive pigs in the 1950’s and 1960’s but since 1981 no positive finding in pigs has been reported. In Sweden, 127 positive pigs were reported 1970-1999 and no cases since 2000. The first infected Finnish pig was found 1954, and the total number of positive pigs in fifty years was up to 714 (1954-2003). There was a peak of cases in the 1980’s and 90’s when a total of 671 pigs were found positive. During 1981-2000, the positive animals originated from 0-19 farms yearly. Since 2004 no trichinella has been found in pigs. The decrease in Trichinella prevalence and incidence in domestic swine has been speculated to be due the change in Finnish swine industry since Finland joined the EU in 1995 [3]. During recent years, the industry has moved towards large-scale enterprises with corporative ownership with new facilities. These are better protected against the Trichinella infection commonly present in surrounding wildlife in Finland [3]. High sylvatic trichinellosis prevalence has been reflected to farmed wild boars in which condemnation due trichinelllosis has been relatively more common than in pig. To clarify the spatial variation of sylvatic trichinella prevalence suggested in earlier studies, a new Finnish sample set was analyzed.