ENVIRONMENTAL AND HUMAN INFLUENCE ON THE ECOLOGY OF TRICHINELLA-SPIRALIS AND TRICHINELLA-BRITOVI IN WESTERN-EUROPE

Surveys on Trichinella parasites in domestic and sylvatic animals coll ected in France, Italy, and in the Extremadura region of Spain showed that the distribution of Trichinella spiralis and Trichinella britovi is influenced by both environmental and human behaviour factors. In Fr ance, both Trichinella species are prevalent in the fox population fro m mountain areas and natural parks but are infrequent in wild boars (< 0.001%). In Italy, only T. britovi is present in sylvatic animals (fo xes, wolves, and mustelids) living 500 m above sea level. This species is rare in wild boars (< 0.001%) in that area. Sylvatic trichinellosi s is found in only 24%, and 34% of French and Italian territory, respe ctively, while lowland areas may generally be considered Trichinella-f ree, because the domestic cycle is absent. The ecology of T. spiralis and T. britovi in the Extremadura shows a different picture from that observed in France and Italy because of the presence of both domestic and sylvatic cycles. The domestic cycle not only allows the maintenanc e of T. spiralis in the domestic environment, but it also has a great impact on the prevalence in wild boar populations. It does not influen ce the prevalence in vulpine populations. These data suggest (1) that domestic trichinellosis occurs only in rural areas of Western Europe i n association with traditional swine-rearing practices, but not in ind ustrialized pig farms; (2) that sylvatic trichinellosis occurs only in natural habitats which, in Western Europe, are widespread in mountain areas; (3) that the fos is the primary reservoir in the sylvatic cycl e, where the parasite is maintained in a closed circuit and (4) that a mong sylvatic animals T. spiralis is present at lower altitude than is T. britovi.