Environmental and human influence on the ecology ofTrichinella spiralisandTrichinella britoviin Western Europe

Abstract

SUMMARYSurveys onTrichinellaparasites in domestic and sylvatic animals collected in France, Italy, and in the Extremadura region of Spain showed that the distribution ofTrichinella spiralisandTrichinella britoviis influenced by both environmental and human behaviour factors. In France, bothTrichinellaspecies are prevalent in the fox population from mountain areas and natural parks but are infrequent in wild boars (< 0·001%). In Italy, onlyT. britoviis present in sylvatic animals (foxes, wolves, and mustelids) living 500 m above sea level. This species is rare in wild boars ( < 0·001%) in that area. Sylvatic trichinellosis is found in only 24% and 34% of French and Italian territory, respectively, while lowland areas may generally be consideredTrichinella-free, because the domestic cycle is absent. The ecology ofT. spiralisandT. britoviin 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 maintenance ofT. spiralisin the domestic environment, but it also has a great impact on the prevalence in wild boar populations. It does not influence the prevalence in vulpine populations. These data suggest (1) that domestic trichinellosis occurs only in rural areas of Western Europe in association with traditional swine-rearing practices, but not in industrialized pig farms; (2) that sylvatic trichinellosis occurs only in natural habitats which, in Western Europe, are widespread in mountain areas; (3) that the fox is the primary reservoir in the sylvatic cycle, where the parasite is maintained in a closed circuit and (4) that among sylvatic animalsT. spiralisis present at lower altitude than isT. britovi.