Food-Borne Helminthiases

Abstract

A substantial number of heteroxenous helminth species that live in man as parasites are programmed to complete their development to the stage of infective larvae in animals or on plants which are used as foodstuffs for man. However, a human infection can only take place, if such animals or plants are consumed in a raw or insufficiently cooked (i.e. heated) state. Apart from geofactors affecting the helminth larvae when free-living as well as during the developmental period in the intermediate hosts, it is above all the feeding habits of the people themselves — specific to every region — which determine the geographical distribution of these helminthic infections. In every case in which man functions as the sole final host his defecation habits, too, are of great significance for the persistence of food-borne helminthiases. This is because an appropriate contamination of the intermediate host’s milieu alone enables the parasite cycle to continue. In euryxenous helminths with a broad spectrum of final hosts on the other hand, this factor does not play a role: the final animal host then contaminates the intermediate host’s milieu.