[The modification of Helicella obvia by Dicrocoelium parthenitae].

During the pasture period in 1990 the snail species Helicella obvia, collected in a dicrocoeliosis area in the east of Brandenburg, was investigated for Dicrocoelium sporocysts. Simultaneously in adult snails the condition of albumen gland was examined. Investigations showed that Dicrocoelium infection in the snail host impairs their reproduction ability and life expectancy. The term "parasite caused sterilisation" is suggested for changes which lead to infertility in the case of parasite infection.