Host-parasite relationships of cercariae of Trichobilharzia stagnicolae.

Abstract

Survival of cercariae of Trichobilharzia stagnicolae from naturally infected Stagnicola emarginata was determined at several different temperatures: 6, 17.5, 22, 27.5, and 32.5 C. Cercarial longevity appeared to be inversely related to temperature, as cercariae lived for only 18 hours at 32.5 C and lived more than 80 hours at 6 C. The effect of cercarial age on papule formation was evaluated by exposing seven human subjects to cercariae of three different ages: 0, 9, and 24 hours old. Despite differences in responses among the seven human subjects, cercarial age did not significantly affect the proportion of size of papules resulting from exposure. In each case, 43-57% of the cercariae resulted in papules.