Host-parasite Relationships ofBulinus globosusandB. truncatuswith Strains ofSchistosoma haematobiutm

Abstract

It is apparent that under the conditions of the observations recorded in this study the host-parasite relationships of the two species of snails and their respective strains ofS. haematobiumexhibit marked similarity in certain respects but differ in others. Higher cercarial infection rates were obtained inB. globosusthan inB. truncalusat relatively low miracidial exposure levels but the daily mean cercarial outputs of each species at the same miracidial exposure level were similar. A higher frequency of production of large numbers of cercariae was recorded for infividualB. globosusthan forB. truncatus. The mean cercarial prepatent periods forB. globosusandB. truncatusat a level of 7 miracidia were each 32 days, but infectedB. globosuslived appreciably longer than infectedB. truncatus. The hourly output of both species exposed to stimuli for the same period of time was broadly similar. Peaks of cercarial production were generally reached earlier by individualB. truncatus(2 weeks) after onset of shedding than by individualB. globosus(4–5 weeks), although erratic shedding was observed for both species.