The effect of exposure to selected numbers of Schistosoma mansoni miracidia on survival of cohorts of Biomphalaria pfeifferi

Abstract

Cohorts of 25 specimens of Biomphalaria pfeifferi were each exposed to batches of one, three, five, seven and 10 Schistosoma mansoni miracidia per snail. The effect on survival was evaluated by calculating the weekly per capita mortality rates and the mean life expectancy of the exposed snails. No statistically significant difference could be demonstrated between the mean per capita mortality rates of cohorts exposed to one and three miracidia per snail. Likewise there was no significant difference between the values obtained for cohorts exposed to five, seven and 10 miracidia per snail. In general, however, survival of the cohorts showed an inverse relationship with the number of miracidia to which each individual snail was exposed.