Schistosoma mansoni: effect of aestivation on the intra-molluscan stages and the survival rate of infected Biomphalaria pfeifferi

Abstract

Following exposure to the miracidia of Schistosoma mansoni, Biomphalaria pfeifferi were induced to aestivate immediately ('0 h') or on days 7, 14 or 21 post-infection and then re-activated at various times. The proportions of snails found to be alive at weekly intervals after re-activation were found to be related to the length of time the snails had spent between infection and aestivation (I-A), varying from 100% (0 h) to 5% (21 days). The mean numbers of cercariae produced by the snails after re-activation also varied with I-A, being highest in those that aestivated immediately post-infection, and cercarial development was delayed by prolonged desiccation of the infected snails, the intra-molluscan development of S. mansoni is affected by the aestivation of the snail host.