Effect of Helisoma duryi on the survival, growth, and cercarial production of Schistosoma mansoni-infected Biomphalaria glabrata.

Biological control of the intermediate hosts of S. mansoni and S. haematobium by means of a competitor snail,Helisoma duryi, has been suggested. In the present laboratory study, information was obtained concerning the interspecific competition between H. duryi and B. glabrata. The results indicated that the growth rate, mortality rate, and cercarial production of S. mansoni-infected B. glabrata were highly influenced by H. duryi. These observations agree with results obtained in earlier experiments concerning the interspecific competition between H. duryi and S. mansoni-infected B. pfeifferi. The exact characteristics of the influencing factor have not yet been determined, but the observations indicated that H. duryi could possibly be used as a biological control agent.