Effects of Some Physico-chemical Factors on the Infection of Biomphalaria glabrata (Say) by Miracidia of Schistosoma mansoni Sambon in St. Lucia, West Indies

Abstract

1. The four physico-chemical characteristics of water tested— volume, salinity, pH, and turbidity—were each found to affect infection of B. glabrata by S. mansoni miracidia. 2. The rate of infection decreased as the water volume increased from 90·6% at 0·005 litre to 47·5% at 50 litres. 3. The rate of infection decreased as sodium chloride concentration increased, from 78·7% at 0·5 ppm to 2·1% at 4200 ppm. Above 4200 ppm no infection occurred. The activity of the miracidia was affected above 1200 ppm. The snails became non-motile at above 4800 ppm and died within 10 hours at higher concentrations.