Effect of Water Depth on the Infection of <i>Biomphalaria glabrata</i> by Miracidia of St. Lucian <i>Schistosoma mansoni</i> under Laboratory and Field Conditions

1. Laboratory and field trials were carried out to investigate the influence of depth on the infection of B. glabrata by St. Lucian S. mansoni miracidia. 2. In both laboratory and field experiments, miracidia located and infected snails to a depth of 122 cm. 3. The degree of infection seems to be related to the size of a habitat and its water volume. 4. Infection rates were high at the miracidial point of entry where miracidium-snail interaction was maximum and at the water surface where miracidia eventually congregated.