SCHISTOSOMA HAEMATOBOIUM - COMPARATIVE-STUDIES ON PREVALENCE AND CERCARIAL SHEDDING ACCORDING TO THE SHELL DIAMETER OF PLANORBARIUS0-METIDJENSIS AT MIRACIDIAL EXPOSURE

Experimental infections of Planorbarius metidjensis by Schistosoma hae matobium were carried out under controlled conditions to determine whe ther there was a size limit after which the snail could not longer sus tain Schistosoma infection. Snails measuring 1-6 mm in diameter were e xposed to two miracidia each and were raised at 24-26 degrees C until their death. The frequency of snails with cercarial shedding was 63% i n the 2.1- to 3-mm group. In the other groups the frequencies were low er, decreasing to 2.8% in the 5.1- to 6- mm group. The periodicity of S. haematobium cercarial shedding was not modified by the snail diamet er at miracidial exposure.