A COMPARATIVE-STUDY OF THE SHEDDING OF CERCARIAE OF SCHISTOSOMA-HAEMATOBIUM IN NEWBORN BULINUS-TRUNCATUS

A comparative study of the shedding of cercariae of Schistosoma haemat obium was performed in Bulinus truncatus and Planorbarius metidjensis individually exposed to 5 miracidia in their first 72 h of life. No si gnificant difference was noted between the mean values of the two snai l groups concerning the prepatent period duration (53-57 days at 24 de grees-26 degrees C), the patent period duration (41 days for B. trunca tus, 70 days for P. metidjensis), or the total number of cercariae (1, 499 per B. truncatus, 1,935 per P. metidjensis). Successive periods o f heavy and low production were encountered in the shedding of cercari ae; however, the periodicity was identical in the two snail species (2 5-27 days) and the emergence of cercariae peaked between 11 a.m. and 1 p. m.