Effect of a short period of desiccation during the patent period on cercarial shedding of Schistosoma haematobium from Planorbarius metidjensis.

Planorbarius metidjensis infected with Schistosoma haematobium were subjected, from the first day of shedding, to a 5- or 10-day period of desiccation in order to study its effect on the cercarial release occurring after reactivation of snails in water. These results were compared to those of infected controls that were not subjected to desiccation. Compared to controls, the duration of shedding following reactivation was shorter and the total number of cercariae shed by each infected snail was smaller in the 5- and 10-day groups. The rhythm occurring in the daily cercarial production of the 5-day group was shorter (11 days only) at the beginning of the shedding period and lengthened to 17-18 days at the end of the patent period. In the 10-day group, no rhythm was found. These results could be explained by the length of the desiccation period and its consequences on the development of S. haematobiumsporocysts in the body of snails.