Schistosoma haematobium: comparative studies on the characteristics of infection in three populations of Planorbarius metidjensis from the Agadir province in South Morocco.

Planorbarius metidjensis measuring 2 or 3 mm in diameter and originating from three populations in the Agadir province (Ida Ou Gnidif, Imouzzer, and Sidi Belkacem) were experimentally infected with Schistosoma haematobium to determine if the complete larval development of the parasite might be ensured by any snail population of the Agadir province and to compare the general characteristics of infection. No significant difference between the three populations was noted in the survival rates of snails when the first shedding occurred or in the prevalence of infection. The mean duration of the shedding period was significantly higher in the Imouzzer population (111 days versus 53-58 days). The total number of cercariae shed per mollusc was significantly lower in the Ida Ou Gnidif planorbids (1,398/snail versus 3,346 and 3,343/snail in the other 2 groups). The same rhythm in daily cercarial production was noted in the three snail groups, with the periodicity being 18-20 days. Despite some differences in parasite development between the three snail populations, the different populations of P. metidjensis can ensure the complete development of S. haematobium and maintain local transmission in the South of Morocco.