ABSTRACT
The susceptibility of Biomphalaria alexandrina, Biomphalaria glabrata and a hybrid snail of both, all obtained from natural habitats in Egypt, to infection with six human local strains of Schistosoma mansoni and a laboratory strain of human origin was determined. The infection rate, prepatent period, periodic cercarial production and duration of cercarial shedding were compared in all cases. The results showed that each of the three studied Biomphalaria snails had different rates of infection and different values of total periodic cercarial production with various strains of S. mansoni. However, the mean infection rate of all local S. mansoni strains was significantly much higher in B. alexandrina than each of B. glabrata and the hybrid snail, being 66%, 7.2% and 8.5%, respectively. Considering the mean of results of all local S. mansoni strains used, the longevity of cercariae-shedding B. glabrata and the hybrid snails was much longer than that of B. alexandrina, with high significant difference between them (P < 0.01), being 94.5, 103.3 & 69.1 days, respectively. The mean prepatent period of various S. mansoni strains showed no significant difference in the three Biomphalaria snails studied. The hybrid snail produced periodically (1 h stimulant twice weekly) more schistosome cercariae/snail (4,784.2) than B. glabrata (2,913.4 cercariae/snail) and the least production was in the case of B. alexandrina (1,397.2 cercariae/snail) (P < 0.05). The diurnal pattern of S. mansoni cercarial shedding was found to be similar for B. glabrata, B. alexandrina and the hybrid snail showing a peak of cercariae at the same time (9-10 a.m.).
