RESUMO
Biomphalaria alexandrina snails, intermediate hosts of Schistosoma mansoni either native or exposed, were treated with praziquantel or subjected to UV- and gamma-irradiation. The hemocytes count in native snails with different sizes was compared with the hemocytes count in exposed snails at different intervals post exposure. As well, the humoral response of plasma from native and exposed snails was measured by direct hemagglutination assay. The obtained results indicated high significant interrelations between different experimental treatments, non-treated control and different time intervals of the experiment for both native and exposed snails. The interaction between different snail sizes [native] and the experimental treatments was also highly significant, whereas, no significant interaction was observed between the experimental treatments of the exposed snails and the hemocytes count at different intervals post exposure. The hemocytes count of both UV- and gamma-irradiated snails showed slight decrease as compared with the control for both native and exposed snails. Meanwhile, snails treated with praziquantel showed relative increase in hemocytes count in both native and exposed snails as compared with control, UV- and gamma-Irradiated snails. The observed hemagglutination titre of plasma from either native or exposed snails was not considerably changed in all the experimental groups throughout the course of the experiment. It is concluded that the chemical treatment with praziquantel enhance the immune response in both native and exposed B. alexandrina snails, which could affect the development of the infective larvae inside the snails to a great extent. So, praziquantel could be recommended as a potent molluscicidal and larvicidal agent than UV-and gamma-Irradiation