Impact of the freshwater operculate snail Melanoides tuberculata on Survival and Egg Production of the planorbid snail Bulinus truncates and on its transmission of Schistosoma haematobium Infection

The biological control of vector snails is an essential component in the fight against schistosomiasis. Melanoides tuberculata (Thiaridae: Prosobranchia) was evaluated experimentally for its impact on the survival, egg production, of Bulinus truncatus, and its infection rate and cercarial production of Schistosoma haematobium. M. tuberculata has been proved to have a considerably negative effect on the survival and egg production of B. truncatus. The results show also that this suppressive effect becomes much higher as the relative density of Melanoides to Bulinus snails was increased. Besides, this was associated with considerable decline of Bulinus egg production. The rate of infection of Bulinus snails with S. haematobium was found to be significantly reduced by the presence of Melanoides during miracidial exposure of snails. The same was also observed if Melanoides was maintained with miracidially exposed Bulinus throughout its life span. The rate of infection of Bulinus with S. haematobium and the cercarial production was much reduced in comparison with the control group and therefore the total periodic cercarial production was reduced by 78.2%. The effects of Melanoides are additive and thus could lead to considerable depression in schistosomiasis transmission. This supports the utilization of Melanoides in the biocontrol of schistosomiasis in Egypt.