Assessment of the interaction between chemical and biological control of biomphalaria alexandrina: the intermediate host of schistosomiasis mansoni

ABSTRACT

The acute molluscicidal activity of bayluscide is 80-100 times more than that of lannate, against both the target snail, B. alexandrina, and the biocontrol snail, L. carinatus, which showed about twice sensitivity to the tested compounds. Prolonged exposure for 7 weeks to sublethal concentration of lannate or bayluscide [1/10 LC50] in the presence of the biocontrol agent changed water pH, although, the changes were still in the survival range of the target snail. However, pesticide treatments and biocontrol agent had an adding action on increasing the death rate of the target snail which was more susceptible to lannate than to bayluscide. The tested concentration of Lannate associated with the biocontrol agent, positively influenced the egg laying capacity of the target snail, while Bayluscide treatment decreased this capacity. Nevertheless, conditioned water with L. carinatus snails for 6 weeks decreased the egg laying capacity of B. alexandrina snails, although the capacity was significantly increased when the conditioning was combined with Lannate residue as well. Hatchability was significantly declined when the eggs were laid in treated-conditioned water and left to hatch either in the same kind of water or in dechlorinated tap water