Molluscicidal effect of fenitrothion and anilofos on Lymnaea natalensis and Biomphalaria alexandrina snails and on the free larval stages of Schistosoma mansoni

ABSTRACT

Pesticides; fenitrothion and anilofos [aniloguard] were tested as molluscicides against Lymnaea natalensis and Biomphalaria alexandrina. The LC 50 and LC 90 of fenitrothion was 0.12 and 0.21 ppm for L. natalensis and 0.l7 and.26 ppm for B. alexandrina, respectively. The LC 50 and LC 90 anilofos was 2.61 and 6.47 ppm for Lymnaea and 3.07 and 8.6 ppm for Biomphalaria. The effect of sublethal concentrations [LC 0, LC 5 and C 10] of Feni-rothion on B. alexandrina growth rate, eggs hatchability and on free larval stages of Schistosoma mansoni [miracidia and cercariae] were studied. The results obtained showed that sublethal concentrations of fenitrothion caused reduction in growth rate of B. alexandrina and reduction in the hatchibility of snails eggs. The mortality rates of miracidia and cercariae were elevated by increasing both the concentrations of fenitrothion and the time of exposure. The results showed that fenitrothion was more toxic to the free larval stages of S. mansoni than to their snails. The results showed a significant reduction in total protein of treated snails when compared with controls in haemolymph while there was an increase of protein contents of the tissue. The AlkP enzyme activity was slightly increased in the haemolymph of experimental groups than the control and in the tissues the values were significantly higher when compared with control. ALT enzyme activity in haemolymph of experimental groups was higher than controls while its activity in tissue was lower. AST enzyme activity was higher in haemolymph and tissue of experimental groups than in controls