ABSTRACT
The dry powder of Sinapis arvensis, Thymelaea hirsuta, Callistemon lanceolatus and Peganum harmala showed molluscicidal activity against Biomphalaria alexandrina, specific intermediate hosts to Schistosoma mansoni. Effect of LC[25] of dry powdered plant molluscicdes on hexokinase [HK], glucose phosphate isomerase [GPI], AMP deaminase, adenosine deaminase and phenol oxidase [PO] of B. alexandrina was traced. C. lanceolatus showed the highest molluscicidal activity as it has the lowest LC[50] compared to S. arvensis, T. hirsuta, and P. harmala, LC[25] of the latter three plants resulted in more significant inhibition of HK, GPI, AMP deaminase and PO than C. lanceolatus. Treatment of snails with LC[10] of these plants markedly affected compatibility of B. alexandrina to S. mansoni infection. Significant decrease in cercarial production was recorded in snails treated with sublethal concentrations of S. arvensis, T. hirsuta, and P. harmala. Remarkable impairment of the egg laying capacity of molluscicide treated snails was also recorded. Correlation between activity levels of HK, GPI and AMP deaminase and compatibility to parasitic infection and role of PO in the egglaying capacity of these snail species were discussed