Difference in the susceptibility to certain molluscicides and Schistosoma mansoni infection of three forms Egyptian Biomphalaria glabrata.

The first generation of 3 morphologically different forms of B. glabrata collected from Giza were compared for LC50 values susceptibility to bayluscide and copper sulphate (chemical molluscicides) and Anagallis arvensis and Calendula micrantha (plant molluscicides) and to Schistosoma mansoni infection. Form (2) as juvenile and adult were less sensitive to C. micrantha and A. arvensis. Form (3) as juvenile and form (1) as adult were least sensitive to CuSO4. Approximately the same susceptibility to bayluscide was observed in the 3 forms either as juvenile or adult. The sublethal concentrations of the molluscicides on B. glabrata 3 forms showed no significant difference in the growth or survival rate in between. Form (2) was significantly higher in the egg lying capacity. The total protein concentration was not affected except in certain cases where the increase was primarily due to the increase in the globulin concentrations which indicate with the marked increase observed in the urea concentration and marked increase or inhibition in the activity of either AST or ALT that the digestive gland of the 3 forms of snails is seriously affected by molluscicides. The 3 forms of B. glabrata showed low susceptibility to infection with the local strain of S. mansoni.

In vivo, attenuation of schistosome cercarial development and disturbance of egg laying capacity in Biomphalaria alexandrina using sublethal concentrations of plant molluscicides.

The dry powdered of Sinapis arvensis, Thymelaea hirsuta, Callistemon lanceolatus and Peganum harmala showed molluscicidal activity against Biomphalaria alexandrina, specific intermediate hosts to Schistosoma mansoni. Effect of LC25 of dry powdered plant molluscicides 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 LC50 compared to S. arvensis, T. hirsuta, and P. harmala. LC25 of the latter three plants resulted in more significant inhibition of HK, GPI, AMP-deaminase and PO than C. lanceolatus. Treatment of snails with LC10 of these plants markedly affected compatibility of B. alexandrina to S. mansoni infection. Significant decrease in cercarial production 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.