Molluscicidal and physiological activities of some plants against biomphalaria Alexandria snails

ABSTRACT

The molluscicidal activity of three plants Nerium oleander, Dizygotheca elegantissima and A gave decipiens on Biomphalaria Alexandrina snails at different exposure intervals and size or age of snails was studied throughout the present investigation. Also, the effects of these selected plants on Schistosoma mansoni cercariae and miracidia were assessed. Moreover, the role of sublethal concentrations of these plants on physiological processes and functions on the hemolymph of these snails was also clarified. Results showed that N. oleander proved the most effective plant as its LC[90] was 100ppm after 24hrs from exposure compared with the values of 120 and 180 ppm with the plants D. elegantissima and A. decipiens, respectively. The elongation of remarkable exposure periods from 24 to 48 hrs increased the molluscicidal activities of the tested plants. Different sizes or ages of Biomphalaria Alexandrina snails showed different susceptibility levels towards the action of the tested plants. Newly hatched snails were the most sensitive group. When the LC[50] and LC[90] of the experimental plants were tested against the cercariae, almost 100% of cercarial mortality was obtained after only two hrs when used 100, 120 and180 ppm for Nerium oleander, Dizygotheca elegantissima and Agave decipiens, respectively. Meanwhile, 100% miracidia mortality was obtained after 1 hr when exposed to the same concentrations. Thus miracidia proved more susceptible than cercariae. While used the sublethal concentrations of these plants, the LC[0] of the three tested plants showed moderate significant increase in transaminases activities. The total protein, albumin and globulin were slightly changed; while the A/G ratio did not record any changes between treated and control snails. The application of plant molluseicides resulted in marked increase of total lipid content; the maximal observation was recorded with the use of both N. oleander, and D. elegantissima