Assessment of Molluscicidal, Cercericidal and Miracicidal Activities of Crude Extracts of Azadirachta indica and Entada leptostachya

Abstract

Schistosomiasis infections in humans depend absolutely on the presence of intermediate host. Control of the intermediate host disrupts the cycle of schistosomes stopping transmission of schistosomiasis. Synthetic molluscicides used today are expensive and toxic to non-target organisms. Herbal preparations which do not affect non-target organisms would be a key in controlling schistosomiasis. This study was done to determine if plant extracts of Entada leptostachya and Azadirachta indica exhibit molluscicidal, cercericidal and miracicidal activities. Biomphalaria pfeifferi adult snails and juveniles, Schistosoma mansoni cerceriae and miracidia were used in the study. Groups of uninfected snails were exposed to different concentrations of water, methanol and ethyl acetate crude extracts obtained from the two plants. Controls were also set; positive control (Niclosamide) and negative control (Distilled water). Miracidia and cerceriae were exposed to the most active plant extract on juvenile and adult snails. Data analysis was done using Finney probit analysis to estimate the LD₅₀ values of the crude extracts on snails and LT₅₀values of the crude extracts on cerceriae and miracidia. Only methanol extract of E. leptostachya was found to exhibit the highest molluscicidal activity on juveniles and adults with a LD₅₀ value of 30.21 mg/l and 40.93 mg/l respectively (P ? 0.05). Methanol extract of A. indica, aqueous and ethyl acetate extracts of A. indica and E. leptostachya were nontoxic to both adult and juvenile snails. On the other hand, methanol extract of E. leptostachya were found to have cercericidal and miracicidal activity. The LT₅₀ of miracidia and cerceriae was 7.69 minutes and 4.25 minutes respectively at a concentration 80 mg/l (P ? 0.05). Phytochemical screening of the methanol, aqueous extracts and ethyl acetate extracts of A. indica and E. leptostachya confirmed the presence of flavonoids, saponins, tannins, alkaloids, triterpenes and sterols. Results suggest that methanolic root extract of E. leptostachya has molluscicidal activity against Biomphalaria pfeifferi. The results also indicate that methanolic root extract of E. leptostachya have cercaricidal and miracicidal activity against the schistosome larval stages.

Keywords: Azadirachta indica,  Entada leptostachya, Biomphalaria pfeifferi, Crude extracts, Phytochemical screening, Molluscicidal activity, Cercericidal activity and Miracicidal activity