Molluscicidal activity of selected plant extracts

Abstract

Schistosomiasis is one of the most widespread paras itic infections and the third most prevalent parasitic disease in the world in terms of overall morbidity, socioeconomic and public health importan ce. It is the most prevalent of water borne and parasitic diseases and it affects over 240 million people worldwide. One approach to the contr ol of the disease is the elimination of the intermediate host responsibl e for its transmission. The use of synthetic molluscicides is becoming unpo pular owing to their high cost and enviromental pollution. As a result, plant molluscicides have received considerable attention in the search for c heaper alternatives to chemotherapy and synthetic molluscicides in schisto somiasis control. The aim of this study was to determine the molluscicida l activity of aqueous and ethanol extracts from five plant species; Ocimum americanum, Sonchus luxurians, Aloe secundiflora, Bridelia micr antha and Croton megalocarpus against Biomphalaria pfeifferi adult and juvenile snails. Dried plant materials were ground into powder. They were extracted using ethanol and water. Phytochemicals were detected whi ch include; flavonoids, saponins, tannins, alkaloids, glycoside s, steroids and triterpenes. Adult and juvenile snails were subjected to concent rations of 5 mg/l, 10 mg/l, 20 mg/l and 40 mg/l of the aqueous and eth anol plant extracts. Generally, only B. micrantha which had molluscicidal effect against adult and juvenile snails. B. micrantha, extracts that were found to have mollus- cicidal effects, were screened for their miracicida l and cercaricidal activity xiv against Schistosoma mansoni miracidia and cercariae. Concentrations of 5 mg/l, 10 mg/l, 20 mg/l and 40 mg/l were used. The ability of B.micrantha aqueous extract to immobilise miracidia and cercari ae was greater than that of the ethanol extract. From this study, B.micrantha demonstrated molluscicidal, miracicidal and cercari cidal effects.