Abstract
Extracts of 49 plant species were screened for ability to kill mollusks, cercaria, or miracidia. At concentrations of 100 ppm in ethanol, 23 extracts killed all Biomphalaria alexandrina snails, the host for the cercaria and miracidia of Schistosoma mansoni, the parasite that causes schistosomiasis. Total mortality of the cercaria and miracidia was found for 11 and eight extracts, respectively, at concentrations of 500 ppm in ethanol. Dry powders of the active extracts were generally highly toxic to the organisms. Of the eleven species that were effective as powders or extracts, Acacia nilotica was toxic to the snail and Thymus capitatus and Syzygium aromaticum were toxic to all three organisms.