Millettia thonningii molluscicide: A rapid knockdown cercaricide for schistosome cercariae

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Abstract
Suspensions of ground seed material from the West African legume, Millettia thonningii, have previously been shown to be molluscicidal to schistosome‐transmitting snails and thus potentially useful as a control agent for schistosomiasis. It is demonstrated here that Millettia seed suspensions, in addition to their molluscicidal action, show considerable toxicity towards the infective cercarial stage of Schistosoma mansoni, a causative agent of human intestinal schistosomiasis. This toxicity consists of a rapid knockdown effect on the cercariae, producing unresponsive immobility in times from 11 to 42 min in a concentration range from 500 to 100 parts per million. Filtering reduced the speed of this effect. Cercaricidal activity of the suspensions is also demonstrated in a range of unfiltered suspension concentrations, with 100% mortality occurring from 120 to 310 min after exposure. This potent action will add to the potential effectiveness of a Millettia molluscicide preparation when used as a control agent for schistosomiasis.