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Attenuation of Schistosoma mansoni cercariae with a molluscicide derived from Millettia thonningii

Published online by Cambridge University Press:  06 April 2009

S. Perrett
Affiliation:
Infection and Immunity Research Group, Division of Life Sciences, King's College London, London W8 7AH
P. J. Whitfield
Affiliation:
Infection and Immunity Research Group, Division of Life Sciences, King's College London, London W8 7AH
A. Bartlett
Affiliation:
North East Surrey College of Technology, Reigate Road, Ewell, Surrey KT13 3DS
L. Sanderson
Affiliation:
Infection and Immunity Research Group, Division of Life Sciences, King's College London, London W8 7AH

Extract

A chloroform extract of molluscicidal plant secondary compounds from the seeds of a West African legume Millettia thonningii was used to attenuate cercariae of Schistosoma mansoni prior to infection of NMRI female mice. Exposure of cercariae to 0·3, 0·6, 1·3, 2·5, 10 or 20 mg/l concentrations of extract for 30 mm, immediately before standardized infection, was associated with a concentration-dependent decline in worm establishment at 55 days post-infection. The mean numbers of adult worms established declined from about 17 worms/mouse with control cercariae and those exposed to 0·3 mg/l Millettia to 0·1 worms/mouse after 10 mg/l pre-treatment. Mice exposed to cercariae after 20 mg/l pre-treatment had no adult worms at 55 days post-infection. The activities of cercariae 30 mm after exposure to Millettia extract at concentrations up to 2·5 mg/l were similar to those of control larvae: none was immobile. Exposure to higher concentrations of Millettia progressively reduced swimming activity and increased the proportion of immobile cercariae. After pretreatment with 20 mg/l Millettia the majority of larvae were immobile. Levels of anti-parasite antibodies (estimated by ELISA assay using an adult worm-based antigen preparation) rose between 21 and 55 days p.i. with control cercariae and those pre-treated with 2·5 mg/l Millettia. After 5 mg/l pre-treatment, cercariae induced a reduced antibody rise, while mice exposed to cercariae after 10 mg/l pre-treatment showed no rise in anti-parasite antibody levels. These results are discussed in the context of protocols which could possibly use Millettia-attenuated cercariae to induce useful levels of protection in mice towards further cercarial challenge.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1994

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