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Observations on the effects of different chemotherapy strategies on the transmission of Schistosoma mansoni in Machakos District, Kenya, measured by long-term snail sampling and cercariometry

Published online by Cambridge University Press:  06 April 2009

R. F. Sturrock ,
R. K. Klumpp ,
J. H. Ouma ,
A. E. Butterworth ,
A. J. C. Fulford ,
H. C. Kariuki ,
F. W. Thiongo  and
D. Koech
R. F. Sturrock
Affiliation:
Department of Medical Parasitology, London School of Hygiene and Tropical Medicine, Keppel Street (Gower Street), London WCIE 7HT, UK
R. K. Klumpp
Affiliation:
147 Laurel Street, Atherton, California 94027, USA
J. H. Ouma
Affiliation:
Division of Vector-Borne Diseases, Ministry of Health, Nairobi, Kenya
A. E. Butterworth
Affiliation:
Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
A. J. C. Fulford
Affiliation:
Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
H. C. Kariuki
Affiliation:
Division of Vector-Borne Diseases, Ministry of Health, Nairobi, Kenya
F. W. Thiongo
Affiliation:
Division of Vector-Borne Diseases, Ministry of Health, Nairobi, Kenya
D. Koech
Affiliation:
Kenyan Medical Research Institute, Nairobi, Kenya
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Summary

Transmission of Schistosoma mansoni was monitored by routine snail sampling for Biomphalaria pfeifferi and by supplementary cercariometric measurements in 4 neighbouring study areas in Machakos District, Kenya. After 1 year, extensive, population-based chemotherapy with a single dose of praziquantel was given in 3 areas, but only minimal treatment in the fourth. In the year preceding treatment, seasonal transmission of S. mansoni and other non-human trematodes occurred in all 4 areas, despite some ecological differences and the effects of earlier treatment campaigns in 1 of the study areas. After treatment of all infected subjects in one area in which there had been earlier chemotherapy campaigns, S. mansoni transmission remained very low. It was reduced for at least 2 years after chemotherapy targeted at either all heavily infected subjects or all infected school children, but it was unaffected in an area where treatment was restricted to those few very heavily infected cases at risk of developing, disease. Nowhere was transmission entirely eliminated by chemotherapy and that of non-human trematodes continued unabated. The snail data correspond well with the human, parasitological data. Targeting school children was as effective as more extensive campaigns, but chemotherapy alone never stopped S. mansoni transmission: reinfection was inevitable, at rates determined by ecological factors affecting snail populations.

Keywords

Schistosoma mansoniBiomphalaria pfeifferisnailscercariatransmissionmass chemotherapy strategies
Type
Research Article
Information
Parasitology , Volume 109 , Issue 4 , November 1994 , pp. 443 - 453
Copyright
Copyright © Cambridge University Press 1994

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