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A comparative evaluation of snail sampling and cercariometry to detect Schistosoma mansoni transmission in a large-scale, longitudinal field-study in Machakos, Kenya

Published online by Cambridge University Press:  06 April 2009

J. H. Ouma ,
R. F. Sturrock ,
R. K. Klumpp  and
H. C. Kariuki
J. H. Ouma
Affiliation:
Division of Vector-borne Diseases, Ministry of Health, P.O. Box 20705, Nairobi, Kenya
R. F. Sturrock
Affiliation:
Department of Medical Parasitology, London School of Hygiene and Tropical Medicine, Keppel Street (Gower Street), London WC1E 7HT, England
R. K. Klumpp
Affiliation:
147 Laurel Street, Atherton, California 94025, USA
H. C. Kariuki
Affiliation:
Division of Vector-borne Diseases, Ministry of Health, P.O. Box 20705, Nairobi, Kenya
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Summary

In an operational Schistosoma mansoni field-study in an area of about 20 km (population approximately 8000), transmission detection by simple snail sampling was compared with cercariometry. Between 1985 and 1987, 62 field sites were sampled at fortnightly intervals. Of a total of 2758 field observations, 89.8% gave full snail data; 64.4% full cercarial data; and 61.7% complete data for both methods. The complete data sets showed significant but not strong correlations between Biomphalaria pfeifferi (total and infected with S. mansoni or other trematodes) and cercarial (S. mansoni and non-human) recoveries. Non-human (but not S. mansoni) cercarial recovery decreased with deteriorating cercariometry filter quality. Both snail and cercarial recoveries diminished significantly with increasing water flows at the time of collection. Many samples yielded infected snails or cercariae, but not both, and neither method detected significantly more transmission sites. The method of choice for detecting transmission in a large-scale field-study depends on logistical and financial considerations. Relatively simple snail sampling allows quick, cheap and widespread data collection adequate for most purposes but more complicated cercariometry is still valuable for specific, small-scale studies.

Keywords

Schistosoma mansonicercariasnailtransmission.
Type
Research Article
Information
Parasitology , Volume 99 , Issue 3 , December 1989 , pp. 349 - 355
Copyright
Copyright © Cambridge University Press 1989

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