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A further model for temporal patterns in the epidemiology of schistosome infections of snails

Published online by Cambridge University Press:  06 April 2009

M. E. J. Woolhouse  and
S. K. Chandiwana
M. E. J. Woolhouse
Affiliation:
Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS
S. K. Chandiwana
Affiliation:
Blair Research Laboratory, P.O. Box 8105, Causeway, Harare, Zimbabwe
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Extract

The prevalence of Schistosoma mansoni infections of Biomphalaria pfeifferi shows seasonal variation. Field data from Zimbabwe show annual ranges from 0 to 7%. In this paper a mathematical model of B. pfeifferi population dynamics and S. mansoni epidemiology is used as a framework for analysis of these patterns. Snail fecundity is a function of snail age and of temperature, and is apparently affected by other seasonal factors. The pre-patent period is dependent on temperature. Infection affects snail fecundity and mortality. Parameter values are derived from previous field and laboratory studies. The force-of-infection is estimated from the analysis of size-prevalence data. Using observed temperatures, model output agrees well with field data on snail abundance and prevalence of infection over a 14-month period. Seasonal variation in prevalence largely reflects variation in the pre-patent period and in snail population age structure. The possible role of seasonality in the force-of-infection is discussed. Prevalence patterns are not greatly affected by year-to-year differences in temperature. Significant seasonal variation in snail–man transmission rates is expected.

Keywords

Biomphalaria pfeifferiepidemiologymathematical modelSchistosoma mansoniseasonality
Type
Research Article
Information
Parasitology , Volume 104 , Issue 3 , June 1992 , pp. 443 - 449
Copyright
Copyright © Cambridge University Press 1992

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