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Aggregation in schistosomiasis: comparison of the relationships between prevalence and intensity in different endemic areas

Published online by Cambridge University Press:  06 April 2009

H. L. Guyatt ,
T. Smith ,
B. Gryseels ,
C. Lengeler ,
H. Mshinda ,
S. Siziya ,
B. Salanave ,
N. Mohome ,
J. Makwala  and
K. P. Ngimbi
...Show all authors
H. L. Guyatt
Affiliation:
Department of Public Health and Epidemiology, Swiss Tropical Institute, Socinstrasse 57, Basel CH-4002, Switzerland
T. Smith
Affiliation:
Department of Public Health and Epidemiology, Swiss Tropical Institute, Socinstrasse 57, Basel CH-4002, Switzerland
B. Gryseels
Affiliation:
Department of Parasitology, University of Leiden, P.B. 9605, 2300 RC Leiden, The Netherlands
C. Lengeler
Affiliation:
Tropical Health and Epidemiology Unit, London School of Hygiene and Tropical Medicine, Keppel Street, London WCIE 7HT, UK
H. Mshinda
Affiliation:
Ifakara Centre, PO Box 53, Ifakara, Tanzania
S. Siziya
Affiliation:
Tropical Diseases Research Center, POB 71 769 Ndola, Zambia
B. Salanave
Affiliation:
IFORD, B.P. 1556, Yaoundé, Cameroon
N. Mohome
Affiliation:
OCEAC, B.P. 288, Yaoundé, Cameroon
J. Makwala
Affiliation:
Département de Démographie, Université de Kinshasa, Zaire
K. P. Ngimbi
Affiliation:
Département de Démographie, Université de Kinshasa, Zaire
M. Tanner
Affiliation:
Department of Public Health and Epidemiology, Swiss Tropical Institute, Socinstrasse 57, Basel CH-4002, Switzerland
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Summary

Distributions of the intensities of helminth infections within their host populations are invariably aggregated. In the case of the intestinal nematodes, the degrees of aggregation have been shown to be species specific, and constant for any given species despite geographical variation in study sites. This species-specific aggregation can be quantified and used as a tool in planning control interventions. One practical application is that the prevalence of infection can be used to predict the prevalence of heavy infection and thus the risks of morbidity. This paper investigates the patterns of aggregation in schistosome egg counts in different endemic areas in Africa (data sets were obtained from Burundi, Cameroon, Tanzania, Zambia and Zaire). The analysis demonstrates that the degree of parasite aggregation, for both Schistosoma mansoni and S. haematobium, differs amongst the different study localities. This is probably due to area-specific differences in host exposure and immunity. This implies that for these schistosome species, it is not possible to predict egg count distributions or morbidity levels from prevalence data alone.

Keywords

Schistosoma mansoniSchistosoma haematobiumprevalenceintensityepidemiologycontrol
Type
Research Article
Information
Parasitology , Volume 109 , Issue 1 , July 1994 , pp. 45 - 55
Copyright
Copyright © Cambridge University Press 1994

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