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Epidemiology of trypanosome infections of the tsetse fly Glossina pallidipes in the Zambezi Valley

Published online by Cambridge University Press:  06 April 2009

M. E. J. Woolhouse ,
J. W. Hargrove  and
J. J. McNamara
M. E. J. Woolhouse
Affiliation:
Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS
J. W. Hargrove
Affiliation:
ODA Insect Pest Management Initiative, c/o Tsetse and Trypanosomiasis Control Branch, Box 8283, Causeway, Zimbabwe
J. J. McNamara
Affiliation:
Tsetse Research Laboratory, Department of Veterinary Medicine, University of Bristol, Langford, Bristol BS18 7DU
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Summary

The epidemiology of trypanosome infections of Glossina pallidipes was studied at a riverine site in the Zambezi Valley, Zimbabwe for a period of 13 months. Over 9000 flies were captured using a single trap. These flies were dissected, screened for trypanosome infection, sexed, and aged using both wing fray and (for females) ovarian category indices. Midgut infections were identified to species using recently developed DNA probes. The overall prevalence of mature infections was 5·5%, comprising 3·1% Trypanosoma vivax-type and 2·4% T. congolense-type (which included very low prevalences of T. brucei, T. simiae and another Nannomonas species). The prevalence of infection increased with age. For T. vivax-type infections in flies aged by ovarian category this relationship could be described by a simple ‘catalytic’ model assuming a constant per capita rate of infection. For T. congolense-type infections this model tended to over-estimate prevalence in older age classes, implying that the rate of infection decreases with age, and/or that infected flies have higher mortality rates, and/or that a significant fraction of the population is resistant to infection. Prevalences of infection also varied between months. This variation was more marked for T. vivax-type infections and was negatively correlated with both temperature and rainfall. The shape of the age-prevalence relationship, however, did not vary significantly between months. These observations are not fully explained by variation in the age-structure of the tsetse population and are consistent with temporal variation in the rate of infection (rather than in the trypanosome developmental period or in effects of infection on fly mortality). Possible causes of this variation are discussed.

Keywords

age–prevalenceDNA probeseasonalityTrypanosoma spp.tsetse flyZimbabwe
Type
Research Article
Information
Parasitology , Volume 106 , Issue 5 , June 1993 , pp. 479 - 485
Copyright
Copyright © Cambridge University Press 1993

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