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The possible role of Rickettsia-like organisms in trypanosomiasis epidemiology

Published online by Cambridge University Press:  06 April 2009

R. D. Baker
Affiliation:
Centre for Operational Research and Applied Statistics, University of Salford, Salford M5 4WT
I. Maudlin
Affiliation:
Tsetse Research Laboratory, University of Bristol, Langford, Bristol BSI8 7DU
P. J. M. Milligan
Affiliation:
Department of Biological Sciences, University of Salford, Salford M5 4WT
D. H. Molyneux
Affiliation:
Department of Biological Sciences, University of Salford, Salford M5 4WT
S. C. Welburn
Affiliation:
Tsetse Research Laboratory, University of Bristol, Langford, Bristol BSI8 7DU

Summary

A simple model of human and animal trypanosomiasis is proposed in which the Ross equation for disease transmission is supplemented by a differential equation describing the inheritance of susceptibility in the vector. The model predicts an equilibrium state of balanced polymorphism for the fraction, θ, of susceptible tsetse and the occurrence of periodic epidemics at roughly the observed intervals. A loss of infectivity to tsetse of mechanically transmitted strains of trypano some would seem to be a good evolutionary strategy for the trypanosome. The main implication for disease control is that measures initially reducing trypanosomiasis incidence could trigger off subsequent epidemics. Since θ leads incidence, monitoring θ could give several years advance warning of major epidemics.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1990

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