Control strategies for sleeping sickness in Central Africa: a model‐based approach

Abstract

Vector control and the detection (followed by treatment) of infected individuals are the two methods currently available for the control of sleeping sickness. The basic reproduction rate of a compartmental model is used to analyse and compare the two strategies. The efficiency of each strategy will depend on two epidemiologic parameters; the intrinsic contamination rate Q (closely related to the index of new contaminations) that captures the potential spread of the disease, and the intrinsic removal rate from the first stage (intrinsic to the particular trypanosome strain and to the population's susceptibility). The model shows that when the intrinsic removal rate is low (that is, when there is a long first stage characteristic of an endemic situation) the detection of sick individuals is more efficient than vector control. The situation is reversed when the removal rate is high (in an epidemic situation). The conclusions of the analysis are shown to be in general agreement with results obtained in two different sleeping sickness foci of Central Africa.

The Natural Progression of Gambiense Sleeping Sickness: What Is the Evidence?

“…If the existence of a trypano-tolerant infection reservoir were demonstrated, case detection strategies could be adapted, for example by introducing systematic serological treatment (see above) and ensuring very high screening coverage (based on modelling work previously published by others [71],[72] and currently being done in our group, it is likely that elimination would not require detecting all chronic carriers). New safe and easily administered (i.e., oral) drugs would also help to maximise treatment coverage.…”

Analysis of a model of gambiense sleeping sickness in humans and cattle

“…The Bendixson-Dulac criterion on the system (1)- (2) shows that there can be no periodic solution in D. Thus the Poincaré-Bendixson theorem; see, for example [ [26, p. 9], [9, Theorem 1, p. 327, 329]], shows that the unique positive equilibrium (L * , A * ) is globally asymptotically stable in int(D).…”

“…They included susceptible, incubating, asymptomatic and removed humans, and compared their model results with data from the Democratic Republic of Congo. In a subsequent paper, these authors [2] used their model to compare control strategies. Chalvet-Monfray et al [7] then extended this to two patches, to model a village and plantations.…”

Is vector control needed to eliminate gambiense human African trypanosomiasis?

“…However, there are several foci where active case detection and treatment without vector control, despite saving many lives, has failed to bring HAT under effective control. Artzrouni and Gouteux (1996) developed a mathematical model of the basic Reproductive Number ( R 0 ) to analyse and compare vector control and active case detection and treatment in the control of gambiense HAT (see also Gouteux and Artzrouni, 1996). They showed that when transmission rates are high (strongly influenced by fly biting rates on humans) vector control is a requirement.…”

“…This means that reduction in tsetse densities, even those not reaching total elimination, will also reduce transmission. Re-analysis of the theoretical models developed by Artzrouni and Gouteux (1996) suggest that transmission can be halted without the elimination of tsetse (Hastings, unpublished data).…”