Reducing Human-Tsetse Contact Significantly Enhances the Efficacy of Sleeping Sickness Active Screening Campaigns: A Promising Result in the Context of Elimination

Abstract

BackgroundControl of gambiense sleeping sickness, a neglected tropical disease targeted for elimination by 2020, relies mainly on mass screening of populations at risk and treatment of cases. This strategy is however challenged by the existence of undetected reservoirs of parasites that contribute to the maintenance of transmission. In this study, performed in the Boffa disease focus of Guinea, we evaluated the value of adding vector control to medical surveys and measured its impact on disease burden.MethodsThe focus was divided into two parts (screen and treat in the western part; screen and treat plus vector control in the eastern part) separated by the Rio Pongo river. Population census and baseline entomological data were collected from the entire focus at the beginning of the study and insecticide impregnated targets were deployed on the eastern bank only. Medical surveys were performed in both areas in 2012 and 2013.FindingsIn the vector control area, there was an 80% decrease in tsetse density, resulting in a significant decrease of human tsetse contacts, and a decrease of disease prevalence (from 0.3% to 0.1%; p=0.01), and an almost nil incidence of new infections (<0.1%). In contrast, incidence was 10 times higher in the area without vector control (>1%, p<0.0001) with a disease prevalence increasing slightly (from 0.5 to 0.7%, p=0.34).InterpretationCombining medical and vector control was decisive in reducing T. b. gambiense transmission and in speeding up progress towards elimination. Similar strategies could be applied in other foci.

Adding tsetse control to medical activities contributes to decreasing transmission of sleeping sickness in the Mandoul focus (Chad)

“…This echoes the recent findings from Guinea where tsetse control also resulted in a significant decrease of the incidence of HAT [3]. …”

Predicting the Impact of Intervention Strategies for Sleeping Sickness in Two High-Endemicity Health Zones of the Democratic Republic of Congo

“…In recent years, great improvements to curative drugs and screening programmes have contributed to a substantial decline in disease incidence [1]. In addition, advances in tsetse control have meant that control programmes can use strategies with interventions against both the parasite and vector [2, 3]. …”

“…In areas which have already implemented vector control via tiny targets, a sharp decrease in tsetse abundance has been observed; there has been a reported 80% reduction to tsetse populations in Guinea [3] and 90% reduction in Uganda [2]. To complement regular medical surveillance, such tsetse control has the potential to help push towards elimination of this disease.…”

“…Tsetse are attracted to the target, contact it and, in so doing, pick up a lethal dose of insecticide. Trials in Guinea [3], Kenya and Uganda [2] have shown that deployment of tiny targets can reduce densities of tsetse by 70% to >90%. The targets are cheap (∼US$ 1/target) and easy to deploy, hence control of the tsetse population can be achieved at US$ 84/km 2 [19].…”

A targeted door-to-door strategy for sleeping sickness detection in low-prevalence settings in Côte d’Ivoire

“…In this context, targeted vector control measures, such as the deployment of insecticide-impregnated targets where FHAT or NHAT individuals are exposed to tsetse flies, could significantly reduce the risk of secondary infections and help interrupt transmission. Reducing human-tsetse contacts with impregnated targets was recently shown to be efficient in reducing new infections in the active HAT focus of Boffa in Guinea [4]. …”