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

Abstract

Two goals have been set for Gambian human African trypanosomiasis (HAT), the first is to achieve elimination as a public health problem in 90% of foci by 2020, and the second is to achieve zero transmission globally by 2030. It remains unclear if certain HAT hotspots could achieve elimination as a public health problem by 2020 and, of greater concern, it appears that current interventions to control HAT in these areas may not be sufficient to achieve zero transmission by 2030. A mathematical model of disease dynamics was used to assess the potential impact of changing the intervention strategy in two high-endemicity health zones of Kwilu province, Democratic Republic of Congo. Six key strategies and twelve variations were considered which covered a range of recruitment strategies for screening and vector control. It was found that effectiveness of HAT screening could be improved by increasing effort to recruit high-risk groups for screening. Furthermore, seven proposed strategies which included vector control were predicted to be sufficient to achieve an incidence of less than 1 reported case per 10,000 people by 2020 in the study region. All vector control strategies simulated reduced transmission enough to meet the 2030 goal, even if vector control was only moderately effective (60% tsetse population reduction). At this level of control the full elimination threshold was expected to be met within six years following the start of the change in strategy and over 6000 additional cases would be averted between 2017 and 2030 compared to current screening alone. It is recommended that a two-pronged strategy including both enhanced active screening and tsetse control is implemented in this region and in other persistent HAT foci to ensure the success of the control programme and meet the 2030 elimination goal for HAT.

The importance of vector control for the control and elimination of vector-borne diseases

“…While active screening and treatment have been responsible for the majority of this decline, in the last decade, new cost-effective methods of controlling riverine species of tsetse-the important vectors of T. b. gambiense-have begun to make an important contribution to the global effort. In particular, 'Tiny Targets' are-despite their small size-proving highly effective in reducing the density of riverine species where active screening and treatment alone is not predicted to achieve the elimination goals [178,179]. Tiny Targets are currently deployed by control programmes in Chad, Côte d'Ivoire, the Democratic Republic of Congo, Guinea, and Uganda.…”

Modelling for policy: The five principles of the Neglected Tropical Diseases Modelling Consortium

“…From the start of the NTD Modelling Consortium in 2015, there have been several other examples of impactful modelling, which could be divided over three major scales of operations: (1) developing WHO guidelines (e.g., for triple-drug therapy, with ivermectin, diethylcarbamazine, and albendazole, against lymphatic filariasis [16,17]); (2) informing funding decisions for new intervention tools (e.g., the development of a schistosomiasis vaccine [18]); and (3) guiding within-country targeting of control (e.g., local vector control for human African trypanosomiasis in the Democratic Republic of the Congo [19,20] and Chad [21]).…”

Impact of Tiny Targets onGlossina fuscipes quanzensis, the primary vector of Human African Trypanosomiasis in the Democratic Republic of the Congo

“…Behavioural studies have shown that this species is responsive to Tiny Targets [13]. Accordingly, we implemented a large-scale trial of Tiny Targets in Yasa Bonga Health Zone, one of the foci where the addition of vector control to screening activities is predicted to accelerate progress towards the elimination goal [4,6]. To assist in the design and monitoring of the tsetse control operation, we also conducted a large-scale entomological survey of G. f. quanzensis in Yasa Bonga and its neighbouring health zones of Masi Manimba and Mosango ( Figure 1) and used remotely-sensed data to produce a map of tsetse habitat suitability for this important vector, which guided the deployment of targets and allowed us to assess their impact.…”