Background

Trypanosoma brucei (T b) gambiense is targeted to reach elimination as a public health problem by 2020 and full elimination by 2030. To achieve these goals, stakeholders need to consider strategies to accelerate elimination. Hence, we aimed to model several options related to current and emerging methods for case detection, treatment, and vector control across settings to assess cost-effectiveness and the probability of elimination.

Methods

Five intervention strategies were modelled over 30 years for low, moderate, and high transmission settings. Model parameters related to costs, efficacy, and transmission were based on available evidence and parameter estimation. Outcomes included disability-adjusted life-years (DALYs), costs, and long-term prevalence. Sensitivity analyses were done to calculate the uncertainty of the results.

Findings

To reach elimination targets for 2020 across all settings, approaches combining case detection, treatment, and vector control would be most effective. Elimination in high and moderate transmission areas was probable and cost-effective when strategies included vector control and novel methods, with incremental cost-effectiveness ratios (ICERs) ranging from US$400 to $1500 per DALY averted. In low transmission areas, approaches including the newest interventions alone or in combination with tiny targets (vector control) were cost-effective, with ICERs of $200 or $1800 per DALY averted, respectively, but only strategies including vector control were likely to lead to elimination. Results of sensitivity analyses showed that allowing for biennial surveillance, reducing vector control maintenance costs, or variations of active surveillance coverage could also be cost-effective options for elimination, depending on the setting.

Interpretation

Although various strategies might lead to elimination of T b gambiense , cost-effective approaches will include adoption of emerging technologies and, in some settings, increased surveillance or implementation of vector control.

Funding

Bill & Melinda Gates Foundation.

Human African trypanosomiasis, or sleeping sickness, is caused by Trypanosoma brucei (T b) gambiense and T b rhodesiense . Approximately 70 million people live in at-risk areas in sub-Saharan Africa. ¹ According to Global Burden of Disease (GBD) data from the Institute for Health Metrics and Evaluation (IHME), human African trypanosomiasis contributes an estimated 560 262 disability-adjusted life-years (DALYs) to the global burden of disease and ranks sixth in reference to the number of deaths among neglected tropical diseases. ² T b gambiense is primarily maintained in a human–tsetse cycle, whereas T b rhodesiense transmission entails a large spectrum of reservoir animals, mainly game. Thus, elimination efforts have primarily targeted T b gambiense .

In 2011, WHO published a roadmap towards overcoming the impact of ten neglected tropical diseases (NTDs), ³ and this commitment was renewed in January, 2012, as the London Declaration on Neglected Tropical Diseases, supported by the collaboration Uniting to Combat NTDs, became a new benchmark for elimination goals. It was then that the goal of control, described as reduction of disease to acceptable levels, was shifted to elimination, which pursues zero incidence in a defined geographical area. ⁴ Human African trypanosomiasis caused by T b gambiense was one of the diseases targeted for elimination as a public health problem by 2020, which is defined as less than one case per 10 000 people per year, ^{3 and 5} and complete elimination by 2030. As the year 2020 approaches, stakeholders committed to T b gambiense elimination have recognised that current interventions are resource-intensive, costly, and infeasible in remote or sociopolitically unstable areas, hindering foreseen elimination goals. ^{5 , 6 and 7} Moreover, with several emerging novel technologies and approaches for surveillance, diagnosis, treatment, and prevention (vector control) of T b gambiense , now is the time to investigate whether new technologies can accelerate elimination and, if so, how to allocate current resources to the right combination of interventions. ⁸

We aimed to analyse the cost-effectiveness of strategies for control and elimination of human African trypanosomiasis caused by T b gambiense and to forecast the effect of these approaches on disease transmission. The outcomes presented here aim to assist decision makers in determining which strategies are most likely to lead to elimination and will show good value for money.

Research in context

Evidence before this study

Efforts to estimate the financial resources needed for elimination of neglected tropical diseases have been done by WHO and collaborations including Uniting to Combat NTDs and The Lancet Commission on Investing in Health. Furthermore, in 2015 and 2016, several researchers used modelling exercises to investigate the probability of elimination with available interventions in west and central Africa. However, a full economic assessment of multiple interventions for human African trypanosomiasis caused by Trypanosoma brucei (T b) gambiense has not been attempted. Building on our previous work, in which we identified and considered new technologies as potential strategies to achieve elimination, we used a modelling approach to assess the cost-effectiveness and the probability of elimination of five intervention strategies.

Added value of this study

Our analysis shows that potential additional gains can be made with emerging technologies, particularly short or single-dose oral treatments (fexinidazole and the oxaborole compound SCYX-7158), rapid diagnostic tests, and tiny targets. We also addressed trade-offs between costs, health effects, and elimination timelines that need to be considered by decision makers. Additionally, our results indicate that strategic planning for elimination campaigns should be tailored to suit the transmission situation of a given focus.

Implications of all the available evidence

The results presented in this report harmonise the contributions of current and emerging technologies that will be available to eliminate sleeping sickness and show good value for money, hence providing national sleeping sickness control programmes and global funders with evidence-based solutions for the elimination of human African trypanosomiasis caused by T b gambiense .

Various scenarios of current interventions and emerging methods have been proposed for control and elimination of human African trypanosomiasis caused by T b gambiense . ⁹ We developed a series of strategies using these scenarios over time to ascertain which combination of interventions would be most likely to sustain control or accelerate towards elimination. After preliminary modelling ( appendix pp 29–38 ), we identified five strategies as relevant options for control or elimination of human African trypanosomiasis caused by T b gambiense , which are depicted in figure 1 and described in the appendix (p 1) .