Discussion
On behalf of the Tiny Targets Programme
Sleeping sickness (human African trypanosomiasis, HAT) is a neglected tropical disease which is fatal if untreated. The most common (>90% of cases) form of the disease occurs in west and central Africa and is caused by
T. b. gambiense (gHAT) transmitted by riverine species of tsetse. A programme of mass screening and treatment of cases, co-ordinated by the WHO, reduced the number of cases reported globally from an average of ~23,000 (range=10,987-37,385) cases in the 1990s to ~7,000 cases/year by 2010. Control of the tsetse vectors did not play a major role during this period due to the costs and logistical constraints associated with the available technologies. To address this, an international collaboration of researchers and industry undertook field research on the host-finding behaviour of riverine tsetse. This led to the development of Tiny Targets, insecticide-treated baits which attract and kill riverine tsetse. Initial field trials in Uganda, Chad and Guinea demonstrated that Tiny Targets could reduce tsetse densities by >80% at a reduced cost (<20%) compared to standard methods of tsetse control. Following these successful trials, Tiny Targets were introduced in Côte d’Ivoire and Democratic Republic of Congo (DRC) and implemented alongside screening and treatment. These five countries historically accounted for >80% of gHAT cases. Modelling has demonstrated the impact of Tiny Targets on disease incidence. In Chad for instance, >70% of a decline in the annual incidence of gHAT in the Mandoul focus was due to the deployment of Tiny Targets. Tiny Targets have contributed to achieving the WHO 2020 goal of reducing the number of new cases to fewer than 2,000 per year, achieved consistently since 2017. In 2021, WHO declared that Côte d’Ivoire had achieved elimination of gHAT as a public health problem, and in 2022 Uganda also achieved this milestone; the role of Tiny Targets in this success was recognised in both countries. More recently, Tiny Targets have been introduced in South Sudan and Angola and continue to be scaled-up in DRC, the country with the largest burden of disease. Introduction of Tiny Targets to other countries where gHAT persists is required to meet WHO’s 2030 goal of eliminating transmission of gHAT.
