Target Product Profiles (TPP) for the development of new diagnostic tools for the detection of new and azithromycin-resistant cases of yaws
Overview
Yaws has been targeted for eradication since the mid-20th century. Previous efforts focused on the use of mass or targeted treatment with penicillin. Although these efforts reduced the prevalence of yaws by > 90%, they were ultimately not successful at achieving eradication. In 2012, WHO launched a new strategy – the Morges strategy – based on mass treatment with azithromycin. Central to this strategy is the identification of all endemic communities, followed by community mass treatment. Small-scale pilot projects of this strategy have been implemented in several settings.
Once the number of yaws cases has fallen, ongoing case-finding and treatment is required to identify and treat remaining cases and their close contacts. Once no further cases of yaws are detected, the programme switches to surveillance, including serological surveillance of children aged < 5 years.
As the aim of the programme is eradication, detection of single cases is important. This detection occurs in two scenarios: (i) deciding whether to initiate a programme – in this setting, finding a single yaws case is sufficient to declare a community endemic and needing treatment; and (ii) surveillance after mass treatment – in this setting, it is important to exclude that even a single suspected case is truly yaws and therefore that interventions can stop.
A major concern has been the identification of a small number of cases of yaws in whom resistance to azithromycin has developed. Two mutations are known to confer resistance to azithromycin. Detection of phenotypic resistance is complicated by the inability to routinely culture T. pallidum, and therefore the focus of resistance detection is to identify (a) cases of clinical treatment failure, and (b) known mutations associated with resistance to azithromycin.
The new road map for neglected tropical diseases 2021–2030 has set a target of yaws eradication by 2030.
