The Lancet has published a new study led by Oriol Mitjà, first author and researcher at the Barcelona Institute for Global Health (ISGlobal), a centre supported by the “la Caixa” Foundation, which concludes that yaws eradication will require more than a single round of mass drug treatment indicated in the current WHO strategy.

Based on these results, Mitjà will launch in April 2018 a new project in Papua New Guinea with the goal of determining how many mass treatments are required, thereby guiding the WHO on the optimal strategy for yaws elimination.

ISGlobal researcher Oriol Mitjà meets with a community in Papua New Guinea affected by yaws, a tropical skin disease Image/David Fontseca
ISGlobal researcher Oriol Mitjà meets with a community in Papua New Guinea affected by yaws, a tropical skin disease
Image/David Fontseca

Azithromycin resistance is reported for the first time

In 2012, Mitjà’s team established that one single dose of azithromycin was enough to cure yaws. This discovery became the cornerstone of the current WHO strategy of mass drug administration to achieve disease elimination by 2020. However, study published in The Lancet concludes that yaws eradication will require the administration of at least two antibiotic doses per person, spaced by 6-12 month intervals.

The international research team presents results obtained 42 months after a mass drug administration treatment in Lihir Island, Papua New Guinea, where 84% of the population received one single dose of azithromycin. A clinical, serological and molecular follow-up was performed to detect active yaws cases (i.e. ulcers where the presence of the causal agent, Treponema pallidum pertenue, was confirmed by DNA amplification). The results show a steep decline in disease prevalence after 18 months of treatment, but a re-emergence after 24 months and an increase to 0.4% after 42 months. Most cases were individuals that were absent at the time of treatment, although there were also imported cases from other regions.

Non-venereal treponematoses: yaws

“Our study underlines the need to treat every individual living in an endemic zone, in order to cure latent infections. Therefore, yaws could be eliminated with repeated rounds of mass treatments” explains the ISGlobal researcher and physician at the Hospital Clinic of Barcelona.

For the first time, the authors identified five T. p. pertenue infections that were resistant to azithromycin as a result of a mutation identified by laboratory techniques in Seattle, USA. The five children lived in the same village and were relatives or friends, indicating that they were infected by the same resistant strain. They were cured only after a penicillin benzathine injection.

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“This study reveals the urgent need to include drug resistance monitoring as part of the WHO yaws eradication strategy” explains ISGlobal General Director Antoni Plasència.

Finding the optimal strategy for yaws elimination

The new 24-month project that Mitjà’s team will launch next April in the province of New Ireland, Papua New Guinea aims to identify how many rounds of mass treatment are necessary to achieve yaws elimination and will reach a total of 50,000 people. The results will help the WHO elaborate action guidelines for the governments of affected countries.