Research on tropical cutaneous ulcers and H. ducreyi

Traditionally, and due to lack of molecular confirmation tests in rural areas, all tropical Cutaneous Ulcers (CU) have been diagnosed as yaws, but recent research has shown that several pathogens can cause CU disease. Of particular importance has been the recent discovery of H. ducreyi as an agent of the condition.

After that discovery, our team has undergone numerous studies to understand more about this pathogen:

  1. Our study published in 2018 (Gonzalez-Beiras et al., 2016) concluded that up to 60% of CU clinically diagnosed as yaws are in fact caused by H. ducreyi, and that these ulcers are also affecting mostly children in remote communities of the South Pacific and West Africa.
  2. Treatment with azithromycin is the cornerstone of the yaws elimination campaign, and so we further provided definite clinical data on the efficacy of azithromycin to treat H. ducreyi CU (>95% healed) (Gonzalez-Beiras et al., 2017).
  3. Regardless of these results, MDA campaigns with azithromycin do not seem to have a long-term effect on the prevalence of H. ducreyi ulcers, and therefore we performed several studies on H. ducreyi dynamic of transmission, the impact of MDA on different strains (3) and its potential environmental reservoir (Houinei et al., 2017).

New strategies to control H. ducreyi along with yaws need to be explored. Syndromic care for ulcers using azithromycin and multiple rounds of MDA could be included in future interventions of the Morges Strategy for yaws eradication. Mathematical modelling has shown the value of multiple rounds of MDA to reduce T. p. pertenue infection, and this could, in parallel, reduce H. ducreyi infection and potentially skin carriage.