Skin infections with ulceration are a major health problem in the South Pacific countries. Yaws, diagnosed by the presence of cutaneous ulcers (CU) and a reactive syphilis serology, is one important cause, but this can be confused clinically with ulcers due to other aetiologies. In a prospective cohort study in yaws-endemic villages of a Papua New Guinean (PNG) island we showed that Haemophilus ducreyi is the leading cause of chronic CU in children; nearly 60% of patients with ulcers had detectable lesional H. ducreyi DNA, while 35% were Treponema pallidum subsp. pertenue positive. Similar findings were reported from yaws endemic communities in the Solomon Islands, Vanuatu and Ghana. Unlike yaws, H. ducreyi lesions appear to be restricted to the skin and, if left untreated, do not result in inflammatory lesions of the bones. Whole-genome sequencing studies have shown that CU strains of H. ducreyi are remarkably similar to class I genital ulcer (GU) strains with an overall sequence similarity of 99.98%, and that CU strains diverged from class I strains ≈0.18mya which supports the idea that CU with H. ducreyi preceded syndromic management of GU. A single oral dose of azithromcycin (AZ, 30 mg/Kg) is effective for treatment of yaws and, cutaneous strains of H. ducreyi have been shown to be susceptible to macrolides. In the context of new efforts to eradicate yaws, the use of mass treatment with azithromycin in PNG reduced the absolute prevalence of yaws CU from 2.4 to 0.3 percent at 12 months after treatment, and H. ducreyi CU from 2.7% to 0.6%. The persistence of skin ulcers in the population raises the possibility that the bacteria may exist in an environmental reservoir or are so infectious that MDA at less than 100% above coverage rate fails to eradicate the diseases from a community.
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