Treatment
Treatment is normally by a single intramuscular injection of long-acting benzathine benzylpenicillin, or less commonly by a course of other antibiotics, such as azithromycin or tetracycline tablets. Penicillin has been the front-line treatment since at least the 1960s, but there is no solid evidence of the evolution of penicillin resistance in yaws.The historical strategy for the eradication of yaws (1952–1964) was:
Benzathine benzylpenicillin requires a cold chain and staff who can inject it, and there is a small risk of anaphylaxis. It was also not reliably available during the 2010s; there have been supply shortages.In the 2010s, a single oral dose of azithromycin was shown to be as effective as intramuscular penicillin. Unlike penicillin, there is strong evidence that yaws is evolving antibiotic resistance to azithromycin; there are two known mutations in the bacterium, each of which can cause resistance and make the treatment ineffective. This has threatened eradication efforts.Within 8–10 hours of penicillin treatment, bacteria can no longer be found in lesion biopsies. Primary and secondary lesions usually heal in 2–4 weeks; bone pain may improve within two days. If treated early enough, bone deformities may reverse and heal. Primary and secondary stage lesions may heal completely, but the destructive changes of tertiary yaws are largely irreversible.If lesions do not heal, or RPR test results do not improve, this may indicate treatment failure or re-infection; the treatment is typically repeated. WHO guidelines says that any presumed treatment failures at 4 weeks require macrolide resistance testing.
Yaws may be evolving less conspicuous lesions.Yaws is most common among children, who spread it by playing together. It is not thought to be transmitted from mother to child in the womb. Yaws is not a venereal disease.T. pallidum pertenue has been identified in nonhuman primates (baboons, chimpanzees, and gorillas) and experimental inoculation of human beings with a simian isolate causes yaws-like disease. However, no evidence exists of cross-transmission between human beings and primates, but more research is needed to discount the possibility of a yaws animal reservoir in nonhuman primates. Diagnosis
Most often the diagnosis is made clinically. Dark field microscopy of samples taken from early lesions (particularly ulcerative lesions) may show the responsible bacteria; the spirochaetes are only 0.3 µm wide by 6–20 µm long, so light-field microscopy does not suffice.A microscopic examination of a biopsy of a yaw may show skin with clear epidermal hyperplasia (a type of skin thickening) and papillomatosis (a type of surface irregularity), often with focal spongiosis (an accumulation of fluid in specific part of the epidermis). Immune system cells, neutrophils and plasma cells, accumulate in the skin, in densities that may cause microabscesses.Warthin–Starry or Levaditi silver stains selectively stain T. pallidum, and direct and indirect immunofluorescence and immunoperoxidase tests can detect polyclonal antibodies to T. pallidums. Histology often shows some spatial features which distinguish yaws from syphilis (syphilis is more likely to be found in the dermis, not the epidermis, and shows more endothelial cell proliferation and vascular obliteration).Blood-serum (serological) tests are increasingly done at the point of care.