Date Published: January 29, 2015
Publisher: Public Library of Science
Author(s): Rosanna Ghinai, Philip El-Duah, Kai-Hua Chi, Allan Pillay, Anthony W. Solomon, Robin L. Bailey, Nsiire Agana, David C. W. Mabey, Cheng-Yen Chen, Yaw Adu-Sarkodie, Michael Marks, Patrick J. Lammie. http://doi.org/10.1371/journal.pntd.0003496
Abstract: Yaws, caused by Treponema pallidum ssp. pertenue, is reportedly endemic in Ghana. Mass distribution of azithromycin is now the cornerstone of the WHO yaws eradication campaign. Mass distribution of azithromycin at a lower target dose was previously undertaken in two regions of Ghana for the control of trachoma. Ongoing reporting of yaws raises the possibility that resistance may have emerged in T. pallidum pertenue, or that alternative infections may be responsible for some of the reported cases. We conducted a cross-sectional survey in thirty communities in two districts of Ghana where MDA for trachoma had previously been conducted. Children aged 5–17 years with ulcerative lesions compatible with yaws were enrolled. Samples for treponemal serology and lesion PCR were collected from all children. 90 children with 98 lesions were enrolled. Syphilis serology was negative in all of them. PCR for T. pallidum ssp pertenue was negative in all children, but Haemophilus ducreyi DNA was detected in 9 lesions. In these communities, previously treated for trachoma, we found no evidence of ongoing transmission of yaws. H. ducreyi was associated with a proportion of skin lesions, but the majority of lesions remain unexplained. Integration of diagnostic testing into both pre and post-MDA surveillance systems is required to better inform yaws control programmes.
Partial Text: Yaws is a re-emerging endemic treponemal infection caused by Treponema pallidum ssp. pertenue . Early disease is characterised by papillomatous and ulcerative skin lesions, whilst late stage disease is characterised by skin lesions, bony involvement, and rarely progression to destructive lesions of the nasopharynx. Azithromycin (30mg/kg, maximum dose 2g) has recently been shown to be effective in the treatment of yaws and is now central to WHO’s yaws eradication strategy [2, 3]. Azithromycin is also key to the “SAFE” strategy for trachoma elimination. The target dose used in trachoma mass treatment (20mg/kg, maximum dose 1g) is lower than that demonstrated to be effective against yaws  although the delivered dose is frequently higher when a height based dosing strategy is used . Although resistance has yet to be documented in yaws, azithromycin resistance has emerged in other treponemal infections, notably syphilis [6–9]. The development of drug resistant T. pallidum ssp pertenue would have significant implications for yaws eradication ambitions.
Approximately 3,000 children from thirty communities were screened for inclusion in the study. 92 children (with a total of 100 moist ulcers) from a total of thirty communities were enrolled in the study. Two children (with one ulcer each) were later found to be ineligible (the first was over 18 years, and the second was from a community that did not undergo azithromycin MDA for trachoma), and were excluded from the results, leaving 90 children with a total of 98 moist ulcers. Many children had evidence of other skin problems but there was no evidence of typical papillomatous, palmar-plantar or macular lesions of primary or secondary yaws. The median age of enrolled children was 10 years (IQR 8 to 12 years), and 68 subjects (76%) were male. Thirty-seven children (41%) had not been born or were aged less than 1 at the time MDA was completed in their district (Table 1).
In this study conducted in the Northern Region of Ghana we found no evidence of active or latent yaws. All patients in this study had negative treponemal and non-treponemal serology. The fact that treponemal-specific serology was negative indicates that these individuals have never been infected with yaws. Both of the districts selected for this study had completed several rounds of azithromycin MDA for trachoma in the preceding decade. It is plausible that MDA for trachoma interrupted transmission of yaws resulting in its elimination in these districts and that these children, of whom about forty-percent never received MDA, have therefore never been exposed to yaws.