Ulcerative skin lesions among children in Cameroon: It is not always Yaws
Authors: Ngono Jean-Philippe Ndzomo , Tchatchouang Serges , Tsanga Mireille Victorine Noah , Tabah Earnest Njih , Tchualeu Albert , Asiedu Kingsley , Giacani Lorenzo , Eyangoh Sara , Crucitti Tania 
Published: August 2020

Outbreaks of yaws-like ulcerative skin lesions in children are frequently reported in tropical and sub-tropical countries. The origin of these lesions might be primarily traumatic or infectious; in the latter case, Treponema pallidum subspecies pertenue, the yaws agent, and Haemophilus ducreyi, the agent of chancroid, are two pathogens commonly associated with the aetiology of skin ulcers. In this work, we investigated the presence of T. p. pertenue and H. ducreyi DNA in skin ulcers in children living in yaws-endemic regions in Cameroon.

Skin ulcer swabs were collected from children presenting with yaws-suspected skin lesions during three outbreaks, two of which occurred in 2017 and one in 2019. DNA extracted from the swabs was used to amplify three target genes: the human β2-microglobulin gene to confirm proper sample collection and DNA extraction, the polA gene, highly conserved among all subspecies of T. pallidum, and the hddA gene of H. ducreyi. A fourth target, the tprL gene was used to differentiate T. p. pertenue from the other agents of human treponematoses in polA-positive samples.

A total of 112 samples were analysed in this study. One sample, negative for β2-microglobulin, was excluded from further analysis. T. p. pertenue was only detected in the samples collected during the first 2017 outbreak (12/74, 16.2%). In contrast, H. ducreyi DNA could be amplified from samples from all three outbreaks (outbreak 1: 27/74, 36.5%; outbreak 2: 17/24, 70.8%; outbreak 3: 11/13, 84.6%).

Our results suggest that H. ducreyi might be more frequently associated to skin ulcers in the examined children than T. p. pertenue, but shows nonetheless that yaws is still present in Cameroon. These findings strongly advocate for a continuous effort to determine the aetiology of ulcerative skin lesions during these recurring outbreaks, and to inform the planned mass treatment campaigns to eliminate yaws in Cameroon.

Author summary

Yaws caused by Treponema pallidum pertenue is one of the most prevalent skin ulcer diseases among children in tropical and sub-tropical countries in Africa and the South-Pacific region. In Cameroon, outbreaks of yaws occur among populations living in remote areas where health infrastructure is lacking. The diagnosis is frequently made clinically, but currently rapid and simple serological assays were introduced to confirm active yaws infection. Lately, studies using molecular amplification assays and performed in the South Pacific and Ghana reported that apart from T. p. pertenue, Haemophiluys ducreyi is also detected in children presenting with yaws-like lesions. This study was performed in the context of the surveillance of yaws in the East and South region of Cameroon. Molecular tools were used to detect and confirm the presence T. p. pertenue in samples suspected of yaws and collected during three outbreaks of ulcerative skin lesions among children in Cameroon. In addition all samples were analysed for H. ducreyi. We found that H. ducreyi was present in samples from all three outbreaks, but T. p. pertenue was only detected among samples collected during the first outbreak. We confirmed that yaws was present in Cameroun but that not all outbreaks of yaws like skin lesions were attributable to T. p. pertenue infection.