Absence of human yaws and detection of Haemophilus ducreyi in skin ulcers of school children near wildlife protected areas in Tanzania

Background To support Tanzania’s quest for certification free of human yaws, we tested children with skin ulcers for yaws infection living near areas of reported nonhuman primate (NHP) infection with Treponema pallidum subsp. pertenue ( TPE ). The study also aimed to test children for infection with Haemophilus ducreyi ( HD ), the most common differential diagnosis for yaws. Methodology/principal findings A cross-sectional design was used to study primary school children with skin ulcers living near wildlife areas with TPE infected NHPs. Serum and ulcer swab samples were collected from the children. Serum samples were tested for anti- T . pallidum antibodies using treponemal (Particle Agglutination Assay) and non-treponemal (Rapid Plasma Reagin) tests. Ulcer swab samples were tested by quantitative PCR (qPCR) for the presence of TPE and HD bacteria. 612 children were recruited from 56 primary schools between August 2018 and February 2019. The mean age ± SD was 10.3 ± 2.3 and 10.7 ± 2.4 years for girls and boys, respectively. While none of the tested children had treponemal or non-treponemal antibodies, 21 (5.3%, 95% CI = 3.5% - 7.9%) were tested positive for HD by qPCR. Only strains that fall into the HD genotype class I were detected. Conclusions/significance We show that human yaws infection is likely interrupted in the study areas, although the yaws bacterium is still circulating in NHPs. Due to the potential zoonotic nature of NHP-infecting strains, continued surveillance is needed for yaws and HD infection. Here, we provide the first data on HD associated (non-genital) skin lesions in Tanzanian children.