Optimising the use of molecular tools for the diagnosis of yaws

Introduction Yaws is a neglected tropical disease and results in lesions of skin, soft tissues and bones. PCR plays an important part in surveillance. Methods Children suspected to have yaws were enrolled. From the largest lesion paired swabs were collected; one into transport medium and one as a dry swab. In children with multiple lesions we collected additional swabs from up to four subsequent lesions. Swabs in transport medium were maintained in a cold-chain whilst dry swabs were stored at ambient temperature. Swabs were tested by PCR for Treponema pallidum and Haemophilus ducreyi. Results Of 55 individuals, 10 (18%) had at least 1 positive PCR for T. pallidum and 12 (22%) had at least 1 positive result for H. ducreyi. Concordance was 100% between swabs in transport medium and dry swabs. One patient had PCR-confirmed yaws on the swab of a third lesion when both the first and second lesions were PCR-negative. Discussion Storing swabs in transport medium and transporting in a cold chain did not improve yield, however detection of T. pallidum is increased by swabbing additional lesions. As the target for yaws is eradication approaches to sample collection need revisiting to ensure cases are not missed.