Haemophilus ducreyi Associated with Skin Ulcers among Children, Solomon Islands

During a survey of yaws prevalence in the Solomon Islands, we collected samples from skin ulcers of 41 children.Using PCR, we identified Haemophilus ducreyi infection in 13 (32%) children.PCR-positive and PCR-negative ulcers were phenotypically indistinguishable.Emergence of H. ducreyi as a cause of nongenital ulcers may affect the World Health Organization's yaws eradication program.B acterial ulcerative skin diseases are a common cause of illness in the developing world (1).Some of these diseases, including Buruli ulcer, caused by Mycobacterium ulcerans, and yaws, caused by Treponema pallidum subspecies pertenue, occur only in tropical and subtropical climates.Yaws is endemic in the Solomon Islands, where ≈15,000 cases per year are reported (2).In 2012, the World Health Organization (WHO) launched a worldwide yaws eradication program based on treatment by mass distribution of azithromycin and monitoring for skin ulcers (3).Reports suggest that Haemophilus ducreyi, the causative organism of chancroid, a sexually transmitted infection, may be associated with nonsexual transmission of nongenital ulcers of the skin in persons from the Pacific region (4,5).If this organism is a common cause of skin ulcers in the region, this factor has crucial implications for the yaws eradication strategy.PCR has been shown to be highly sensitive and specific for diagnosing chancroid (6).We used real-time PCR to detect H. ducreyi in skin ulcer samples collected during a survey for yaws in the Solomon Islands. The StudyWe conducted a cross-sectional survey for yaws in the Western Province and Choiseul Province of the Solomon Islands in 2013.In each province, we chose 25 clusters using a probability-proportionate-to-size method.In each cluster, we selected 30 houses by random sampling; children 5 to 14 years of age living in those houses were invited to participate.Informed written consent was obtained from the children's parents.Children underwent standardized examination.We recorded location, classification, and duration of skin lesions and yaws treatment history using the LINKS system (7, http://www.linkssystem.org/).Lesions were classified by using the WHO pictorial grading scheme for yaws (8).Tenderness was classified based on reports by children.Blood samples were collected from all children.For children with exudative skin lesions, a sample for PCR was collected by rolling a sterile cotton-tipped swab across the lesion and placing it in a cryotube pre-filled with 1.2 mL of AssayAssure solution (Thermo Fisher Scientific, Waltham, MA, USA).Samples were transferred to Honiara National Referral Hospital within 5 days and stored at -20°C.Serum samples were placed on dry ice and shipped to the London School of Hygiene & Tropical Medicine and lesion samples to the US Centers for Disease Control and Prevention.Serum samples were tested by using T. pallidum particle agglutination (Mast Diagnostics, Merseyside, UK) at the London School of Hygiene & Tropical Medicine.For samples with a positive T. pallidum particle agglutination, a rapid plasma regain test was performed (Deben Diagnostics, Ipswich, UK).DNA was extracted from lesion samples in a CDC laboratory by using iPrep PureLink gDNA blood kits and the iPrep purification instrument (Life Technologies, Grand Island, NY, USA).A real-time duplex PCR targeting the DNA polymerase I gene (polA, tp0105) of pathogenic treponemes (which detects all 3 T. pallidum subspecies) and the human RNase P gene (to monitor for PCR inhibition) was performed by using a Rotor-Gene-Q real-time PCR instrument (QIAGEN Inc., Valencia, CA, USA) (9).Negative (no-template) control and positive controls for T. pallidum DNA were included in each PCR run.Considering reports of H. ducreyi and the occurrence of M. ulcerans in Papua New Guinea, immediately north of the Solomon Islands, we performed a second duplex real-time PCR for M. ulcerans and H. ducreyi on all samples by using previously validated targets (10,11).For the purpose of analysis, lesions were classified as acute (<4 weeks) or chronic (>4 weeks).A rapid plasma regain titer ≥1/4 was considered positive.Fisher exact test was used to compare characteristics of patients whose lesions contained H. ducreyi with patients whose lesions did not contain H. ducreyi.Analyses were performed by using STATA 13.1 (http://www.stata.com/).