title: Prevalence of Active and Latent Yaws in the Solomon Islands 18 Months after Azithromycin Mass Drug Administration for Trachoma.
abstract: Both yaws and trachoma are endemic in the Pacific. Mass treatment with azithromycin is the mainstay of the WHO strategy for both the eradication of yaws and the elimination of trachoma as a public health problem, but the dose recommended for trachoma is lower than that for yaws. In countries where both diseases are endemic, there is a potential for synergy between yaws and trachoma control programs if mass treatment with the lower dose of azithromycin was shown to be effective for the treatment of yaws. In an earlier study, we demonstrated a profound reduction in the clinical and serological prevalence of yaws following a single round of mass treatment with azithromycin 20 mg/kg undertaken for the purposes of trachoma elimination.
  
  
  
  This survey was conducted 18 months following a single round of azithromycin mass treatment in the same communities in which we had conducted our previous six-month follow-up survey. We examined children aged 1-14 years and took blood and lesion samples for yaws diagnosis using the Treponema pallidum particle agglutination assay (TPPA) and the non-treponemal Rapid Plasma Reagin (RPR) test.
  
  
  
  A total of 1,284 children were enrolled in the study. Amongst children aged 5-14 years, 223 had a positive TPPA (27.5%, 95% CI 13.6-47.7%). The TPPA seroprevalence amongst this age group did not differ significantly from either our pre-mass treatment survey or our initial follow-up survey. Thirty-five children had positive TPPA and positive RPR (4.3%, 95% CI 2.1-8.7%), and this did not differ significantly from our initial post-mass drug administration (MDA) follow-up survey (4.3% versus 3.5%, p = 0.43) but remained significantly lower than our initial pre-MDA survey (4.3% vs 21.7%, p <0.0001). Village-level MDA coverage was strongly associated with dual-seropositivity (p = 0.005). Amongst children aged 1-4 years, 16 had a positive TPPA (3.5%, 95% CI 1.6-7.1%). This did not differ significantly from the seroprevalence in this age group that had been predicted based on our previous surveys (3.5% vs 5%, p = 0.11). Fourteen children (1.1%) were considered to have a skin lesion clinically consistent with yaws, but none of these individuals was seropositive for yaws. Of nine cases where a swab could be collected for PCR, all were negative for Treponema pallidum subsp. pertenue DNA.
  
  
  
  In this study we have shown that the benefit of a single round of mass treatment with azithromycin 20mg/kg appears to extend to 18 months without any further intervention. The lack of a significant change in seroprevalence from 6 to 18 months after mass treatment might suggest that interventions could be spaced at yearly intervals without a significant loss of impact, and that this might facilitate integration of yaws eradication with other neglected tropical disease (NTD) control programmes. MDA coverage above 90% was associated with significantly better outcomes than coverages lower than this threshold, and strategies to improve coverage at all stages of yaws eradication efforts should be investigated.
authors.affiliation: Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom.|The Hospital for Tropical Diseases, London, United Kingdom.
authors.forename: Michael
authors.identifier: 0000-0002-7585-4743
authors.initials: M
authors.lastname: Marks
authors.affiliation: Ministry of Health and Medical Services, Honiara, Solomon Islands.
authors.forename: Oliver
authors.initials: O
authors.lastname: Sokana
authors.affiliation: Molecular Diagnostics & Typing Laboratory, Laboratory Reference & Research Branch, Division of STD Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
authors.forename: Eli
authors.initials: E
authors.lastname: Nachamkin
authors.affiliation: Ministry of Health and Medical Services, Honiara, Solomon Islands.
authors.forename: Elliot
authors.initials: E
authors.lastname: Puiahi
authors.affiliation: World Health Organization, Western Pacific Region Office, Honiara, Solomon Islands.
authors.forename: Georgina
authors.initials: G
authors.lastname: Kilua
authors.affiliation: Molecular Diagnostics & Typing Laboratory, Laboratory Reference & Research Branch, Division of STD Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
authors.forename: Allan
authors.initials: A
authors.lastname: Pillay
authors.affiliation: Department of Infectious Diseases Epidemiology, London School of Hygiene & Tropical Medicine, London, United Kingdom.
authors.forename: Christian
authors.initials: C
authors.lastname: Bottomley
authors.affiliation: Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom.|The Hospital for Tropical Diseases, London, United Kingdom.
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Solomon
authors.affiliation: Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom.|The Hospital for Tropical Diseases, London, United Kingdom.
authors.forename: David C
authors.initials: DC
authors.lastname: Mabey
mesh_terms: D000293:Adolescent; D000372:Agglutination Tests; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D017963:Azithromycin / Q000008:administration & dosage*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D016015:Logistic Models; D008297:Male; D008542:Melanesia / Q000453:epidemiology; D016036:Seroepidemiologic Studies; D014141:Trachoma / Q000188:drug therapy*; D014210:Treponema pallidum / Q000187:drug effects; D015001:Yaws / Q000175:diagnosis* / Q000517:prevention & control
chemical_list: D000900:Anti-Bacterial Agents; D017963:Azithromycin