Mapping the Epidemiology of Yaws in the Solomon Islands: A Cluster Randomized Survey

Abstract

Yaws, a non-venereal treponemal disease, is targeted for eradication by 2020 but accurate epidemiological data to guide control programs remain sparse. The Solomon Islands reports the second highest number of cases of yaws worldwide. We conducted a cluster randomized survey of yaws in two provinces of the Solomon Islands. One thousand four hundred and ninety-seven (1,497) children 5–14 years of age were examined. Clinical signs of active yaws were found in 79 children (5.5%), whereas 140 children (9.4%) had evidence of healed yaws lesions. Four hundred and seventy (470) (31.4%) children had a positive Treponema pallidum particle agglutination assay (TPPA). Two hundred and eighty-five (285) children (19%) had a positive TPPA and rapid plasma regain assay. Risk of yaws increased with age and was more common in males. The prevalence of yaws at village level was the major risk factor for infection. Our findings suggest the village, not the household, should be the unit of treatment in the World Health Organization (WHO) yaws eradication strategy.

Mathematical Modeling of Programmatic Requirements for Yaws Eradication

“…Estimates of the starting population for each compartment were derived from published population-based yaws prevalence studies ( 7 , 17 ). We modeled a discrete closed population without addition or reduction through births or deaths.…”

“…We estimated values for the rates of disease progression between different stages of yaws, including development of and relapse from latent yaws, by using expert opinion, published data, and estimates used in other models (Table 1) ( 1 , 14 , 17 ). We defined 3 transmission scenarios (low, medium, and high) by using published age-specific treponemal seroprevalence data ( 17 ), expert opinion, and values used in other yaws models ( 14 ).…”

“…We defined 3 transmission scenarios (low, medium, and high) by using published age-specific treponemal seroprevalence data ( 17 ), expert opinion, and values used in other yaws models ( 14 ). Based on these data, we calculated initial estimates of the number of new infections arising from a single index case in a fully susceptible population (the basic reproduction number [R 0 ]).…”

“…The mean R 0 taking account of the full structure of our model, including duration of infection and the size of each starting population, is 1.96, resulting in a mean R 0 of 1.45 (95% CI 1.01–2.14) for the low transmission settings, 1.95 (95% CI 1.38–2.91) for medium, and 2.47 (95% CI 1.7–3.68) for high transmission. We included a variable to represent the likelihood of a person receiving treatment for yaws in the absence of public health interventions based on published data ( 17 ). …”

Prevalence of soil-transmitted helminths in remote villages in East Kwaio, Solomon Islands

“…In a similar approach to eliminate yaws in rural Solomon Islands the village was proposed as the most effective unit rather than the family or region. 30 Acquisition of STH outside a resident's home village is possible, particularly from STH hot spots where eggs or larvae in faeces on the soil have grown to infective stages. 31-33 Hence, occasional low-level STH infection should be expected from outside the home village.…”