Background: In small community-based trials, ivermectin mass drug administration (MDA) has been shown to substantially reduce prevalence of both scabies and secondary impetigo. The effect at larger scale has not been measured. We aimed to investigate the efficacy of the intervention against community prevalence of scabies and impetigo.
Methods: The Azithromycin Ivermectin MDA (AIM) trial was a prospective, single-arm, before-and-after, community intervention trial to assess the efficacy of ivermectin and azithromycin MDA for scabies and impetigo. MDA was offered to the entire population of Choiseul Province, Solomon Islands. We compared prevalence of scabies and impetigo in residents of 10 randomly-selected villages at baseline, to that in residents of 10 different randomly-selected villages 12 months after MDA. Randomisation included selecting settlements with populations between 100 and 250. We also compared the number of outpatient presentations before and after MDA.
Findings In September 2015, 26,188 people (99·3% of the estimated resident population of Choiseul) were treated. Skin examination was performed in 1,399 people at baseline (84·2% of the estimated resident population of selected villages) and 1,261 people (77·6%) 12 months after MDA. At baseline there were 261 people (18·7%) with scabies and 347 people (24·8%) with impetigo. At 12 months there were 29 people (2·3%) with scabies (relative reduction 88%, 95%CI 76·5–99·3 and 81(6·4%) with impetigo (relative reduction 74%, 95%CI 63·4–84·7) respectively. There were 10,614 presentations to outpatient clinics in the three-months after MDA compared to 16,602 in the three-months before. (36·1% reduction, 95%CI 34·7-37·6). Skin sores, boils and abscesses presentations fell by 50·9% (95%CI 48·6–53·1).
Interpretation: Ivermectin-based MDA is scalable in populations over 25,000 with a similar efficacy for scabies and impetigo as in smaller island populations, and this level of efficacy can be achieved when MDA for scabies is integrated with azithromycin MDA for trachoma.