Scabies prevalence after ivermectin-based mass drug administration for lymphatic filariasis, Samoa 2018–2019.

Background: Scabies is a common skin infestation caused by the Sarcoptes scabei mite. Ivermectin, one of three drugs used in mass drug administration (MDA) for lymphatic filariasis, is also effective for treating scabies. Ivermectin-based MDA was first conducted in Samoa in August 2018, with ivermectin being offered to those aged ≥5 years. Here, we report scabies prevalence in Samoa after MDA. Methods: We conducted household surveys 1.5–3.5 months (Survey 1) and 6–8 months (Survey 2) after the 2018 MDA in 35 primary sampling units. We conducted clinical examination for scabies-like rash and used International Alliance for the Control of Scabies classification criteria. We estimated scabies prevalence by age, gender and region. Multivariable logistic regression was used to assess factors associated with prevalence. Results: We surveyed 2868 people (499 households) and 2796 people (544 households) aged 0–75 years in Surveys 1 and 2, respectively. Scabies prevalence increased from 2.4% (95% CI 2.1–2.7%) to 4.4% (95% CI 4.0–4.9%) between surveys. Scabies was associated with younger age (0–4 years: aOR 3.5 [2.9–4.2]; 5–15 years: aOR 1.6 [1.4–1.8] compared to ≥16 years), female gender (aOR 1.2 [95% CI 1.1–1.4]; region (aOR range from 1.4 [1.1–1.7] to 2.5 [2.1–3.1] between regions), large households (aOR 2.6 [2.0–3.4] households ≥13), and not taking MDA in 2018 (aOR 1.3 [95% CI 1.1–1.6]). Conclusions: We found moderate prevalence of scabies in two population-representative surveys conducted within 8 months of the 2018 MDA for lymphatic filariasis. Prevalence appeared to increase between the surveys, and ongoing surveillance is recommended, particularly in young children. Author summary: Scabies is a common skin disease that is caused by a small mite that burrows into the skin. It can be treated by a drug called ivermectin, which was given to every person aged 5 years and over in Samoa in 2018 to treat a different disease, known as lymphatic filariasis. We wanted to understand how common scabies was in the people of Samoa and so did two surveys where we visited people's houses that we randomly selected. We and asked people in each household questions about scabies symptoms and looked at their skin for signs of scabies. We surveyed 2868 people in 499 households in the first survey and 2796 in 544 households in the second survey. We found that 2.4% of people in the first survey and 4.4% of people in the second survey had scabies. We also found that some people were more likely to have scabies: younger children, women, people living in some regions of Samoa, people living with more people in their household, and people who didn't take the medicine for lymphatic filariasis in 2018. [ABSTRACT FROM AUTHOR]