This work was supported by grant OPPGH5342 from the Bill & Melinda Gates Foundation to Washington University. The Fiji and India studies were supported in part by the Coalition for Operational Research on Neglected Tropical Diseases (COR-NTD), which is funded at the Task Force for Global Health primarily by the Bill & Melinda Gates Foundation, by the United Kingdom Department for International Development, and by the United States Agency for International Development through its Neglected Tropical Diseases Program. Ivermectin was donated by Merck Sharp Dohme (MSD), also known as Merck & Co. (Kenilworth, NJ, USA), for all study sites except Fiji. Albendazole (produced and donated by GlaxoSmithKline) and diethylcarbamazine (DEC, produced and donated by Eisai Co.) were obtained from Ministry of Health stocks in each country.