They get under your skin : Strongyloides stercoralis and hookworm distribution, risk profiling, and control in Cambodia

Abstract

Soil-transmitted helminths (STH) disproportionally affect the poorest and thrive in warm areas where sanitation conditions are poor. Infection with the threadworm, Strongyloides stercoralis, is among the most neglected tropical diseases and extremely common in Cambodia. A national control strategy for this parasite has not yet been defined. The aim of this PhD study was to contribute to the knowledge-base that will guide S. stercoralis control efforts in Cambodia, by documenting post-treatment reinfection risk and morbidity associated with infection, and by estimating the national prevalence of the parasite and assessing its geographical distribution across the country. Secondary objectives included profiling hookworm infection risk in the region, either alone or in concurrence with S. stercoralis. The study found that about one third of the Cambodian population was infected with S. stercoralis. Importantly, we found that chemotherapy-based control of S. stercoralis using ivermectin was feasible and highly beneficial, and its impact was enhanced by improved sanitation. Treatment resolved dermatological and gastrointestinal symptoms in infected patients. The cost of ivermectin in Cambodia currently prevents the roll-out of control programmes. Ivermectin donation, subsidization, or the production of affordable generics are urgently needed so that control can be implemented without further delay.