Worms: Education and Health Externalities in Kenya

Intestinal helminths - including hookworm, roundworm, schistosomiasis, and whipworm - infect more than one-quarter of the world's population. A randomized evaluation of a project in Kenya suggests that school-based mass treatment with deworming drugs reduced school absenteeism in treatment schools by one quarter; gains are especially large among the youngest children. Deworming is found to be cheaper than alternative ways of boosting school participation. By reducing disease transmission, deworming creates substantial externality health and school participation benefits among untreated children in the treatment schools and among children in neighboring schools. These externalities are large enough to justify fully subsidizing treatment. We do not find evidence that deworming improves academic test scores. Existing experimental studies, in which treatment is randomized among individuals in the same school, find small and insignificant deworming treatment effects on education; however, these studies underestimate true treatment effects if deworming creates positive externalities for the control group and reduces treatment group attrition.