Deworming: A Best Buy for Development

This Bulletin describes the lessons from a series of studies evaluating the Primary School Deworming Project (PSDP), a school-based deworming program run in western Kenya between 1998 and 2001. These studies form one of the first long-term evaluations of a health and education intervention in a developing country. The verdict from this body of evidence is clear: deworming treatment is not only highly effective and inexpensive, it is easy to administer through public schools and brings benefits to children years after treatment.

Deworming treatment improved health and reduced absenteeism. Among children in the treatment schools, moderate-to-heavy worm infections decreased dramatically, and other health indicators, such as anemia and self-reported illness, improved. Deworming increased the attendance rate by 7.5 percentage points at treatment schools. Even untreated children benefited from deworming. Children who attended comparison schools that were physically close to treatment schools also experienced fewer worm infections and higher school attendance.

Deworming improved cognitive outcomes for infants who were not treated directly. A decade later, children who had been infants when the deworming program started in their community showed cognitive gains equivalent to 0.5–0.8 years of schooling. Treated students continued to benefit a decade after the program. Young adults who had more exposure to deworming treatment as children worked more hours and ate more meals per day. Among those who worked for wages, adults who had more exposure to deworming treatment earned over 20 percent more.