Worms at Work: Long-run Impacts of Child Health Gains from Deworming in Kenya
Intestinal worm infections—including hookworm, whipworm, roundworm and schistosomiasis—are among the world’s most widespread diseases, with roughly one in four people infected worldwide. Evidence indicates school-based deworming leads to large gains in school attendance and health outcomes in the medium term. This research measures the long-run impacts of deworming, approximately 10 years following treatment.
Intestinal worm infections—including hookworm, whipworm, roundworm and schistosomiasis—are among the world’s most widespread diseases, with roughly one in four people infected worldwide. School age children have the highest infection prevalence of any group, and while light worm infections are often asymptomatic, more intense infections can lead to lethargy, anemia, and growth stunting. There is a growing body of evidence that suggests that school-based deworming can generate immediate improvements in child appetite, growth, and overall health, and subsequent improvements in school attendance. However, in order to understand what level of public investment is worthwhile to support such public health measures, it is necessary to assess the long-run impacts of such programs.
This study is a follow-up of the Primary School Deworming Program (PSDP) that was launched by International Child Support (ICS) in Busia District in 1998. Busia district is a poor and densely-settled farming region in western Kenya adjacent to Lake Victoria. Budalangi and Funyula divisions have some of the country’s highest helminth infection rates, in part due to the area’s proximity to Lake Victoria—schistosomiasis is easily contracted through contact with the contaminated lake water. Soil-transmitted helminths (STH), on the other hand, are transmitted through contact with or ingestion of fecal matter. This can occur, for example, if children do not have access to a latrine and instead defecate in the fields near their home or school, where they also play. Surveys conducted by the Kenyan Ministry of health indicated that in 1998 this area had a helminth infection rate of over 90 percent.
A 2004 evaluation by J-PAL affiliates Edward Miguel and Michael Kremer evaluated the medium-run impacts of PSDP and found that the treatment led to large gains in school attendance and health outcomes. Due to the worms’ infectious nature, sizeable externality benefits also accrued to children who were not treated for worms but lived within treatment communities and near treatment schools. Seventy-five schools were randomly divided into three equal groups, which were phased into treatment over three years. Treatment schools with worm prevalence above 50 percent were given deworming drugs for geohelminths (albendazole) twice per year and for schistosomiasis (praziquantel) once per year (following World Health Organization (WHO) standards). Treatment individuals received two to three more years of deworming than the comparison group.
The first follow-up survey round of the PSDP sample, known as the Kenyan Life Panel Survey Round 1 (KLPS-1), was launched in 2003. Between 2003 and 2005, the KLPS-1 tracked a representative sample of approximately 7,500 individuals who had been enrolled in primary school grades 2-7 in the 75 PSDP schools at baseline in 1998. The second round of the Kenyan Life Panel Survey (KLPS-2), which tracked the same sample of individuals, was collected between 2007 and 2009. In addition to interviewing individuals still living in Busia District, survey enumerators traveled throughout Kenya and Uganda to interview those who had moved away. In total, 84 percent of original respondents who were still alive were successfully contacted for the follow-up survey.
Baird, Sarah, Joan Hamory Hicks, Michael Kremer, and Edward Miguel. "Worms at Work: Long-Run Impacts of a Child Health Investment." The Quarterly Journal of Economics (2016), 1637–1680..