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Primary School Deworming in Kenya

Intestinal helminths—including hookworm, roundworm, whipworm, and schistosomiasis—infect more than one-quarter of the world’s population. Researchers evaluated a mass school-based deworming program in Western Kenya, and found that the program reduced school absenteeism in treatment schools by one-quarter, and was far cheaper than alternative ways of boosting school participation. Deworming also substantially improved health and school participation among untreated children in both treatment schools and neighboring schools.

Policy Issue 

Intestinal helminthsincluding hookworm, roundworm, schistosomiasis and whipworminfect more than one in four people worldwide and are particularly prevalent among school-aged children in developing countries. These intestinal worms are believed to have a negative impact on education, hindering child development as well as school attendance and reducing income later in life. These effects are especially pronounced in Africa, where nearly half of the total disease burden is due to infectious and parasitic diseases, including helminth infections. Existing randomized studies have focused primarily on the effects that these diseases have on cognitive performance, whereas outcomes of more direct interest to economists and policymakersschool attendance and enrollment, test scores, and ultimately, labor market outcomeshave yet to be thoroughly investigated.

Context of the Evaluation 

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 Victoriaschistosomiasis 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. One quarter of Kenyan student absenteeism is attributed to abdominal pains that are likely due to intestinal helminth infections. In addition, older children may miss school to take care of siblings who are sick with helminth infections.

Details of the Intervention 

This study evaluated the Primary School Deworming Project (PSDP), which was carried out by International Child Support in cooperation with the Busia District Ministry of Health. The program randomly divided 75 schools into three equal groups, which were phased into treatment over three years.

Within each group, a baseline parasitological survey was administered to a random sample of pupils. Schools with worm prevalence over 50 percent were mass treated with deworming drugs every six months. Girls of reproductive age (thirteen and older) were not supposed to be treated due to concerns about the possibility of birth defects. Nonetheless, 19 percent of girls thirteen and older also received medical treatment, partly due to confusion about pupil age, and partly because several Kenyan public health nurses administered drugs to some older girls, judging the benefits to outweigh the risks. In addition to medicine, treatment schools received regular public health lectures, wall charts on worm prevention, and training for one designated teacher. The lectures and teacher training provided information on worm prevention behaviors, including washing hands before meals, wearing shoes, and not swimming in the lake.

Results and Policy Lessons 

Impact on Infection Intensity: Deworming reduced moderate to heavy helminth infections by 25 percentage points (61 percent) amongst children in the treatment groups. Pupils that received treatment reported being sick less often, and they had significantly better height-for-agea measure of nutritional status. Health education had minimal impact on worm prevention behaviors, including observed pupil cleanliness, the proportion of pupils wearing shoes, or self-reported exposure to fresh water. Therefore, to the extent that the program improved health, it almost certainly did so through the effect of the medicines rather than through health education.

Impact on School Attendance and Test Scores: Deworming increased school participation by at least 7 percentage points, which is equivalent to a one-quarter reduction in school absenteeism. Among girls younger than thirteen years old and all boys who were treated, school participation in the first year after medical treatment increased by 9.3 percentage points relative to the comparison group. This is consistent with the fact that a much smaller proportion of older girls actually received medical treatment. No improvements in test scores were found as a result of the deworming.

Treatment Spillover: Those living up to 6 kilometers away from treatment schools benefited from "spillovers" of the deworming treatment. Spillover effects occur because medical treatment reduces the transmission of infections to other community members. It is estimated that moderate-to-heavy helminth infections among children living up to 6 kilometers away from treatment schools were 23 percentage points lower on average.

Cost-Effectiveness: Including the spillover benefits of treatment, the cost per additional year of school participation was US$3.50, making deworming considerably more cost-effective than alternative methods of increasing school participation, such as school subsidies.

Miguel, Edward, and Michael Kremer. 2004. "Worms: Identifying Impacts on Education and Health in the Presence of Treatment Externalities." Econometrica 72(1): 159-217.