• Intervention: Provides low-cost drugs to children in Kenya to eliminate parasitic worms.
  • Key Findings: Randomized controlled trial shows sizable positive impact on children’s health and school attendance.

In many developing countries, children are exposed to parasitic worms (e.g. hookworm, roundworm, schistosomiasis, and whipworm) when they swim in freshwater tainted with human fecal matter containing worms, or are exposed to raw sewage in areas where latrines are uncommon. Moderate to heavy infection with these worms causes serious health problems like anemia, and is a major reason why children in these developing countries miss school. Worldwide, four hundred million school-aged children are infected with worms, yet only 10 percent are being treated.

Description of the Intervention

In Kenya, Ministry of Health public health nurses visited schools and provided all boys and young girls with low-cost drugs ($0.49 per student per year) that eliminate worms. Girls of child-bearing age were not given drugs, as there is evidence that they may cause birth defects. All children were also provided hygiene education on topics like the importance of hand washing, wearing shoes, and not swimming in nearby lakes.


This program was evaluated in one randomized controlled trial of 75 schools in Busia, Kenya, a poor, densely-settled farming region near Lake Victoria (1998-2001). Schools were randomly assigned to intervention and control groups. Schools in the intervention group received free deworming treatment and hygiene education in 1998. To encourage schools to participate in the randomized controlled trial, the control schools were given the intervention at a later date, but received no treatment in 1998. Of the students in the intervention schools, 22% did not receive the treatment for a variety of reasons (e.g. absence from school on the days the drugs were provided).

Effects on schools that received the Primary School Deworming Project intervention at the one-year follow-up (versus the control schools):

The study found that the intervention had major positive impacts students’ health and school attendance outcomes at the one-year follow-up. Even the 22% of students in the intervention schools who did not receive the drug treatment showed benefits, because fewer worms were deposited in the general water supply. Specifically, the study reported the following impacts on all children in the intervention schools at the one year follow-up (including both those treated and those not treated).

  • 27 percent of children in the intervention schools had moderate or heavy infections with worms, compared to 52 percent in the control schools.
  • Children in the intervention schools had 7% higher height-for-age measures than children in the control schools.
  • There was no significant difference in weight-for-age measures between the two groups.
  • Children in the intervention schools had a 7-9% higher attendance rate than children in the control schools. This effect was greatest for the youngest children (preschool through grade 2) who had a 14% higher attendance rate than their control school counterparts.
  • There was no significant difference in achievement test scores between children in the intervention and control schools.
  • Teachers’ and children’s self-reports indicated that the hygiene education provided as part of this intervention had no effect on students’ behavior.

Discussion of Study Quality (click here for glossary of terms)

  • This was a large study with no sample attrition (i.e. outcome data were collected for all 75 schools).
  • The study reported outcomes using an intention-to-treat analysis.
  • The study used objective outcome measures: Biological testing was used to determine if children were infected with worms, and because official school attendance records were unreliable, outcome data on school attendance were gathered through three random, unannounced visits by program staff to each school.
  • Study Limitation: The study included only a one-year follow-up. Longer term follow-up is needed to determine whether the major positive effects reported at one year are sustained over time.


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