Unprogrammed Deworming in the Kibera Slum, Nairobi: Implications for Control of Soil-Transmitted Helminthiases

Improper disposal of human feces contaminated with helminth eggs exposes humans to infection following ingestion of eggs or skin contact with larvae that hatch from eggs. A wide array of physical effects have been attributed to intestinal STH infections, including anemia, anemia caused by hookworm infection, and intestinal obstruction. Morbidity is directly related to infection intensity. The World Health Organization recommends reduction of worm burden in individuals rather than elimination. In 2001, WHO set the goal of providing regular deworming chemotherapy to at least 75% of at-risk school-aged children by 2010. Pharmaceutical companies agreed to donate billions of doses of antihelminthic drugs to countries in need, enabling the expansion of existing deworming programs. Many STH-endemic countries, including Kenya, are now planning or actively implementing national school-based deworming programs. In Kenya, a phased-in approach to school-based deworming was planned for selected districts, excluding Nairobi, Rift Valley, and North East Provinces. However, small-scale deworming programs are also frequently carried out by in-country partners, who may use different regimens for deworming. Deworming drugs are widely available from clinics, drugstores, and other sources, leading to unprogrammed deworming, which is deworming outside of the context of nationally-administered STH control programs. Unprogrammed deworming is a significant concern, as it is frequently neither documented nor reported to health officials. Accurate reporting of deworming is required to monitor progress towards the WHO treatment targets for 2020. In Kibera, an urban slum in Nairobi, Kenya, unprogrammed deworming was received by more than half of children, from multiple sources, including chemists, healthcare centers, and schools. The study in Kibera found that more than half of school-aged and preschool-aged children received deworming medications outside of a national school-based deworming program. These drugs were received from multiple sources, including chemists, healthcare centers, and schools, via efforts of non-governmental organizations. The data indicate a need to collect information on all sources of deworming medications when evaluating the effectiveness of national school-based deworming programs. The study also found that unprogrammed deworming was negatively associated with any-STH infection. School-aged children whose most recent deworming medication was obtained from a chemist were more often infected with Trichuris than those who received their most recent treatment from a health center or school. The study suggests that unprogrammed deworming may serve an important public health function, particularly in the absence of programmed deworming, but may also lead to overestimation of programmed MDA effectiveness. A validated tool is needed to assess unprogrammed deworming. The study highlights the need for accurate reporting of deworming to monitor progress towards the WHO treatment targets for 2020. The findings of the study have implications for the evaluation of national school-based deworming programs and the control of soil-transmitted helminthiases.