Background
The implementation of soil-transmitted helminth (STH) treatment programmes occurs in
varied environmental, social and economic contexts. Programme impact will be influenced
by factors that affect the reduction in the prevalence and intensity of infections following
treatment, as well as the subsequent rate of reinfection. To better understand the heterogeneity
of programme impact and its underlying reasons, we investigated the influence of contextual
factors on reduction in STH infection as part of the national school based deworming
(SBD) programme in Kenya.
Materials and Methods
Data on the prevalence and intensity of infection were collected within the monitoring and
evaluation component of the SBD programme at baseline and after delivery of two annual
treatment rounds in 153 schools in western Kenya. Using a framework that considers STH
epidemiology and transmission dynamics, capacity to deliver treatment, operational feasibility
and financial capacity, data were assembled at both school and district (county) levels.
Geographic heterogeneity of programme impact was assessed by descriptive and spatial
analyses. Factors associated with absolute reductions of Ascaris lumbricoides and hookworm infection prevalence and intensity were identified using mixed effects linear
regression modelling adjusting for baseline infection levels.
Principal Findings
The reduction in prevalence and intensity of A. lumbricoides and hookworms varied significantly
by county and within counties by school. Multivariable analysis of factors associated
with programme impact showed that absolute A. lumbricoides reductions varied by environmental
conditions and access to improved sanitation at schools or within the community.
Larger reduction in prevalence and intensity of hookworms were found in schools located
within areas with higher community level access to improved sanitation and within counties
with higher economic and health service delivery indicator scores.
Conclusions
The study identifies factors associated with the impact of school-based deworming and in
particular highlights how access to water, sanitation and hygiene and environmental conditions
influence the impact of deworming programmes.