Schistosoma mansoni morbidity among school-aged children: a SCORE project in Kenya

Abstract

Schistosomiasis control programs aim to reduce morbidity but are evaluated by infection prevalence and intensity reduction. We present baseline cross-sectional data from a nested cohort study comparing indicators of morbidity for measuring program impact. Eight hundred twenty-two schoolchildren 7-8 years of age from Nyanza Province, Kenya, contributed stool for diagnosis of Schistosoma mansoni and soil-transmitted helminths (STH) and blood smears for malaria, and were evaluated for anemia, quality of life, exercise tolerance, anthropometry, and ultrasound abnormalities. Schistosoma mansoni, STH, and malaria infection prevalence were 69%, 25%, and 8%, respectively. Only anemia and S. mansoni infection (adjusted odds ratio [aOR] = 1.70; confidence interval [CI] = 1.03-2.80), and hepatomegaly and heavy S. mansoni infection (aOR = 2.21; CI = 1.19-4.11) were associated. Though anemia and hepatomegaly appeared most useful at baseline, additional morbidity indicators may be sensitive longitudinal measures to evaluate schistosomiasis program health impact.

Figure 1.

Parent Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) study design. Communities were randomized into six intervention arms. CWT = community-wide treatment; SBT = school-based treatment. Arms are sequentially numbered on the right side of the figure with Arm 1 being the top arm, and Arm 6 being the bottom arm.

Figure 2.

Numbers of children consented, enrolled, and included in the analysis. Light gray boxes to the right and left of the central pathway represent children excluded from the project and the reason for exclusion. The box in the bottom right of the figure indicates the inclusion criteria for the analysis.

Figure 3.

Proportion of children with anemia by intensity of Schistosoma mansoni infection. Gray bars represent the percent of children with anemia stratified by infection intensity. Whiskers above the bars represent 95% confidence intervals around the percent anemic. Numbers above the whiskers represent P values comparing the stratum value to the uninfected population.

Figure 4.

Proportion of children with hepatomegaly by intensity of Schistosoma mansoni infection. Gray bars represent the percent of children with hepatomegaly stratified by infection intensity. Whiskers above the bars represent 95% confidence intervals around the percent with hepatomegaly. Numbers above the whiskers represent P values comparing the stratum value to the uninfected population.