Impact of annual preventive mass chemotherapy for soil-transmitted helminths among primary school children in an endemic area of Gurage zone: a prospective cross-sectional study

Background and aim School-based preventive mass chemotherapy has been a key component of Ethiopia's national plan for the control of soil-transmitted helminths. Without an impact evaluation on the impact of a deworming program on infection levels, it is unclear whether the deworming program warrants levels of environmental transmission of infection. This study aimed to determine the impact of annual preventive mass chemotherapy for soil-transmitted helminths among schoolchildren in an endemic area of Gurage zone, south-central Ethiopia. Methods A repeated school-based quantitative prospective cross-sectional method was employed. Data were collected from study participants selected using systematic sampling with probability proportional to size at baseline and after annual treatment. Fresh stool samples were collected and processed using the Kato─Katz technique at the Wolkite University parasitology laboratory. SPSS-21 was used for data management and analysis. Changes in parasitological variables after treatment were estimated. Results Overall, 41.1% prevalence and 22.3% mean geometric infection-intensity reduction were found. Reductions in prevalence of Schistosoma mansoni and hookworms were 13.2% and 15.3%, respectively. Similarly, decreases in prevalence were seen in Ascaris lumbricoides and Trichuris trichiura, representing 94.4% and 80.0% reduction rates, respectively, while 25.9% of the children had heavy S. mansoni (≥400 eggs per gram) infections at baseline, which were reduced to 4.5% after annual treatment. Geometric mean infection intensity–reduction rates for hookworms, A. lumbricoides, and T. trichiura were 80.8%, 20.2%, and 96.7%, respectively. Conclusion Annual mass chemotherapy failed to clear soil-transmitted helminths completely in the present study. However, it resulted in a substantial reduction in overall prevalence and infection intensity. Therefore, other than deworming for school children, interventions such as access to improved personal hygiene and environmental hygiene in school should be emphasized to interrupt transmission.