Impact of Mass Drug Administration on Soil-Transmitted Helminth Infections Across Different Age Groups: A Retrospective Study From Southern Bihar.

BACKGROUND: Soil-transmitted helminth (STH) infections remain a major global public health concern, particularly in India. The Government of India has implemented mass drug administration (MDA) programs using albendazole to treat STH infections. However, the effectiveness of these deworming initiatives in reducing parasitic infections, particularly protozoal infections, remains incompletely characterized in many regions. METHODS: This retrospective observational study was conducted in the Department of Microbiology, Narayan Medical College and Hospital (NMCH), Sasaram, Bihar, India, from November 2023 to June 2025. The study included patients aged 1-84 years with documented prior albendazole deworming who underwent stool examination for suspected intestinal parasitic infections. Stool samples were processed using direct wet mount with saline and Lugol's iodine, and the salt flotation concentration method. Prevalence was calculated as frequencies and percentages. Fisher's exact test was used for comparisons among age groups using IBM SPSS Statistics version 28.0. Individual informed consent was waived, given the retrospective nature and use of anonymized laboratory records. RESULTS: Among 124 stool samples examined, 101 were included in the final analysis after excluding 23 samples for inadequate labeling, insufficient quantity, or missing demographic data. The mean age was 23.32 ± 5.42 years, with a male-to-female ratio of 1.59:1. Eight samples (7.9%) tested positive for parasitic infections: Giardia lamblia (n=6, 5.9%) and Entamoeba histolytica (n=2, 2.0%). No STH ova were detected. Ninety-three samples (92.1%) tested negative. Age-stratified analysis showed the highest parasitic prevalence in school-aged children (17.65%), followed by preschool-aged children (15.0%), with lower prevalence in adults (5.12%) and no infections in adolescents or the elderly. Fisher's exact test revealed no statistically significant difference in parasitic infection prevalence across age groups (P=0.175). CONCLUSION: The low prevalence of STH reflects the effectiveness of national MDA efforts and improved sanitation in southern Bihar. However, persistent protozoal infections despite prior deworming highlight the need for comprehensive water, sanitation, and hygiene (WASH) interventions and hygiene education to address protozoal transmission pathways not controlled by albendazole-based deworming programs.