Follow-up Assessment of Change in Soil-transmitted Helminths Infection Intensity in Uganda

The goal of this prospective follow-up study nested within an open-label randomized controlled trial is to investigate the unexpectedly high prevalence of Ascaris lumbricoides infection observed 3-4 months after school-based mass drug administration with ivermectin plus albendazole (IVM-ALB) or albendazole alone (ALB) in Kisoro District, South-Western Uganda. By assessing initial treatment response and subsequent infection dynamics, the study will help clarify whether reduced drug efficacy, suboptimal treatment coverage, reinfection, or a combination of these factors may explain the previous findings. The main questions the study aims to answer are: * How effective are IVM-ALB and ALB against A. lumbricoides at 3 weeks, based on egg reduction and cure rates? * How often do A. lumbricoides and other soil-transmitted helminth infections recur by 3 months? * How effective are the treatments against Trichuris trichiura and hookworm? * What can genetic characterization of Ascaris eggs reveal about parasite populations and potential drug resistance markers? The study will enrol 450 pupils aged 5-14 years from three primary schools, which participated in the previous mass drug administration evaluation. In each school, 150 pupils will be randomly assigned equally to receive a single oral dose of: * ivermectin (200 µg/kg) plus albendazole (400 mg); or * albendazole (400 mg) alone. Each treatment arm will include 225 pupils overall. Children will be included regardless of baseline infection status, following parental/guardian informed consent and child assent. Other pupils will receive routine albendazole under national deworming guidelines. Stool samples will be collected before treatment and at 3 weeks and 3 months. Duplicate Kato-Katz thick smears will quantify A. lumbricoides, T. trichiura and hookworm eggs. The primary outcome is the arithmetic mean egg reduction rate for A. lumbricoides at 3 weeks. Secondary outcomes include cure rates at 3 weeks, reinfection rates at 3 months, egg reduction and cure rates for T. trichiura and hookworm, and genetic characterization of Ascaris populations and potential resistance markers. Adverse events will be recorded through passive safety monitoring.

Inclusion Criteria: * Informed consent provided by parent/guardian and assent provided by pupil * School-aged children (5-14 years) enrolled in the respective study schools * Able and willing to provide a stool sample before and 3 weeks and 3 months post-treatment Exclusion Criteria: * Presence or signs of major systemic illness * Recent use of anthelmintic drugs in the 4 weeks before treatment * Known allergy to study medication (i.e. benzimidazoles or ivermectin) * Participation in other clinical trials