Early life exposures of enteric pathogens and nutritional outcomes in Timor-Leste: a longitudinal birth cohort study protocol

Introduction Child undernutrition remains a major public health problem in low- and middle-income countries. Timor-Leste has one of the highest childhood stunting rates worldwide, affecting an estimated 47% of children under 5 years. Repeated exposure to enteric pathogens is increasingly recognised as a contributor to malnutrition, yet the interplay between enteric infection, environmental exposure and socioeconomic factors remains poorly understood in this setting. This protocol describes a longitudinal birth cohort study, conducted within a One Health framework, examining early-life enteric pathogen exposure and its relationship with nutritional outcomes in Timor-Leste.Methods and analysis This mixed-methods longitudinal birth cohort study, part of the Bacteria, Enteropathy and Nutrition research programme, is being conducted in three municipalities of Timor-Leste (Dili, Ermera and Ainaro) from November 2024 to October 2027. We will recruit 450 infants at birth and follow them for 24 months, with home visits at 3 monthly intervals in year 1 and 6 monthly intervals in year 2. Faecal, food, water, soil and domestic animal samples will be tested for bacterial, viral and parasitic pathogens; child growth will be assessed using anthropometry. Structured surveys, household observations and in-depth interviews will capture food safety practices, feeding behaviours and socioeconomic factors. Associations between enteric infection and child growth will be assessed using multivariable regression and longitudinal mixed-effects models; qualitative data will be analysed thematically.Ethics and dissemination Ethical approval has been granted by the Human Research Ethics Committee and Veterinary Research Ethics Committee of the Ministry of Health, Timor-Leste (1827/INSP-TL/UEPD-AL/X/2024), Menzies School of Health Research (EC00153) and the Australian National University (H/2024/0964). Written informed consent will be obtained from parents or guardians. Findings will be disseminated through peer-reviewed publications, conference presentations, community workshops and policy briefs in English and Tetum.