Quantitative Risk Assessment of Bovine Tuberculosis Transmission to Humans Through Dairy Consumption in Pastoralist Systems in North West Nigeria

Bovine tuberculosis caused by Mycobacterium bovis transmitted through unpasteurized dairy products remains a significant public health risk in pastoralist systems, yet quantitative risk estimates specific to Nigerian settings are absent. This study conducted a quantitative risk assessment of Mycobacterium bovis transmission to humans through dairy product consumption in pastoralist communities in Zamfara, Katsina, and Sokoto States, North West Nigeria. A stochastic farm-to-consumer risk assessment model was constructed. Inputs included bovine tuberculosis prevalence data from tuberculin skin testing of 500 cattle, milk contamination probabilities estimated from literature and primary culture data, dairy processing and consumption practices from 400 household surveys, and dose-response relationships from published human infection studies. Monte Carlo simulation with 100,000 iterations was used to propagate uncertainty. The model estimated an annual probability of Mycobacterium bovis infection through dairy consumption of 1.4 per 1,000 individuals in high-exposure pastoral households. Sensitivity analysis identified bovine tuberculosis prevalence and raw milk consumption frequency as the two highest-impact variables. Pasteurization scenarios reduced estimated risk by 97%. Child consumers under five years showed three times the risk of adult household members. The study presents the first quantitative risk estimate for Mycobacterium bovis dairy transmission in North West Nigerian pastoralism and contributes a methodological framework applicable to analogous systems across West Africa. Targeted pasteurization promotion and cattle test-and-cull compensation programs are recommended as primary risk mitigation strategies. Keywords: bovine tuberculosis, quantitative risk assessment, dairy transmission, pastoralism, North West Nigeria