Zoonotic tuberculosis in nomadic pastoral communities in Nigeria: Risk routes for transmission, socio-cultural drivers and public health implications

Abstract

Background: Bovine tuberculosis (bTB) is a zoonotic disease, caused by Mycobacterium bovis, a member of Mycobacterium tuberculosis complex. M. bovis causes 5–7% of human tuberculosis cases in Africa. To achieve the World Health Organization's “END-TB” goal by 2035, surveillance system that encompasses livestock herders’ knowledge about bTB epidemiology is required. Study objectives were: to assess pastoralists’ knowledge-attitude-practices regarding bTB, zoonotic transmission risk routes, and estimate its prevalence in lactating pastoral cow herds. We hypothesized that socio-cultural practices cannot influence bTB occurrence in pastoral communities. Methods and materials: Interview-questionnaire based cross-sectional study was conducted on 600 randomly selected herd owners in nomadic pastoral communities of north-central Nigeria in 2018. Also, 196 lactating Zebu cows were systematic randomly selected for raw milk collection in targeted herds. Milk samples were examined for acid-fast bacilli using Ziehl-Neelsen microscopic evaluation in a biosafety laboratory level II. Descriptive, unvariate and multivariable logistic regressions models were performed at 95% confidence level. Results: An 8.7% (11/196) prevalence of red rod-like tubercle bacilli was obtained. About 90% (538/600) of selected pastoralists participated. Majority (63.9%) of respondents had no formal education. Only 24.7% of them mentioned bTB to be zoonotic. Only 18.8% of participants practiced adequate boiling of raw milk before consumption as preventive measures. Risk routes for bTB zoonotic transmission were: consumption of raw milk and milk products (p < 0.001); contacts with infected udder and co-habitation with infected cows (p = 0.001); and aerosols of milk with viable M. bovis during milking and discarded infected milk in the environment (p < 0.001). Socio-cultural drivers associated with zoonotic tuberculosis occurrence in nomadic pastoral communities were: extensive husbandry system (p < 0.001), culture of borrowing/loaning cattle (p = 0.001), culture of giving out cattle as gift/payment for dowry (p = 0.001), high herds density sharing common watering points (p < 0.001) and introduction of new cattle into herd without quarantine (p = 0.001). Conclusion: This study revealed pastoralists’ low knowledge and practices regarding zoonotic tuberculosis. The challenging gaps call for health education of vulnerable populations. Tuberculosis surveillance and control programmes take identified bTB risk transmission routes and social drivers into consideration, in line with ‘One Health’ approach, will assure food safety, food security, public and environmental health in Africa.