Burden of Bovine Tuberculosis on Animal Health, Welfare and Production: A Systematic Review.

Developing evidence-based approaches to combat infectious diseases is essential in resource-limited settings to enable prioritisation of interventions where they are most effective in reducing the burden of disease. Bovine tuberculosis (bTB) is a major disease in cattle, but its impact remains poorly characterised in many contexts and production systems. To support the development of policies for accelerated bTB control, we conducted a systematic review to collate the available evidence on the impact of bTB on animal health, welfare and production. We identified 91 eligible studies providing information on the burden of bTB. Although the study suggested that bTB poses a considerable burden, the data were sparse and occasionally contradictory. A large proportion (87%) of bTB-positive animals were asymptomatic, meaning infected animals could go undetected in the absence of routine surveillance and contribute to silent spread of infection. Almost half (46%) of bTB-positive bovines exhibited visible lesions on post-mortem inspection, and the carcase would be considered, in part or entirely, unfit for human consumption. However, due to the limited and sometimes conflicting evidence, the true burden in endemic herds and various settings remains poorly understood. The study highlights the paucity of the kind of detailed evidence that is essential for evaluating the benefit of any disease intervention and underscores the importance of considering the distribution of outcomes when supporting data are scarce.