What is bovine TB and how does it affect humans?

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Bovine Tuberculosis in Humans Explained

Singapore has recorded its first known case of bovine tuberculosis (TB) in a human, a 73-year-old former dairy farmer whose infection was linked to consuming unpasteurised cow's milk decades prior. This rare occurrence highlights the transmission routes of Mycobacterium bovis and the efficacy of public health measures like pasteurisation. While TB is endemic in Singapore, with over 1,000 new cases reported annually, bovine TB in humans remains an uncommon event in the region.
Understanding Bovine Tuberculosis

Bovine tuberculosis is an infectious disease caused by the bacterium Mycobacterium bovis. This bacterium is part of the Mycobacterium tuberculosis complex, a group of related bacteria responsible for tuberculosis in various species. Unlike the more common Mycobacterium tuberculosis, which primarily affects humans, M. bovis is predominantly found in cattle. The transmission to humans typically occurs through the consumption of unpasteurised milk and dairy products derived from infected animals. Globally, bovine TB remains a significant concern in livestock populations, with ongoing efforts to control its spread to prevent zoonotic transmission.
Transmission and Symptoms in Humans

The transmission of M. bovis to humans is most commonly associated with the ingestion of raw milk or dairy products from infected cattle. In the Singaporean case, the 73-year-old man's history as a dairy farmer until 1990, coupled with his regular consumption of raw milk during that period, strongly points to this route of infection. Symptoms in humans infected with bovine TB can be similar to those of pulmonary TB caused by M. tuberculosis, including poor appetite, weight loss, prolonged coughing, fever, and night sweats. The confirmed case in Singapore presented with pulmonary TB symptoms, and whole genome sequencing was instrumental in identifying the specific bacterial species.
Prevention Through Pasteurisation

Pasteurisation is a critical public health intervention that significantly reduces the risk of bovine TB transmission to humans. This process involves heating milk to a specific temperature for a set duration to kill harmful bacteria, including M. bovis. In Singapore, milk products are generally required to be pasteurised, a practice that has made human cases of bovine TB rare. The Communicable Diseases Agency confirmed that the identified case remains the only known human bovine TB infection in the country, underscoring the effectiveness of pasteurisation in preventing widespread transmission through the dairy supply chain.
General Tuberculosis Prevalence

Tuberculosis, in its various forms, remains an endemic disease globally and in Singapore. In 2023, the World Health Organization reported over 10.8 million active TB cases worldwide, resulting in approximately 1.25 million deaths. Singapore consistently reports a significant number of new TB cases each year, with 1,156 active TB cases among residents recorded in 2024, and 1,201 in 2023. While the majority of these cases are attributed to Mycobacterium tuberculosis, the detection of a bovine TB case highlights the importance of continued surveillance and public health measures to address all potential sources of infection.

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What is bovine TB and how does it affect humans?

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