Most mammals have the potential to become infected with M. bovis. Cattle, in particular, are susceptible to infection with M. bovis and may subsequently develop active tuberculous disease.
Humans usually acquire tuberculosis (TB) infection through the respiratory route, but historically in the UK consumption of M. bovis contaminated milk contributed to a lot of the notified TB cases. Although consumption of contaminated meat is a potential source of infection in the UK, it is considered a very low risk as the routine TB testing programme means that cattle with TB are generally identified at an early stage of infection and cases of advanced disease with TB lesions in the muscle and bone tissue are very rare. Animals testing positive on the screening test for TB are slaughtered and subject to detailed inspection.
Dr John Watson, head of respiratory diseases at Public Health England, said:
On the basis of the recent epidemiology of M. bovis infections in the human population in the UK, there is no evidence of a significant public health problem associated with the consumption of meat. The risk to humans remains very low.
In the past 10 years there have been fewer than 40 cases of human M. bovis disease notified in the UK each year. The majority of these cases have been in UK-born people aged 65 years and over, most likely due to reactivation of latent infection acquired many years ago before the introduction of control measures including routine pasteurisation of milk. The fact that we see so few cases of human M. bovis in UK-born children and young adults suggests that recent acquisition of infection in the UK is extremely rare.