Mycobacterium Tuberculosis Complex

The Mycobacterium tuberculosis complex (MTBC) includes M. tuberculosis (the cause of most human tuberculosis), M. bovis, M. bovis bacillus Calmette-Guérin (BCG, the vaccine strain), M. africanum, and M. microti . M. bovis is the main cause of tuberculosis in cattle, deer, and other mammals. The human bacillus M. tuberculosis may have evolved from M. bovis in the setting of animal domestication. Human M. bovis infection generally occurs in the setting of consumption of infected cow's milk products.


Mycobacterium bovis, or the bovine tubercle bacillus, is an anaerobic bacterium that is part of the mycobacterium tuberculosis complex, and is the cause of TB in cattle. The organism is carried by many animals including deer, cats, dogs, pigs, alpacas, sheep and – of course – cattle. In a study of 4,715 mammal carcasses from the southwest of England, infection was confirmed in the following species: fox, stoat, polecat, common shrew, yellow-necked mouse, wood mouse, field vole, grey squirrel, roe deer, red deer, fallow, and muntjac deer.. Bovine TB can jump the species barrier and be a cause of TB in humans, and that’s where the problem historically lies.

In the UK today Mycobacterium bovis , no longer represent a real threat to the human population. Pasteurisation of milk has removed the bacteria. Cattle infected with bTB enter our food chain every day and we eat infected cattle. More than 22% of all new cases remain undetected until the animal is slaughtered. We often drink milk from bTB cattle. If only a few lesions are found, the meat is considered fit for human consumption. The government receives around £10 million a year by selling bTB contaminated meat into the human food chain.




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