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Tuberculosis in Animals
Bovine tuberculosis is a strain of TB that infects cows and other animals, but it can also give people TB. The bacteria that cause bovine TB, called Mycobacterium bovis, are closely related to M. tuberculosis, the bacteria that usually cause TB in humans. Before the introduction of the pasteurization process of milk, bovine TB was a serious problem in Canada, and hundreds of children between the ages of 5 and 15 were affected and death from this cause was not uncommon. The boy pictured on the right got a TB skin infection by drinking bad milk (1923).
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A machine used for milk pasteurization in Canada in 1925. |
Heat pasteurization of milk, which means heating the milk to a certain temperature for a prescribed length of time, kills the TB bacteria found in the milk and makes it safe for humans to drink. Any milk that you buy in Canada today is safe to drink, thanks to this process. Another factor that helped prevent the spread of bovine TB in Canada was the elimination of infected herds of cattle, because cows are the source of the disease. When cattle become infected with TB, the bacteria infect the udders, and are carried in the milk. Humans that drink this infected milk ingest the deadly bacteria which produce TB. Bovine TB, when spread to people can cause crippling injuries to the bones and organs, and can lead to death if untreated.
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Deformities in the legs of a three year-old boy that contracted bovine TB from infected milk (1923). |
Before 1960, all cattle in Canada were tested for tuberculosis and infected animals were eliminated. The federal government gave farmers money to compensate for the cattle they lost, and today ensures that all milk sold in Canada is safe to drink by strictly enforcing pasteurization regulations. Bovine TB is no longer a major health concern in Canada, and you don't have to worry about drinking milk. However, if you are travelling outside of Canada, particularly to less-developed countries, it is important to check the packaging of any milk before you drink it, to be sure that it has been heat pasteurized.
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