Tuberculosis In Livestock

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Early in the century, there were so many infected cattle that many humans contracted TB from unpasteurized drinking milk.

If only one small lesion was found, that part was removed, and then the rest of the carcass had to be cooked in order to pass for human food (such as in the making of bologna).

During the 1930's, all herd of cattle in all states were tested, reactors removed, re-tested until clean, and then tested yearly. By 1950, few herds in the United States had cattle reacting to the test, and they were fast being cleaned up. Canada had been following a similar test and slaughter plan, and by the mid-1950s, tuberculosis was nearly eliminated. Tuberculosis-free cattle, pasteurization of milk, and better human hygiene nearly eliminated the disease in humans as well. However, other countries were years behind in eliminating tuberculosis in their cattle, and remained as a reservoir of the disease.

In the 1980s with cutbacks in money for the testing of cattle, importation of species that were not TB-tested (such as fallow deer and llamas), an increase in the size of untested herds of wild buffalo, and a general lack of knowledge and respect for the disease among livestock owners. Human TB also increased because of AIDS, the drug culture, homeless people, and a general breakdown in human hygiene.

How TB is Spread

Since tuberculosis first affects the lungs of most victims, whether human or animal, it is spread most often by saliva and nasal discharge, such as coughing. Common mangers, drinking tubs, and poorly ventilated stables can spread the disease to every animal in the barn if even one carrier animal is introduced to a herd.

In April of 1948, when I tested a barn of 80 mature dairy cattle, 63 reacted and were sent to slaughter. One cow, a carrier, had been introduced to the herd the previous November. Although the cow was fat and slick, and producing well, she was a generalized case of postmortem.

This barn was well ventilated, but had common mangers that were cleaned by sweeping. It is presumed that the sweeping carried the TB organism from the slobber of the infected cow to the rest of the herd. On a follow-up test, calves that were receiving milk from this herd reacted to the TB test. Despite the fact that some people drank raw milk from this herd, fortunately there were no human cases.

Remember that tuberculosis is spread by handling pets. Don't let animals lick your face, eat at the table with you, or eat from your dish.

Take Precautions

Although this is a veterinary column, I would be remiss in not mentioning how the disease is spread among humans. Although modern, human tuberculosis is primarily a disease of cities, even those of us lucky enough to live in rural areas have contact with people in public places.
Because of TB awareness from the early 1920s up until forty years ago, there were certain taboos: spitting in public, the use of common drinking vessels, and sharing food or drinking from the same glass, dish, or utensils. These are the main means of spreading TB. Saliva and nasal discharge from a human or animal infected with tuberculosis is loaded with tubercle bacilli.

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