After the discovery of five beef herds that tested positive for bovine tuberculosis (TB) in northwestern Minnesota, there has been a common concern among livestock producers and consumers of how this affects the safety of our food supply. While it has been quite awhile since beef producers in the upper Midwest have had to think about the impacts of bovine TB, there was a time when the disease was common. Prior to this year, the last known case of bovine TB in Minnesota was in 1971. So we do know some things about food safety that we should be concerned about, but also some things we do not need to be concerned about.

Bovine TB caused by the bacteria Mycobacterium bovis is a respiratory disease of cattle. It is a chronic, slowly progressive disease that does not spread easily. Infected animals may be capable of transmitting an infection to other animals even if they appear healthy. It is unlikely that the disease would be transferred from a live animal to a human. An animal would need to transfer respiratory secretions (sneezing or coughing and inhaling or nose-to-nose contact) to a human for this transfer to take place. Dr. Kevin Elfering of the Minnesota Department of Agriculture answered questions regarding food safety concerns from bovine TB. With the finding of a presumptive positive case of bovine TB in a white-tailed deer in northwestern Minnesota, other questions from deer hunters and venison consumers are answered.

Can I get tuberculosis from eating meat?
It is important to realize that with today's modern food production methods, the meat that you buy in the grocery store comes from animals that are inspected by meat inspectors and veterinarians for disease. These inspections take place both before and after the animal is slaughtered. This practice was implemented in the early 1900s primarily to remove animals with tuberculosis from the food supply. Animals with evidence of tuberculosis (enlarged lymph nodes) are removed from the food supply and tested for tuberculosis.

But what if a mistake is made and meat from an animal gets through into the grocery store?
This is pretty unlikely, but even if by some chance an animal did slip through, getting TB from meat would be unlikely because the bacteria that causes TB is found in they lymph nodes and not in the muscle (meat). Even when TB was common in cattle (the early 1900s) few cases of TB in humans were thought to be caused by eating meat from animals with TB. This is NOT the case with drinking unpasteurized milk. Additionally, adequate cooking (to 160 degrees F) kills the TB bacteria.

What about milk?
Milk purchased in the grocery store is free from TB because it is required by law to be pasteurized (heat treated to kill dangerous bacteria, including TB). The main reason for requiring pasteurization of milk was because of TB. The Centers for Disease Control and Prevention estimates that 20 to 40% of human TB cases in the 1900s resulted from drinking unpasteurized milk from cows with bovine TB. It is important to note that the recent cases of TB in Minnesota animal are in beef cattle, NOT in dairy animals.

What about unpasteurized milk?
Although the recent cases of TB in Minnesota animals have been found only in beef cattle and NOT in dairy cows, it is still unwise for people to consume unpasteurized milk for a number of reasons. Numerous illness outbreaks have been associated with drinking unpasteurized milk. Especially troubling is the potential for children and the elderly to get infected with Escherichia coli 0157:H7, by drinking unpasteurized milk. Although E. coli 0157:H7 does not cause any illness in adult dairy cows, infection with this bacteria can be fatal for children and the elderly. Other types of bacteria can also be unapparent in cattle but cause severe disease in humans (Camplyobacter and certain types of Salmonella).

How can I tell if a wild deer has bovine TB?
If a deer is exposed to bovine TB, it may take many years for symptoms to develop. The first sign is the formation of lesions on the lymph nodes in the head of positive deer. Most hunters wouldn't notice these lesions during normal field dressing. Lesions can progress to the lung and chest-cavity area. These are typically the first indication of disease that a hunter would notice. If there is question of disease, contact your local DNR officer for further evaluation. If the disease progresses further in live deer, you may notice emaciation, listlessness or respiratory disease symptoms but most cases do not progress this far.

I am a deer hunter, what precautions do I need to take?
It is recommended that hunters wear disposable rubber gloves while field dressing deer, which is a good idea regardless of the TB situation. Once an animal is dead, it can no longer expel respiratory secretions unless the lungs are cut open, which is the main route of transfer. In Michigan, where just over 500 wild, white-tailed deer have been tested positive for bovine TB, only one known hunter has acquired bovine TB. This hunter cut his hand while field dressing a TB positive deer. If you are concerned about having contracted bovine TB, ask you primary health-care provider for a tuberculosis skin test. The disease is treatable in humans with a 9 to 12 month regimen of antibiotics. As with beef, the bacteria is not found in venison and cooking the meat properly would kill the bacteria. However, if the animal is known to be diseased, it is not recommended to consume that animal.

The University of Minnesota Extension Beef Team, the Minnesota Board of Animal Health, the Minnesota Department of Agriculture and the Minnesota Department of Natural Resources are all committed to eradicating bovine tuberculosis from the state of Minnesota. Informational meetings will be held in January in northwestern Minnesota; watch for local advertisements and check the Beef Industry Center website for further details, www.extension.umn.edu/beef.