Q: Can cattle get TB from feed?
A: Yes, cattle as well as deer and other animals that eat feed on which saliva from infected animals has been deposited, and where the bacteria survives, can get infected. That has been shown in research in which infected animals were allowed to eat at feed and then were removed and that feed was fed to uninfected animals, all of which became infected. That is the scientific basis for eliminating the feeding and baiting of wild deer that can spread the disease within their herds.
In fact, survival of M. bovis on common deer bait feeds such as apples, carrots, corn, sugar beets and potatoes in an experimental study lasted at least 7 days on all materials and could still be isolated from apples, corn and beets at 112 days. It is believed that cattle grazing on pasture and eating apples from trees in pastures where deer have had access can be a means of transmission.
However, the question of whether harvested feed, such as hay, is a source of transmission has greater uncertainty. Experimentally, when dry hay was inoculated with M. bovis, survival in fall and winter was weeks or even months, however, survival in summer was less than 3 days. If saliva with bacteria is deposited on forage that is cut for hay or haylage, and cured in the sun for hours or days, there is lower likelihood of its survival. With haylage the process of ensiling results in the production of acids that preserve the feed. The impact of the ensiling process on the survival of M. bovis is under investigation in a 2013 study at Michigan State University. The hypothesis is that the bacteria cannot survive long and the intent is to characterize the death curve of the bacteria over time.
Q: What other animals on my farm could get bovine TB?
A: Horses and sheep are apparently resistant to TB and are not a concern. Goats and pigs can become infected. In addition, dogs and cats that drink milk from infected cows or eat tissues from infected cattle may also become infected.
Q: Can people get bovine TB?
A: Though the disease is called bovine Tuberculosis, people indeed may become infected with it, however, it is not a very high risk. Simply being around infected cattle and working with infected cattle has not resulted in human infections. The most likely way that humans would become infected is by drinking unpasteurized milk from a herd with infected cows. It was that means of transmission that provided the impetus years ago for laws requiring the pasteurization of milk for sale.