MSU Extension

All Michigan residents, in one way or another, have had to deal with the fact that bovine tuberculosis (TB) has been an on-going problem in Northeast Michigan for the past 20 years. The continued occurrence of infected farms has resulted in frustration and fear on the part of dairy and cattle producers who live under the threat of this disease. As a recent newscast in the area showed, it has also resulted in misunderstanding and fear on the part of consumers about the safety of milk and meat from farms in that region. Frankly, everyone is tired of TB.

In an earlier article from Michigan State University Extension it was discussed why buying out all the cattle herds in the TB zone is not a wise option, and yet, something has to be done. Every year since 2004, one-to-four additional herds have been found to be infected with TB.

So, what will it take to get rid of TB in Michigan? Typically, disease prevention for cattle herds is based on the six concepts listed below.

Straightforward ways that can be applied to TB risk mitigation/eradication:

Be committed to disease reduction.

It all starts with a commitment at the top to reduce disease prevalence, a commitment that is then communicated to others. On a farm, the owners must personally commit to disease reduction and then communicate this to each employee. At the state level, achieving the goals of TB eradication can only be realized if all involved parties support the objectives.

Know the source.

With other cow diseases, like mastitis, the first step is to determine whether the source of the pathogen is other cows (contagious pathogen) or the environment to which the cow is exposed (environmental pathogens). Once the source is known, efforts can be directed to target the source and reduce exposure. Likewise, we need to agree on the source of the bacteria that causes TB. We know for sure that deer can become infected with TB and are able to pass that infection to others. While many question the role of small animals (opossums, raccoons, etc.), it has never been shown that they can transmit the disease. Focus on what is known – deer can carry and spread the disease. Contact between livestock and deer through shared food sources is the means of transmission to be avoided.

Reduce the source.

When the source of an infection is known, the most important thing to do is to reduce that source. For example, if it is determined a cow has mastitis caused by the contagious bacteria Staph. aureus, often that animal is sent to slaughter to reduce the risk to the rest of the herd. If it were known which deer were infected with TB, then those animals could be selectively removed from the population. However, because infected deer can’t be determined, it is prudent to reduce overall deer numbers to the greatest extent possible in the TB zone. Other control options such as immunization of deer may be viable in the future, but until that is demonstrated, white-tailed deer population reduction is essential to TB control.

Reduce the conditions.

In this case there are two parts to be considered: reducing the conditions that enable the TB pathogen to survive outside of a host and reducing the conditions that allow the host to survive. The use of bait or feed for deer provides opportunities for the bacteria to survive and be transferred to another animal that eats at the same bait pile. All baiting and feeding has the potential to infect more deer with TB and other pathogens like chronic wasting disease, and should be stopped. In addition, steps need to be taken to reduce the environment on and around farms that may attract deer by providing habitat and food, making farms less hospitable for deer.

Reduce opportunities for exposure of cattle to the pathogen.

Clearly, there has not been enough done to reduce the risk of TB exposure. Here are recommended steps that herds use in combatting another disease: Bovine Leukemia Virus (BLV).

• Evaluate the entirety of the operation for disease risk. The risks to one farm may be different than those to another. Each one needs to be evaluated individually. Farm owners can improve in their ability to identify risks, able to understand and evaluate the potential risks his or her herd may face.

• Make changes in response to risk. Generally, there will be multiple risk areas with different levels of risk. Owners must determine cost-effective ways to reduce the greater risks, being willing to bear the cost because of the potential consequences of infection.

• Increase the level of management. In discussions with cattle owners about a disease like BLV, it is recommended that the changes made to protect animals from exposure need to be permanent because the risk is not expected to be eradicated in the foreseeable future. TB risk mitigation practices need to become the new standard of how things are done on the farm, even if that is different than how others may do so. Often, when changes are made to reduce the risk of one disease, there are risk reductions for other diseases as well.

Work together toward the same goal.

When trying to reduce disease it takes “all hands on deck”. To reduce TB, it will take dairy and beef cattle producers working together, it will take farmers and non-farm neighbors who manage property for wildlife habitat and hunting working together, and it will take agencies like USDA, MDARD, DNR and MSU Extension working together. Even with a difficult disease to control, like BLV, farmers can reduce its incidence in their herds, but it takes a lot of work, done consistently, and with everyone committed to it. This is also true for bovine TB.