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Published May 11, 2008, 12:00 AM

LivesTalk column: Eradicating bovine TB in MN?is critical

One of the most important agricultural issues in Minnesota right now is the eradication of bovine tuberculosis

By: Dr. Bill Hartmann, MN State Veterinarian, DL-Online

One of the most important agricultural issues in Minnesota right now is the eradication of bovine tuberculosis (TB). And for the Board of Animal Health, bovine TB is our most important issue. We remain committed to eliminating this disease from Minnesota cattle and returning our state to TB-free status.

Minnesota’s TB-status has been downgraded to Modified Accredited (MA) — the third level of a five-tier scale — and this has changed, yet again, the way Minnesota cattle producers do business. We know that this situation has been difficult for cattle producers.

To help people understand what this means and how it might affect their business, the Board, along with our state and federal partners and the University of Minnesota Extension, has held numerous public meetings throughout the state. If you were unable to attend one of the meetings, I will answer below some of the common questions we heard around the state.

-- How can my herd become an accredited TB free herd? Producers must first apply to the Board of Animal Health to initiate the accreditation process. Second, a whole herd TB test must be completed and at that time, the herd must begin to comply with all of the rules for herd additions under Accredited Herd Status.

To qualify for Accredited Herd Status, the herd must complete a second whole-herd TB test within 9 to 15 months of the first test with no evidence of bovine TB. Once approved for Accredited Herd Status, owners must test all cattle in the herd, 12 months of age or older, every year to maintain accreditation.

-- What is the process for obtaining split state status? Who makes the decisions? The Board is developing a plan for split state status that considers factors such as the locations of TB-infected cattle herds and deer, TB surveillance in cattle and deer throughout the state, statewide distribution of cattle herds, deer density in the affected area, and common cattle marketing practices in Minnesota.

A split state zone will be established and rules for herd management and animal movement will be implemented so as to prevent the spread of TB out of the zone. USDA has final authority to recognize Minnesota’s plan after we have proved that the infection is effectively contained.

-- Why do TB-positive herds have to depopulate? Could infected cattle be removed from the herd? Prior to the establishment in the early 1900s of the national bovine TB eradication program, five percent of the cattle in the U.S. were infected with the disease. At that time, it was considered sufficient for the purpose of eradication to simply remove infected cattle from herds.

However, TB is now present at such a low prevalence that there is very little margin for error. The only guaranteed method of eradication is to depopulate the entire infected herd.

Depopulation allows the cattle producer to return more quickly to regular production. An infected herd would have to remain under quarantine for a minimum of 4 1/2 years and need at least eight whole-herd TB tests. While under quarantine, a producer would likely find the cattle to be unmarketable except directly to slaughter and even after the 4 1/2 year quarantine, some herds have still been found to harbor the disease.

-- What do positive farms have to do to repopulate?

Based on USDA regulations, after a TB-positive farm has been depopulated, the premises must be cleaned and disinfected. After a 30-day period, the producer can then bring cattle back on to the farm, but will have to TB test the herd annually for two years following repopulation to ensure that the disease is not present.

-- Have we figured out where the TB came from?

After an exhaustive investigation, we have not been able to determine the origin of the disease. The strain of bovine TB found in northwest Minnesota, is similar to a strain found in the southwestern U.S. and Mexico but is not an exact match.

When investigating an infected herd, we identify animals that were added to the infected herd and TB-test their herd of origin. We also identify animals that were purchased from the infected herd and test their current herd. Hundreds of animals were traced within Minnesota, and to a nine other states, and we have not identified a source of the TB infection. Because the disease develops slowly, it is possible that it was present in the region for some time before it was discovered.

More information

An extensive list of questions and answers can be found on the State of Minnesota Bovine TB Response Website at www.mntbfree.com — click on “Frequently Asked Questions.” As always, if you have questions or concerns, call us toll free at 1-877-MN TB FREE (668-2373).

Dr. Bill Hartmann is the state veterinarian with the Minnesota Board of Animal Health.

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