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Hoping for a status upgrade

After about 16 months of an intensive statewide testing campaign, Minnesota cattle producers suffered a setback when word of a new case of bovine tuberculosis was reported Jan. 22. The new case, the second since Oct. 1, means producers are at ris...

After about 16 months of an intensive statewide testing campaign, Minnesota cattle producers suffered a setback when word of a new case of bovine tuberculosis was reported Jan. 22. The new case, the second since Oct. 1, means producers are at risk of having their USDA bovine TB status further downgraded.

The Statewide Bovine TB Surveillance campaign was begun in September 2006 as part of a comprehensive plan by the Minnesota Board of Animal Health in concert with USDA to identify and eradicate bovine TB from the state's livestock populations and regain Minnesota's TB-free status. USDA requirements called for testing all animals 18 months or older, but according Linda Glaser, senior veterinarian for the cattle programs division at Minnesota's Board of Animal Health, testing of all cattle 12 months and older, including a variety of at-risk populations in and around Roseau County, designated as the "core area," was required by BAH.

BAH and USDA performed three different testing plans for each of the three specific population categories, she says. The first was testing every cow at the original cattle operation in Roseau County. The second required extensive testing within a 10-mile radius of that ranch, as well as checking all herds through which TB-positive animals from those ranches may have passed. The third was statewide testing of 1,550 other herds.

"It is unnerving," Glaser says of the latest case, but says the majority of testing now is completed. Only a certain amount of "trickle testing" between now and Sept. 30 remains.

An agreement between USDA and BAH requires that, if three TB-positive animals are detected between Oct. 1, 2007, and Sept. 30, 2008, the state BAH leadership will be required to discuss with USDA whether the TB status should be further downgraded to "Modified Accredited," the middle of five levels. If a fourth detection occurs before Sept. 30, this downgrade is mandatory.

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Restrictions under MA status are stricter.

"We would have to address TB in deer, including statewide testing," Glaser says.

The state board also would have to report twice as often to USDA, describing the current status of the herds, what measures are being taken to address TB in them and what the effects of these measures are.

Most importantly, though, incidence of TB-positive animals would have to decrease.

"We would have to prove less than 0.01 percent occurrence within the herds," Glaser says, noting this to be the equivalent of one herd in 10,000.

On the other hand, for the Minnesota herds to be upgraded from Modified Accredited Advanced back to Accredited Free status, they must be proven free of bovine TB for a period of two years after the destruction of the last herd in which an animal was proven TB-positive, Glaser says.

Combating bovine TB

Texas, New Mexico and Michigan had been the only states to suffer outbreaks in the last decade until February 2005, when a 5-year-old beef cow was identified by USDA meat inspectors as a bovine TB suspect, USDA reports state. The animal, detected at a Green Bay, Wis., facility, was traced to a 600-head ranch in Minnesota's Roseau County.

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USDA and BAH placed the herd under quarantine while more tests were performed. An additional 21 "suspect" animals were detected. Tissue samples were sent to the National Veterinary Service Laboratory in Ames, Iowa, for complete analysis, which on July 12 confirmed the diagnosis of bovine TB in nearly all of these animals, according to BAH reports.

It was the first TB-positive herd identified in Minnesota since the state's herds were declared free of the disease in 1971. It is not clear where the disease originated, according to BAH documents. The herd was destroyed, and an examination of herd records led to protective quarantine of 14 other northwest Minnesota herds and locator traces to Iowa, Kansas, Nebraska and South Dakota.

Volunteered herdWhen Van Swanson of Thief River Falls, Minn., heard about the planned testing in early September 2006, he volunteered his cattle.

"When (BAH and USDA) initially had their meeting, they said they were going to be testing 1,500 herds in the five or six surrounding counties," he says.

Swanson was sure his cattle would have to be tested, so he volunteered. By doing so, he figured he could at least get them tested before spring calving.

He and his veterinarian began in the last week of September. Swanson's two neighbors dropped in to help set up holding pens and round up the cattle, and the veterinarian brought the chute.

TB testing requires two separate contacts with each animal, according to USDA. First, each is given a small shot under the tail. Each animal will then be rechecked three days later to determine if there has been a physical reaction, in the form of swelling, around the shot site. If there is, then a second test must be performed by a state veterinarian.

It took about six hours to set up and run the cattle through Swanson's chutes that first day, he says. But when the veterinarian returned to check the sites, one of Swanson's cows tested positive.

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"We had to sort out that one and catch her again," he says. "I put her in a separate pen, and then from the time they found this swelling, she had to have a shot from the state vet. She got two shots up in the neck area."

It would take another three days of waiting before they would come back and check the new sites. If his cow tested positive again, his whole herd would have had to be destroyed, he says.

"You're hoping it is that false positive, but in the meantime, you're thinking, 'What's happening?'" he says. "But they told us that 7 percent to 8 percent of the cattle tested showed a false positive."

His cow's first test results proved to be just that, a false positive, and his herd was deemed by the state veterinarian as free of bovine TB, he says. It cost him and his neighbors roughly 12 hours of effort apiece as well as some measure of concern.

This scenario was being duplicated around the state as BAH and USDA scoured Minnesota cattle for signs of the disease.

The testing campaign ended Jan. 2. In all, about 1,850 herds were tested, uncovering eight other herds with bovine TB, all in Roseau County and neighboring Beltrami County, Minn., to the south, Glaser says.

Recognizing that the producers of the 1,550 tested herds from outside the core area faced a complicated and time-consuming task, she says, "These individuals went above and beyond for their industry and we thank them for that."

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