<b>By TIM THORNBERRY<br>
Kentucky Correspondent</b> </p><p>

ST. PAUL, Minn. — Once considered to be eradicated, the Minnesota Board of Animal Health (MBAH) announced last week that a Roseau County beef cattle herd has tested positive for bovine tuberculosis (TB).<br>
The infected herd had been tested previously in 2005 and 2006 with no traces of the disease, but during a follow-up test last November, one animal tested suspect for bovine TB.<br>
After tissue samples were sent to the National Veterinary Services Laboratory in Ames, Iowa, the diagnosis was confirmed.<br>
This brings the total number of infected Minnesota beef herds to nine. The USDA is in the process of appraising the herd so it may be purchased and euthanized.<br>
Bovine TB resurfaced in Minnesota in 2005 after a 34-year absence, when the disease was detected in a harvested cow. That investigation led to the discovery of 21 more infected cows in that herd and an additional seven herds found to be infected, all in northwestern Minnesota.<br>
Since then, approximately 347,000 animals have been tested. The state’s Department of Natural Resources conducted TB examinations of hunter-harvested whitetail deer in the affected area. More than 3,000 deer have been tested in this region since 2005, with 13 testing positive and an additional four testing presumptive positive for the disease last fall.<br>
Bovine TB is caused by the bacteria Mycobacterium bovis and is a respiratory disease of cattle. Invisible droplets containing TB bacteria may be exhaled or coughed out by infected animals and then inhaled by other vulnerable animals or humans.<br>
Animals may also share the disease through common water supplies.<br>
Dr. Patty Scharko, extension veterinarian at the University of Kentucky Livestock Disease Diagnostic Center, feels the outbreak is likely isolated but that caution should be observed, especially with animals going into or out of Minnesota.<br>
“I feel like this is isolated in an area up there, and I know the officials there are doing everything they can to keep it that way,” she said. “The likely hood of such a disease making it to the food chain is all but impossible, with the extensive examination of beef at the time of slaughter. Federal veterinarians have a handle on this.”<br>
Primary screening for bovine TB is usually performed through the caudal-fold tuberculin (CFT) or tail test, which can only be done by a USDA-accredited veterinarian. The test is read by the same veterinarian in about 72 hours. If any signs or abnormalities, such as discoloration or swelling, are found at the injection site, the animal is classified as a CFT test responder, the herd is quarantined and the animal must be retested by a state or regulatory veterinarian using the more definitive comparative cervical tuberculin (CCT) test.<br>
Scharko warns that testing is critical.<br>
“The testing has to be done properly. The tail test is easy to do, but there will be some false positives with this test,” she said.
A Web report by Michigan State University extension noted: “A response to the CFT test indicates that the animal has mounted an immune response capable of recognizing Mycobacterium bovis. Although the response may be caused by infection with Mycobacterium bovis, exposure to or infection with other closely related bacteria, such as Mycobacterium avium (avian TB) and Mycobacterium paratuberculosis (Johne’s disease), could also cause a CFT test response.<br>
“This is referred to as a false positive test. It is expected that false positive results on the CFT test will occur in a normal population approximately five percent of the time.”<br>
According to the USDA’s Animal and Plant Health Inspection Service (APHIS), the disease was once “the most prevalent infectious disease of cattle and swine in the United States,” causing more “losses among U.S. farm animals in the early part of this century than all other infectious diseases combined.”<br>
However, the creation in 1917 of the Cooperative State–Federal Tuberculosis Eradication Program, administered by APHIS along with state animal health agencies and U.S. livestock producers, has nearly eradicated bovine TB in this country, which has also led to a decline in the number of cases reported in humans.<br>
Because the disease can be transmitted to the human population, the most effective way of handling the problem of bovine TB in humans is to eradicate it in livestock according to the APHIS.