Beef testing continues

Laboratory tests continue to determine the source of the bovine tuberculosis that has infected five beef cattle herds in northwestern Minnesota.

Meanwhile, herds within 10 miles of the infected herds are being tested for bovine TB by veterinarians. Those costs are being paid for by the U.S. Department of Agriculture.

Detroit Lakes veterinarian Dr. Randy Lindemann, who joined the Minnesota Board of Animal Health staff last year, told a Bagley audience Wednesday that operators between 10 and 15 miles away should also consider testing their herds.

Lindemann was one of the featured speakers at the Beef Cow/Calf Days hosted by the University of Minnesota Extension Service. The annual event was held in several communities last week.

Lindemann said that since tests have found that a wild whitetail deer harvested near the first infected herd during the state firearms season had bovine TB, the testing has been expanded to bison and captive cerveids (deer, elk, etc.).

The Minnesota Department of Natural Resources took lymph node samples from 474 deer last fall. Since then, there are preliminary indications a second harvested deer may have bovine TB, but Lindemann said the results haven't been confirmed.

"It looks like it will be a positive deer," remarked Lindemann.

In the next several weeks, Lindemann said there will be several teams in northwestern Minnesota assisting in testing herds within the 10-mile radius of the five infected herds, which have been depopulated.

USDA dropped the state's TB-free status in late January and reclassified Minnesota as modified accredited advanced. That status places certain health requirements on cattle being shipped out of state.

The earliest the state can regain the TB-free status is Jan. 23, 2008, but Lindemann stressed "nobody says it won't be more than two years." If another Minnesota herd is deemed infected, the two-year clock is restarted.

Despite earlier suspicions the cattle may have contracted bovine TB from wild deer, Lindemann said DNA testing has determined the bacterial strain is similar to that found in infected cattle in the southwestern United States.

Lindemann said the owner of the first infected herd purchased cattle from a number of sources, which may be how the disease came to Minnesota. He said epidemiology tests are still underway to verify the original source.

Lindemann said it would be cost prohibitive ($8-10 million) to test the entire Minnesota beef herd, estimated at 800,000 head. The per-head cost is $10.

Bovine TB is a slow moving chronic disease that can't be detected by visual inspection. There isn't a vaccine to guard against the disease or cure it. When a human contracts TB, noted Lindemann, the individual must undergo repeated vaccinations for one year, costing hundreds of dollars.

Lindemann said the tuberculin test isn't 100 percent effective in detecting bovine TB's presence. He said there have been instances of live animals testing negative, but were found to have TB after being slaughtered.

The initial testing is done by a veterinarian, who injects tuberculin in the tail head area. Three days later, the injection site is visually inspected by that veterinarian. If there is a positive reaction, a second on-farm test is performed by a state or federal veterinarian. Another positive reaction could lead to the herd being quarantined and possibly depopulated.

Before that happens, the herd value is determined and then purchased by USDA. The animals are shipped directly to a slaughter plant.

Lindemann has been testing herds since December and has had only one suspect cow, which will be slaughtered to verify the on-farm test results.

Individual operators outside the 10-mile radius of infected herds can have their entire herd tested by veterinarian at their own expense in order to become a TB accredited herd. Some Minnesota operators have been doing those tests because they are selling bulls and heifers at upcoming production sales.

These operators must do an annual test to retain the accredited status, and follow MBAH guidelines when adding cattle to their herd.

Lindemann said operators who are holding production sales or regularly sell a lot of cattle may want to have their herds tested.

For persons buying at production sales, Lindemann said they should ask the sellers if the cattle have been tested before purchasing.