A statement released Friday by the North Dakota Department of Agriculture said that no sign of bovine tuberculosis has been found in the first round of testing of a herd of cattle from the southwestern part of the state. A second round of testing is now under way.
The investigation began in October 2008 when, in the span of one week, four positive tests for TB were found after slaughter. Three of the positive tests were linked back to herds in Minnesota while the fourth was linked to a herd in the southwest part of the state. That positive result came after a TB lesion was found after slaughter at a processing plant in Long Prairie, Minn.
Every member of that herd, numbered at roughly 200, was skin tested in December. The result of that initial test revealed 28 "suspect" cows, resulting in the need for additional testing. Those "suspect" cows were slaughtered so that tissue samples could be analyzed at the National Veterinary Services Laboratory in Ames, Iowa. All 28 of those samples came back negative for TB in early March.
"The information we have from the processing plant indicates that we definitely have the right herd and we also requested DNA testing to confirm that we have the right animal," said Beth Carlson, deputy state veterinarian.
The herd in question has been quarantined since October, meaning that the herd can't come into contact with any other animals and no member may be sold.
By law, the testing process is being repeated, starting with the skin testing of the entire herd. That test resulted in one "suspect" cow which was recently slaughtered and is now being tested with results expected in the next eight to 10 weeks.
If the second round of testing also comes back negative, the quarantine imposed on the herd will be lifted, but if the second round results in a positive test, the entire herd will be destroyed.
"We are cautiously optimistic that the second test will be negative," Carlson said.
In addition to that herd, four neighboring herds are also being tested as part of standard procedure. Carlson said two of those herds have already been tested, both with negative results, a third is in the process of being tested and the fourth will be tested after the conclusion of the calving season later this spring.
Bovine tuberculosis is an infectious respiratory disease that is spread through oral or nasal secretion. The disease poses a threat to wildlife because it can be transmitted to white-tailed deer, elk and bison, although there has never been a documented case of that occurring in the state. The cost to destroy any infected herds or wildlife can cost hundreds of thousands of dollars depending on how many animals are affected and how widespread the problem is.
North Dakota has been designated TB-free since 1976 even though a dairy herd in Morton County tested positive in 1999 it was destroyed because federal guidelines allow a state to keep its designation if it has only one TB case in any two-year time span. Even if the second round of testing is positive, North Dakota will be able to keep its TB-free status unless another case is found within the next two years.