DNR wants whitetail TB study to continue


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Nov 18, 2002
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DNR wants whitetail TB study to continue

By Linda Gallagher
Lansing — Although some problems were encountered during the first few months of a DNR’s whitetail collaring project in its battle to eradicate bovine tuberculosis from the state’s deer herd, researchers are hoping to continue with the new strategy this winter.
Instead of trying to reduce the prevalence rate of bovine TB in northern Michigan’s core TB zone by lowering the total number of deer, the new strategy attempts to locate specific animals with the disease.
Last January, in cooperation with Michigan State University, biologists began trying to pinpoint individual TB-infected animals by capturing deer in traps one at a time, taking blood samples, then radio-collaring each animal before releasing it back into the wild. The collars allow researchers to locate and kill the animal if test results indicate the existence of the disease. If not, the collars fall off in 90 days and can be retrieved for future use.
“That was the plan, anyway,” said Steve Schmitt, a state veterinarian at the DNR’s Rose Lake research facility. “But then we ran into some problems.”
Because of the time involved in shipping blood samples to be tested, the viability of critical white blood cells was already in question upon the arrival of the samples, and results from initial testing proved inconclusive.
“Results from the Cervigam test, which we had planned on using exclusively, were very good when used on deer infected with the disease in a lab setting,” Schmitt explained. “But it was a bit different when we began using the test on wild deer. A number of other variables were involved, and getting the samples in for testing while we still had live cells to work with was just one of them.”
Several other blood tests had to be conducted on the samples taken from the 119 deer captured and collared in northeastern lower Michigan. By the time results of that testing were complete, many of the collars on the deer, designed only to remain on the deer for three months, had begun falling off and were being recovered by technicians.
Although 31 of the captured deer proved suspect for TB, it was only possible to locate and kill six of them, according to Schmitt. “All of the other suspect deer had already lost their collars,” he said.
Only one of the six deer, a 9-year-old doe, was confirmed positive for TB.
“Considering the issues we had, we did pretty well overall,” Schmitt said. “We expected to have problems capturing the deer and getting the samples tested. We had initially hoped to catch and collar 200. And we’re very happy with the reception this study received from landowners in the testing area. We had excellent landowner cooperation, which was key to the success of the study.”
Schmitt believes the project, the first ever done on wild white-tailed deer, should be continued.
Currently, the rate of TB prevalence in Michigan’s free-ranging white-tailed deer is at an “equilibrium,” he pointed out. “The TB problem isn’t getting any worse, but testing has shown that it’s not getting a lot better, either. While the overall state disease prevalence rate is below 1 percent, in DMU 452, the core TB zone, the prevalence rate has remained steady between 2.3 and 2.6 percent. Some portions of the area are as high as 5 percent. In those areas, for every deer that’s harvested by a hunter or killed by a vehicle it appears that another animal contracts the disease.
“We need to do more to slow that rate of transmission down. This project may be the answer, if the funds are made available to us,” Schmitt said. “This could prove to be an additional weapon in our arsenal against bovine TB in our wild deer herd, in addition to ending the use of feeding or baiting in the core disease areas and our efforts to lower deer numbers with additional antlerless deer hunting licenses.”
Funding for the project was provided through a $2 million allotment from the state’s General Fund for bovine TB surveillance. A portion of that money, however, is being used to pay for the governor’s mandated domestic cervid CWD audit. Funding for next year has not yet been approved.

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