Goals

[Airoh]

Hi Jean,
Can you tell us if there are any specific goals pertaining to the problem we have with TB in deer?
Short term?
Long term?
Are there any realistic thoughts of eliminating TB in N.E. Mi.?

[Fierkej]

The specific goals for the eradication of TB in free-ranging deer were established in 1997 by the State Committee on Bovine TB in Wild Deer. That committee advised that success will be measured by the prevalence rate with a goal to decrease the prevalence rate of Bovine TB in deer in the TB Core Area (old DMU 452) to less than 1 percent by the fall of 2003, and to have the disease eliminated in the wild deer herd by the fall of 2010.

Previous years and prevalence rates are listed below.

Year Apparent Prevalence in DMU 452 Hunt
1996 2.5 %
1997 4.4%
1998 2.6%
1999 2.3%
2000 2.5%

Some less formally stated working goals also include 1) preventing the disease from establishing itself as a self-sustaining reservoir in a species other than deer, 2) performing practical research to learn more about the dynamics of the disease in wildlife, and how to best tailor our management strategies to work towards eradication, 3) working cooperatively with the Michigan and U.S. Departments of Agriculture and Michigan State University to determine the best ways to minimize the risks of transmission from infected wildlife to livestock, and from infected livestock to wildlife and other livestock and 4) working with the Michigan Department of Community Health and the U.S. Centers for Disease Control and Prevention to better understand what the risks of transmission are for humans, and how to best minimize those risks".

Management strategies to reduce the transmission of bovine TB between animals are:
Ban feeding and baiting of deer and elk.
Reduce the population of deer.
Reduce the average age of the deer population.
Reduce face-to-face contacts between animals.
Ban new captive deer/elk enclosures.

The staff of the Rose Lake Lab is always available to answer other questions; call (517) 373-9358.

[Steve]

Is total elimination an acheivable goal?

[Whit1]

Originally posted by Fierkej
Management strategies to reduce the transmission of bovine TB between animals are:.......
Ban new captive deer/elk enclosures.

Bingo! Now there is an excellent idea. I also feel that a serious reduction in the present numbers of deer/elk enclosures is called for.

[Airoh]

They already did that a couple years ago in the TB zone Whit1.

[Whit1]

I'm not only talking about the TB zone. I'm talking the whole state. These captive herds have been the source disease, with CWD being the most outstanding example with untold, and dire consequences to our wild deer herd.

[Fierkej]

Hi,
I believe that Dan O'Brien already addressed this in his post under the Prevalence category (page 2)
I interpret "unable to sustain itself" to mean that it will disappear.
I also understand the goal is to "attain an undetectable level of infection" in deer.
Jean

Dan's discussion of herd immunity:

At it’s simplest level, herd immunity just means that in any population of animals, the variation in susceptibility of individual animals to infection means that a certain incidence or prevalence of disease is necessary in order for the disease to sustain itself. A threshold, in other words. Even though deer herds can obviously become infected and maintain TB infection on their own if conditions are right, in general, TB isn’t a self-sustaining disease in wild deer as it is in cattle. Isolated cases of TB in white-tailed deer in the U.S. have been written up since the 1930s, and there have been reports of TB in a variety of deer species in North America and worldwide. Other than here in Michigan, though, the disease has generally been unable to sustain itself in wild deer without having infected cattle around to keep it going. So, it’s pretty clear by now that deer in a wild setting have some degree of natural herd immunity, and that killing every single positive deer is, in all likelihood, not going to be necessary in order to break the chain of transmission that allows the TB outbreak to sustain itself in the Michigan herd.

However, just what the threshold of incidence or prevalence is that’s necessary to sustain TB in the herd isn’t known yet. Because we’re the first ones faced with this kind of self-sustaining outbreak, we don’t have the benefit of anyone else’s experience to go on. More importantly, no one should interpret what I’ve said here to mean that we don’t have to kill deer to get TB under control again. We do. The way we’ll likely figure out what the threshold is will be to continue to take steps we know will drive the probability of disease transmission down. That means reducing deer density, and reducing the situations that bring deer into close contact with infected deer and contaminated feedstuffs/areas. As prevalence of TB decreases, we should again reach the point where there’s insufficient transmission and susceptible animals for the disease to sustain itself. Once that point is reached, the risk for transmission to other animals and humans will be minimal.

Dr. Dan O'Brien
517-373-9358