# Prevalence



## Huntnut (Jan 21, 2000)

Hello Jean!
Welcome to our site, you are greatly needed here, and I appreciate the time and effort you will undoubtedly contribute! 
I have followed our TB issue as close as I could the past few years.
I have spent my life wandering the Michigan woods. There is no place on the planet that I feel more at home. I majored in wildlife biology and bio chemistry at the University of Alaska Fairbanks, and contributed to some of the arctic ground squirrel studies that school is so famous for. I also got the chance to play in some muskox and caribou research while there.
I returned to Michigan in 97, and enlisted as a hunter/manager in our BovineTB "war".
After discussing issues with fellow hunters, a question arose that has yet been sufficiently answered by my research. I am hoping you can shed some light on the issue of disease prevalence.

For arguements sake,(and easy #'s), let's say the core area holds a population of 100,000 deer. Lets also say that 1 out of every 1000 deer in the core area is tb positive. In this scenario, we have a 0.1% TB prevalence rate within the population.
The DNR ,in turn, issues unlimited doe permits for the core area, and greatly encourages hunters to harvest as many deer as possible.
After a few years of unlimited permits, the herd is greatly reduced by 75%, leaving 25,000 deer in the core area.

Now here is my question, how do we know that the hunters will harvest an equal ratio of positive to nonpositive animals?

In the scenario above, the pefect ratio would be 75 out of the 75,000 harvested deer are tb positive, leaving the 0.1% prevalence rate.
The successful ratio would be something like 90 positive tb deer out of 75,000 harvested, thus lowering the prevalence rate.
The losing ratio would be something like 50 positive deer out of 75,000 deer thus increasing the prevalence rate. 

Put simply, if hunters harvested all the deer in 452 except for 100, and even 1 individual has BovineTB, the prevalence rate within the population has now jumped to 1%. In theory, a 1% disease prevalence rate would consume the total herd much faster than the current 0.1% prevalence rate.

Either way, there is no possibility of eliminating every tb positive animal to reach our 0% prevalence tb free status.

Am I wrong?

It seems to me, the only way to eliminate Bovine TB from Michigan is to eliminate all animals that are capable of contracting Bovine TB, and keep our TB area free of animals until the disease is no longer viable in the environment.

We aren't doing that though, and it seems that all we are trying to do is lower deer numbers, not prevalence rate. What is the difference if we have 100,000 deer with a 0.1% prevalence rate or a million deer with a 0.1% prevalence rate? It is the prevalence rate we need to attack, not the population level.

The closest explanation, that I have read, is the DNR is trying to lower deer numbers in an attempt to lower deer interaction to slow the spread of transmission. I have a hard time believing that we can lower deer interaction for 2 reasons:
1. The rut...at this time of year, the only thing in a deer's head is to get together with other deer.
2. Migration and winter yarding areas. The deer in the northern part of the state herd up in winter yarding areas, and share the same browse as the rest of the local herd to get through winter.

There is no way to eliminate deer interaction, no matter how many individuals comprise the total herd. Unless there are no individuals to interact. 

There was one individual on this site that suggested letting the 452 herd expand way beyond carrying capacity. End hunting, and begin massive supplemental feeding. 
Then let one winter without supplemental feeding choose which animals are healthiest.
I hate to say it, but it seems that this method would eliminate far more TB positive animals than any other strategy, and lower the prevalence rate much further than an army of hunters harvesting indiscriminately would. 

I am greatly interested in knowing the flaws in the above trains of thought.

Huntnut


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## Fierkej (Dec 21, 2001)

FYI..... 

Due to the holiday many DNR personel are out of the office unit January 2nd. The site will be monitored, although some issues on the forum may not be addressed until after this date. 

Happy Holidays! 

Julie


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## Guest (Dec 29, 2001)

Huntnut,
I agree with you so far on this issue.I like some of your points that you made.I doubt the DNR will take you seriously.They cant handle the truth!


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## Fierkej (Dec 21, 2001)

Hi,
Arent we all in search of truth in understanding why tuberculosis is in the deer and other wildlife, when it normally is not found in wild deer living in wild conditions? Scientists from the world over are trying to determine which theories are actually the truth regarding tuberculosis. 
Which of the following contributes most to the maintenance of the disease in wild deer?
· Contact with a deer that is capable of transmitting the disease? We are fairly sure that a deer that can spread the disease to other deer needs to have open draining abscesses connected to the repiratory tract, so that it can cough out contagious pus. These abscesses could be in the lungs, throat, or back of the mouth. 
· Contact through the mammary gland? The mammary gland must have draining abscesses.
· Contact with urine from an infected deer? 
· Ingestion of feed at feed piles, bait piles, and near farms that has contagious pus on it? Does it take more than one exposure to become infected?
· Breathing in air near feed that has contagious pus on it?
· Brushing by or eating from a plant that has contagious pus on it?
· The deers immune system can fight off introductions to the bacteria. If the immune system is not up to par, at what level does it loose the fight against the bacteria?
· If a deer is infected but not contagious, what must happen for the condition to become contagious?
· How many times does a deer need to be exposed to a source of bacteria to become infected?
· Is interaction with other deer the most important source of exposure to contagious material? 
· Does the age and sex of the deer make it more likely to become infected? 
· What is the threshold level of exposures to contagious material and aerosol below which the bacteria wont do well in a population of wild deer?
· How big a role does the weather play in the maintaining the bacteria in an environment? 
Ive listed these just to illustrate the intricacies of eradicating TB in wild deer. Many of these have been studied and/or are being studied. All have some effect on the prevalence of the disease. Most of the research is listed on www.bovineTB.com under The Disease section. The truth in how to eradicated tuberculosis in deer will slowly be elucidated. Again, the bacteria has evolved over the past 1,000s of years to do well in livestock situations. It did not evolve with wild deer living in wild conditions.
Jean


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## Joe Archer (Mar 29, 2000)

Huntnut, excellent post. I have been on the prevalence page with you from day one, and was the person who suggested an alternate way to use mother nature to reduce prevalence.

Fierkej, I appreciate your response. The only problem I have is why did we have to jump the gun on the TB eradication plan? We know it has been in the wild for over 20 years. Couldnt we have spend a few years doing research to specifically answer some of the questions that you offered? As it stands right now, the plan is a crap shoot designed to reduce herd numbers. If we increase the prevalence this rate will be maintained when the herd is allowed to recover, and we will have done more harm than good.

I was in favor of gathering information and putting together a plan based on evidence, and not a plan based on theory. <----<<<


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## Huntnut (Jan 21, 2000)

Hello Joe!
Admittedly, you were the one that put the prevalence issue in my head, and believe it or not, you changed my mind way back then 
You also brought up the alternative method. My original post above should have been yours! Ever since we had that discussion, you have had the gears spinning in my head about prevalence.

Jean,
I understand that there is alot we don't understand about Bovine TB. The questions you posed above should be answered.

Couple questions,
Are we using penned control groups to find these answers? Or are we using the entire North Eastern herd as our control group?

"The truth in how to eradicate tuberculosis in deer will slowly be elucidated. "
If we don't know the truth yet in how to eradicate tb, why are we promoting the slaughter of deer in the North Eastern Lower?
It seems we are acting on an unknown premise.

We all want to see TB disappear. We want to see it disappear in the cattle, the deer, the carnivores, the raccoons, the cats, etc...
But our current plan entails only killing the population of one of many hosts.
If a TB positive coyote can cough pus and pass it to cows, why aren't we also attacking coyote's? Or raccoons, or cows, or elk?
Why only deer?
I see that there have been 38 cases of TB found that were not found in deer. Who knows how many non deer TB cases have not been found.
Even if we do succeed in removing 99% of the deer in 452, the remaining 1% could still contract the disease from the coughed puss of another animal. 
I am not bashing you folks at all, I greatly appreciate the fact you guys are trying to squash a disease. But it seems you are only focused on deer when there are many other hosts.

My greatest fear is that TB will spread all over the state in the future. If that happens, our sport will be dead along with the hunting economy.

Jean, you are right, TB has never been found in a wild deer herd until now. We don't know why, but one things for certain...the deer in 452 live in the same proximity to cattle and agriculture as every deer in this state. How long till the powers that be decide we need to erradicate all of the deer in this state? Do you think we will know more about this disease before they decide to do this?

Hunt


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## Airoh (Jan 19, 2000)

Hopefully Jean will give us an opinion on your ideas for lowering the prevalence rate.

I would like to take a stab at your first post. 
The idea of no hunting and winter feeding a few years will worsen a condition that already existed in the core area. Overpopulation and poor stewardship practices could very well be the root cause for sustaining the bacteria in that area. 
If we did what you suggest I think the stress you would put on that herd will bring the overall health of that herd lower than it already is. When you do this then try to starve the sick you will kill many TB positive deer, but because of the stressful conditions you will have transferred the disease to a larger number of the herd because of the overall lower health of the herd. Many of these deer will not die off over the winter which will maintain or create a higher prevalence rate. Another minus would be that you will kill off a very large portion of that years fawns. This will alter the age structure of the herd. The herd will be older, and an older herd is a less healthy herd.

Huntnut.You said  Put simply, if hunters harvested all the deer in 452 except for 100, and even 1 individual has BovineTB, the prevalence rate within the population has now jumped to 1%. In theory, a 1% disease prevalence rate would consume the total herd much faster than the current 0.1% prevalence rate.

I disagree with that theory also. If you carry that scenario out to the point of only two deer left leaving a 50% infection rate, this would be a much better scenario for eliminating TB from the herd because of the almost impossibility of the two deer ever coming in contact with each other. The point being that if you create large parcels of land with no deer you are more likely to eliminate interactions of deer carrying the bacteria.

I'm not saying the current attack on TB is the best course of action, I just do not think trying to winter kill an over populated herd will work lower the prevalence rate.

I am glad to see hunters such as yourself showing a genuine concern for the health of our herd. Thanks for your input.


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## Fierkej (Dec 21, 2001)

Hi,
Your comments about overpopulation/starvation lowering the prevalence of TB sound good. 
I will see if Dr. Dan O'Brien has time to comment on this thread. 
Jean


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## Huntnut (Jan 21, 2000)

Airoh,
You may be excatly correct in your deductions. 
The DNR may be right in theirs.
I may be right in mine. 
I really don't know the truth....and this post is an effort to help educate myself on the truth of TB.

Point is, nobody seems to know, and that is what worries me.

Thankyou for your interpretation.

Hunt


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## Fierkej (Dec 21, 2001)

Response from : Graham Hickling
Visiting Research Scientist from New Zealand
MI DNR Wildlife Disease Bureau


1) The urgent goal of the DNR/DMA TB eradication strategy is to prevent Tb spread from deer to cattle. The number of new cattle infections per unit time is likely to be primarily related to the number of tuberculous deer in the surrounding forests. So if the overall deer population were lowered by, say, 50% we should get a 50% reduction in the abundance of tuberculous deer and thus a 50% reduction in the incidence of new cattle cases. 

2) The longer-term goal is to work towards eradication of the disease in both deer and cattle. Let me give you a hypothetical example of the way we think that deer population reduction help achieve this:

Population reduction helps break the disease transmission cycle, because loss of Tb from the deer population occurs through the death of infected individuals, and the death rate is only weakly influenced by deer abundance. In contrast, the gain in new Tb cases IS strongly dependent on population numbers, because it is essentially the product of [No. infectious deer] x [No. susceptible deer] * a transmission coefficient.

For example, if there are 50 infectious deer in an area, let's assume that about 25 will die during the coming year regardless of whether they are part of a dense or sparce population. And let's say that the 50 Tb deer are mixed in with 1000 healthy ones, and that prior to control the loss of the 25 Tb deer that died each year was being exactly balanced by 25 new infections; i.e., TB prevalence was staying constant over time. 

This set of assumptions implies a transmission coefficient of 0.0005 (because 50 x 1000 x 0.0005 = 25 new cases each year).

If that population were then reduced by 50% by heavy hunting, there would be 25 Tb deer left immediately after the hunt. A year later, about 12 of these would have died. And over that same year, there would have been only 6 new Tb deer cases (I get the 6 by calculating that the 25 Tb deer were exposed to 50% of the original 1000 healthy deer x the 0.0005 transmission coefficient).

So .... a year after the operation the number of Tb deer in the population will have dropped from 50 to 19 (which makes the cattle happy).

And the prevalence of Tb in the deer will have dropped from 4.7% (50 in 1050 prior to the hunt) to only 3.6% (19 in 525), which makes the DNR and the hunters happy. 

If the population was held low for, say, a decade, Tb prevalence would gradually decline to very low levels.

Obviously there are numerous complexities that aren't included in this example (e.g., young deer have a longer life expectancy than old ones, high densities may push more deer into contact with cattle, etc etc), but it does illustrate the general principle that current management is based on.


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## Joe Archer (Mar 29, 2000)

Hi Graham,

The only problem I have with this theory is the assumption that equal numbers of deer will die pre and post intervention. In many areas (my area for example) the deer numbers have been reduced so far below the carying capacity of the land that winter kill is no longer a factor. 

If you want to muddy the waters a bit more you probably can suggest that the intervention (drastic reduction in deer numbers) is selective for younger animals. If the probability of contracting TB is any way related to age, and we are selectively increasing the age of our herd, we may be increasing the odds that any single animal be positive for the disease. 

If our goal is to prevent the spread of disease to cattle, I can see the effectiveness of the current plan. If our goal is to maintain a huntable resource for future generations, again, I am worried that we have missed the boat. <----<<<


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## Graham (Jan 5, 2002)

Fair comment, Joe.

My key point is that TB prevalence has not be changing much in recent years (I'll be putting out a new report on this shortly) which means that inputs (new TB cases) and outputs (deaths of infected deer, for whatever reason) have been roughly in balance.

So management actions that helps to reduce the input side of the equation (by lowering the number of infectious animals, or susceptible animals, or transmission) should help to lower overall TB prevalence, although it may take some years for the effect to become evident.

Regards, Graham


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## Huntnut (Jan 21, 2000)

Graham,
I used to hunt 452 once every year...until some locals bashed me pretty hard for shooting does.
I felt pretty bad, and decided that the resident deer hunters of that area will make their own decisions for their area.
I haven't been back since.

It seems there is great animosity between the local hunters methods and the TB erradication methods.

I hear local hunters say don't shoot does 10 times more than I hear you folks say to shoot them.

I want to know what is actively being done to promote antlerless harvest over and above the liberal doe permits.

Also,
Can you estimate the yearly value of the cattle industry vs. the deer hunting industry in our states TB area?

Hunt


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## David G Duncan (Mar 26, 2000)

Excellent discussion thread!

Since my training is in the area of Electrical Engineering and not animal health I am reluctant to offer any comments. But I have spent a lot of time in the woods and on the farm. So here goes nothing.

First, my thinking is closely aligned with the points made by Airoh.

My current viewpoint is derived from the fact that in 1994 or there abouts my brother-in-law, who is also an avid hunter, lived within the city limits of Tawas. The deer population in Tawas was so out of control that they had deer in their backyard almost every night. He also, told me about driving into the surrounding country side near farms and seeing upwards of 150 deer in an evening. They were mostly undersized and not that healthy looking.

It seems to me that this was a very unnatural condition and could very likely have triggered some kind of health problem in the local deer population. Therefore, it seems logical that reducing the deer population density should be a logical approach to improve the health of the deer herd.

I also fear that this reversal process could take much longer than the time required to cause the problem in the first place (probably 10 years) and the population might need to be lowered significantly below normal low levels in the recent past.


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## Graham (Jan 5, 2002)

Good morning Hunt,

You asked: 'can you estimate the yearly value of the cattle industry vs. the deer hunting industry in our states TB area?'

I'm not sure that's quite the right question, because the TB issue is costing farmers throughout the State, not just in the TB area. 

What I can tell you is that as a consequence of the resurgence of TB in livestock, Michigan lost its bovine TB 'accredited-free' status in June 2000 and is now designated as modified accredited. One analysis done by APHIS in 2000 calculated that this loss of status will have a cost of between $22 and $74 million if it continues for a 5-year period.

I'm probably not the best person to comment on the deer $$$.

Regards, G.


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## Fierkej (Dec 21, 2001)

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Dan OBrien, D.V.M., Ph.D.
Rose Lake Wildlife Disease Lab, MDNR
8562 E. Stoll Rd.
East Lansing, MI 48823-9454
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>










Hello All,

Jean asked me to take a look at this long thread and offer some comments. Essentially all of the issues that have been raised in it so far have come up before (numerous times, actually) in letters, e-mails and the many meetings weve had with various groups all over the state for the past several years. But apparently we havent done a very good job of getting our points across in those forums, since people still obviously have a lot of questions.

Anyway, here are some points that will hopefully be helpful in the discussion. I throw them out here on a one-time basis, meaning I probably wont have time to answer any additional questions they might bring up on the list. However, Jean is very capable of answering most of what might come up, and anyone with specific unanswered questions is always welcome to call me at Rose Lake (517:373-9358) and Id be glad to discuss these issues with them.

--------------------------------------------------------------

&#61623; On prevalence as a tool for measuring disease: So were all on the same page, prevalence is just the number of existing cases of disease divided by some reference population. Its a measure of the existing reservoir of disease at a particular point in time. More specifically, as we commonly use it with respect to TB, its apparent prevalence, that is, the number of animals that test positive for TB divided by the number we test in a given time period. Like any percentage measure, prevalence is vulnerable to manipulation. As you decrease the reference population, any change in the number of disease cases has a much greater impact on the prevalence. That may or may not have an equal impact on the actual transmission of the disease. To use an example already raised in this thread, compare a theoretical scenario where there are 100 positive deer in a population of 100,000 (0.1% prevalence) in an area of 600 square miles, to an alternative where there is 1 positive deer in a population of 100 (1% prevalence) in the same 600 square mile area. In the second scenario, even though the prevalence is 10 times higher than the first, the risk of disease transmission is dramatically lower, because the likelihood of an uninfected deer having close contact with an infected individual is much lower. Thats because theres 99 fewer positive animals running around in that area. So, looking at prevalence all by itself can sometimes be confusing. Both the number of positive animals and the prevalence are important, and effective control strategies ultimately have to deal with both.

There are a variety of different ways to measure disease occurrence, all with their own strengths and limitations. Id encourage anyone whos interested in further reading on this to look at references 1-4, listed at the end of this posting.

&#61623; On how do we know that hunters will harvest an equal ratio of positive to negative animals?: Strictly speaking, we dont. However, in the case of TB there is essentially no reason to suspect that there is an appreciable bias in harvest toward either positives or negatives. First off, tuberculosis only very rarely affects the deers nervous system. That means that there is no reason to suspect (and no data of which Im aware that shows) that having TB affects a deers behavior in a way that might make it more (or less) likely to be harvested. Second, only in its most advanced stages does TB produce symptoms in deer that might allow a hunter to tell that the animal was sick. Those cases only occur in a small percentage of the positives. Third, even when that happens, the symptoms those animals show are not specific to TB (weight loss, respiratory symptoms), so even if a hunter saw a skinny lunger deer and shot it, its much more likely that hed be killing an animal with some disease other than TB. Fourth, probability dictates that as the harvested population gets larger, random fluctuations that might bias the sample one way or another have less and less effect.

&#61623; On the possibility/need to eliminate every TB positive deer in order to effectively eliminate TB from Michigan: Given the technology currently available, its unlikely we could identify all the positive deer in the state and kill them all, even if that was our goal (which, by the way, it isnt). But its absolutely critical to understand that that will likely not be necessary in order to a) eliminate the ability of TB outbreak to sustain itself in the deer population, b) reduce to near zero the likelihood of transmission to cattle and c) reduce to near zero the risk of transmission to humans. A key concept thats in play in this situation is called herd immunity (see reference 1, p. 540; and reference 3, pp.91-94). 

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.

&#61623; On the idea that lowering deer interaction is impossible: Two points I want to make here:

1) Eliminate and reduce are two entirely different things. There is no question that, short of killing all the deer (which we cant, and dont want to, do), contacts between deer that could potentially transmit TB cannot be eliminated. However, they dont need to be eliminated in order to reduce them substantially, and so greatly reduce the opportunity for disease transmission. Just because we cant eliminate all contacts between deer is not an excuse for throwing up our hands and doing nothing. Eliminating all contacts will likely not be necessary to cut transmission of TB back to the point where it cant sustain itself in the herd (see discussion of herd immunity, above).
2) Think of contacts that are opportunities for transmission of TB as being of two different types: natural (that is, part of the natural history and behavior of deer) and man-made (that is, things that humans do that aggregate deer that arent part of their normal behavior in the wild). In the big picture of disease transmission, these two types of transmission opportunities are cumulative. While the impact we can have reducing natural contacts is limited, we can, and should, drastically reduce the man-made contacts between deer caused by activities like feeding and baiting. Man-made contacts greatly add to the opportunities for TB transmission over and above the natural ones that already exist. Also consider that many of the natural contacts provide opportunity for transmission for only a fraction of the year (rut, yarding, etc.) while some man-made contacts (feeding) occur year round.

&#61623; On massive supplemental feeding, followed by withdrawal, as a strategy for TB control: Someone in this thread (Airoh) has already made some excellent points on this issue, and is on strong scientific ground with his/her comments. Id only add the following. 

1) The surveillance data that weve accumulated from testing deer for TB since 1995 suggest that older deer are more likely than younger ones to be TB positive (not surprising, really), and that bucks are at higher risk of being positive than does of the same age. That risk increases with age. In a scenario where supplemental feeding is encouraged and then withdrawn, dominant animals will be better able to compete for existing food sources (see reference 5) and much more likely to survive the withdrawal. In general, that will be older animals, and in particular, older bucks, the same animals that are most likely to be infected.
2) Supplemental feeding would (and does) promote spread of the disease to other species. Species that normally would have minimal close contact with deer (for example, elk) are attracted by the food source, and so are much more likely to contract TB that they would be otherwise. In addition to contact, food contaminated with TB bacteria from the respiratory fluids and saliva of infected deer acts as a source of infection for other species that eat that food later. This is most likely the way that the elk herd has been infected with TB. Tuberculosis bacteria survive quite nicely on common feedstuffs used for supplemental feeding, even in freezing weather. 

&#61623; On the idea that were only focused on deer when there are many other hosts for the disease: The important thing to keep in mind here is that theres a huge difference between being capable of being infected (a host) and being a source of infection for other animals (a reservoir). Our TB surveillance activities involve testing of a variety of species other than deer. Over a thousand elk have been tested since 1996. Over twelve hundred carnivores/omnivores of fourteen different species have been tested during the same period. Twenty seven furbearers have cultured positive so far. Cultures on another three are still pending, but in all likelihood, those will eventually be positive as well. In all but a handful of cases, those animals had no visible signs of tuberculosis in their bodies at all. The only way we detected them as positive was because carnivore tissues all get cultured as a matter of routine. So, even though these species are capable of being infected, they (at least so far) do not develop the progressive disease with large amounts of bacteria that are likely to be shed outside their bodies and infect other animals (see reference 6). That makes them hosts, but not reservoirs.

Thats completely different from the situation we see in the deer. Not only has our surveillance work documented that wild deer develop extensive signs of disease when theyre infected with TB (reference 7), but we also know that they can and do spread the infection to each other (reference 8), and to cattle, not only by direct contact, but indirectly through contaminated feed. That makes them a reservoir, a source of infection for other species. Thats why the emphasis is on the deer. It isnt that we arent concerned about other species, its simply that other species are not the problem at this point. Until we effectively deal with the TB situation in the deer herd first, we wont get wildlife TB under control in this state. Period. Whats worse, unless we do deal effectively with TB in the deer, we risk having the disease become established in other species we know are capable of being reservoirs, like the elk. If we as citizens of this state allow that to happen, we should all truly be ashamed.

&#61623; On the idea that we should have waited to start eradication efforts until more was known about the specifics of the TB situation in Michigan: When diseases infect populations, they dont wait around while people decide what should be done. They keep multiplying, spreading to other animals as quickly as conditions allow. Thats how they survive. The fact that TB was likely present in the deer herd for forty years before it was recognized as the outbreak it was isnt a good justification for waiting even longer before we attempt to bring it under control. If anything, it makes the situation much more urgent. Outbreaks of any infectious disease are nearly always much easier to get rid of when theyre caught early.

The whole point of epidemiology as its used in the field is to try to step in and work towards control of a disease outbreak even in situations where everything about the situation isnt known with certainty. Even though there are things we still dont know about the specifics of TB in Michigan, theres a heck of a lot we do know already about tuberculosis as a disease. Its been around in cattle (and people) for thousands of years, and more is probably known about TB than any other infectious disease. We know enough about transmission of TB to know general measures (reducing animal densities, reducing man-made contacts between deer) that are highly likely to be effective in reducing prevalence of TB. While those efforts are underway, it gives us the chance to do research (which we are), to learn about the more subtle aspects of TB in Michigan wildlife. In effect, these general control measures not only move us in the right direction towards broad control, they buy us some time while we narrow our focus to target more specific things.

It wouldnt be an exaggeration to say that history is littered with examples of situations where a great deal of disease could have been avoided if people had had the will to act aggressively at the early stages of disease outbreaks. In my view, if we dont take TB seriously and act aggressively to control it, right now, we will all pay the price down the line. So will the wildlife we all say we value so much. So will our heritage as hunters. And, so will our children when we pass on to them a wildlife resource we were supposed to be stewards of, a resource affected by a disease we could (and should) have controlled.

I hope that these comments are of some use to folks on this list. Whether you agree with them or not, I hope they will encourage at least some of you to seek out more scientific information on TB, and that they will provoke useful discussion. Again, feel free to call me at Rose Lake (517:373-9358) if you have specific questions. Jean will field all follow-up posts to the list, and any e-mails. Thanks for your patience in reading this long post.

Regards,
Dan


References/further reading

1. Rothman, K.J., Greenland, S., 1998. Measures of disease frequency. In: Modern Epidemiology, 2nd Edition. Lippincott-Raven, Philadelphia, pp. 29-46.

2. Thrushfield, M., 1986. Describing disease occurrence. In: Veterinary Epidemiology, 2nd Edition. Blackwell Science, Ltd., Oxford, pp. 37-59.

3. Martin, S.W., Meek, A.H., Willeberg, P., 1987. Measurement of disease frequency and production. In: Veterinary Epidemiology: Principles and Methods. Iowa State University Press, Ames, pp. 48-78.

4. Hennekens, C.H., Buring, J.E., 1987. Measures of disease frequency and association. In: Epidemiology in Medicine. Little, Brown and Co., Boston, pp. 54-98.

5. Williamson, S.J., 2000. Feeding wildlifeJust say no. An explanation of why feeding deer, elk, wild turkey and other big game is more often curse than favor. Wildlife Management Institute, Washington D.C., 34 pp.

6. Bruning-Fann, C.S., Schmitt, S.M., Fitzgerald, S.D., et al., 2001. Bovine tuberculosis in free-ranging carnivores from Michigan. J. Wildl. Dis. 37(1):58-64.

7. OBrien, D.J., Fitzgerald, S.D., Lyon, T.J., et al., 2001. Tuberculous lesions in free-ranging white-tailed deer in Michigan. J. Wildl. Dis. 37(3):608-613.

8. Palmer, M.V., Whipple, D.L., Waters, R., 2001. Experimental deer-to-deer transmission of Mycobacterium bovis. Am. J. Vet. Res. 62(5):692-696.


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## marty (Jan 17, 2000)

I would like to know if other states test their deer for TB and if not why? It seems that if TB is so bad other states would want to know if this was in their deer herd too.

I also read where Texas has been working on new vaccines. Has Michigan research this to see if this would work on cattle?

Another thing I don't understand is why farmers leave round bales out in their fields? This seems like a great breeding ground for TB to exist. I been told that this is the Dept of AG corner but if TB could live in these conditions why wouldn't something be done about it ?

Thanks for your time.......marty


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## Airoh (Jan 19, 2000)

Thanks for responding. I feel the more info hunters have on a subject the better they will be able to help. Any info from the DNR's bioligists, scientists, and vets will be appreciated. This site may be one of the better places in the state for sharing information with concerned sportsmen.


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## DaYoop (Oct 26, 2000)

Marty,

the current problem with vaccination is testing. The vacc works really well but you cant tell the difference between Vaccinated animals and Diseased animals when testing, and that creates a big problem with a zero tolerance to diseased animals.

As far as other states not testing--if you don't know its there you can basically say you don't have it, and with all the problems Michigan is facing with TB, why would any other state admit they have the disease as well. It is my opinion that other states have it as well, but just aren't looking to find it. Kind of shooting yourself in the foot if you ask me.


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## marty (Jan 17, 2000)

Exactly my point yoop. It seems if TB is so bad as the experts say it is other states would be checking their deer also......marty


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## Tom Morang (Aug 14, 2001)

I took this from the Wisconsin DNR site, it says they are looking for TB in it's herd. Jean may know of more states...........tm



Are Wisconsin wild deer infected with TB?

We do not believe our wild deer are TB infected. Surveillance of Wisconsin
deer for TB has been done since 1996, with more than 1500 deer tested and no
positive animals found. WDNR will continue annual testing to monitor for TB. As a
hunter, you may be asked by DNR personnel to provide a small tissue sample from
the head of your deer. This is voluntary, but your cooperation is important in
detecting this disease.


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## DaYoop (Oct 26, 2000)

Thanks Tom, I'm glad to see that. It only makes sense to begin testing. 

I admit I'm guilty of speaking without looking--I did not search to see if other states were testing, I just have not heard of it (see my point that if you don't look for it you won't find it)

Can you provide the site you found that on for me? I would like to see what their methods are, # tested compared to # shot.

Thanks Tom,

DaYoop


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## Tom Morang (Aug 14, 2001)

Your welcome. Click on the link and it will take you to the WDNR web search site. You can type in Bovine TB in the search box and go from there. This subject came up before that's why I remember that Wisconsin did some checking for TB in it's deer herd. 

Let us know if you find anything interesting.


http://www.dnr.state.wi.us/WWWSearch.html



tm


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## DaYoop (Oct 26, 2000)

started new thread.....


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## sargent (Oct 1, 2001)

Marty,

You and I have brought up the same points of farming practices and yet these concerns seem to be ignored.

A friend of mine tells me about a disabled farmer (now theres an oxymoron ) who hunts deer with his x-bow out at the corn crib and then feeds that same corn to his cattle!

Farmers can leave hay and harvesting byproducts in their fields (how many times have you seen farmers put cattle into freshly harvested corn fields to clean them up? Deer frequent these fields too! Or how about the feed wagons with fresh chopped hay and silage left in the fields for cows to eat at will, Deer frequent these areas as well.

Farming is too big of an industry and these practices will never change. Its much easier to target the deer and attempt to wipe them out which will never happen. Unless EVERYONE is willing to change their practices Tb will continue even with the deer herd reduction.
The Michigan Farm Bureau wants our Deer population wiped out and Tb seems to be a perfect cover for them to push for it.
I have cancelled my Farm Bureau auto insurance because of the Farm Bureaus positions concerning deer management.

My .02


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## Fierkej (Dec 21, 2001)

Response per Bridget Patrick, Communications Coordiantor, Bovine TB Eradication Project:

Both MDA and the Department of Natural Resources (DNR) have a reporting procedure in place whereby landowners are contacted and provided with information and warnings regarding the feeding of deer in the 12 northern Michigan counties where baiting and feeding is banned.

The MDA telephone number with the Division of Environmental Stewardship is: 517-241-0236

The DNR telephone number with the Division of Law Enforcement is: 1-800-292-7800.


Per Bridget Patrick,
Communications Coordinator
Bovine TB Eradication Project


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## boehr (Jan 31, 2000)

Fierkej...are you sure of the number for the DNR? That's the Report All Poaching number and I doubt if the dispatchers in the communications room are going to be able to give much if anything about TB, except maybe another phone number.


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