cwd forum - II
I didn't take a head count, but there must have been 50 of us at the forum for chronic wasting disease (CWD) in Central City. Which was apparently quite impressive to the three highest bosses of the outfit, since the meeting was voluntary. 'Course, a lot of it was a social gathering, having folks from all across the state. The lead veterinary fellow couldn't get the room quiet enough to start. Even when they flashed the lights on and off, conversations held on at a dull roar.
Finally, one of the number two bosses got up and shouted "Hey!", and we were able to start.
As our vet began, he asked who had heard his CWD powerpoint talk before. Fully half the room raised their hands.
"Well, you'll have to suffer through it again."
"Suffered the last time," was a response from the back.
So, what's new with CWD?
Back in the 60s and 70s, when folks first realized this was something infectious in deer, most work centered on trying to find a virus as the cause. The idea of a deformed protein, a prion, being the cause was a major new insight.
Well, pure forms of prions have been extracted now. And guess what you get when you inject animals with the pure prion?
No disease. Yup, no CWD, or BSE, whichever you're dealing with. Inject extracts from infected brains, though, and you get the disease. So they figure there's got to be something else involved as well, something that activates or introduces the prion.
Like a virus.
So, some research is going back to the ideas of the 60s and 70s.
In describing the sponge-like ("spongiform") nature of brains of infected animals, the vet mentioned "Holes in the brain are not good, not conducive to long life."
No chit, Dick Tracy.
Incubation in deer is still 600-800 days, but when visible symptoms show up, death is usually only a couple weeks behind.
Game farms are still the main suspects in moving the disease to a lot of states and provinces, like Wisconsin. In southern Wisconsin, in response to their local infection around a game farm, the state basically declared war on deer, trying to eradicate animals for miles around the infected area using their people and hunters.
Didn't work. It's in wild deer in northern Illinois, now.
Our neighboring state to the south tried a similar approach, reducing deer and elk numbers by 25 percent in a couple areas along our border. Their infection rates crept up, slowly, while ours nearly doubled in the same time period. So, basically, we can slow the spread, but not stop it.
The lone, isolated case in White Sands, New Mexico has company now. Nine confirmed. The discovery of this isolated pocket ("focus") of CWD far from any other sources was considered by some to be an indication the defective proteins could arise naturally. The term used was "Immaculate Infection." But as they investigated, rumors have popped up from several different sources that some years back, the military commander of White Sands was disappointed in the low deer numbers on his base and had some brought down, serruptitiously and illegally, from Colorado.
And presumably brought the CWD with them.
To date, there are still no cases of humans contracting CWD, from eating infected deer or by any other means. But the professionals, being the scientists they are, will never say it could "never" happen. As was pointed out, "it's hard to find volunteers for such a study. You can only fool graduate students for so long."
The prevailing belief now is that the disease (and BSE, or mad cow disease) came from scrapie in sheep, and somehow jumped the species barrier, presumably by cattle and tame deer being fed feeds that included infected sheep parts.
And it is pointed out that scrapie has been in sheep in North America for over 50 years, and Europe for over 150 years, and still no people have caught that, either. Despite the fact that people have "eaten, sheared, and done all sorts of unnatural things to sheep over all those years."
Amidst all the snickering over the "unnatural things to sheep" statement, a voice from the back threw back, "Speak for yourself."
Regarding the other spongiform encephalopathy in the news, mad cow disease (BSE), estimates are that close to 250 million people were exposed in Europe. To date, only 140 people have contracted the disease. So, basically, we were a lot more likely to get hit by lightning or have a car wreck on the way home from the meeting than exposed Europeans were of getting BSE.
Far as I know, we all got home safe.
So far all 140 cases in Europe had the same genetic marker they mentioned to us two years ago, suggesting most people are genetically immune to BSE.
Another big concern is whether or not CWD could jump to cattle. We're now six years into the study where 10 cows are housed with infected deer and elk. So far, all cattle are fat, squared off and happy. Presumably they think they're in bovine heaven, as all they do is eat and sleep, and never worry about the butcher. Expectations are that they will finally die of cardiac arrest from being fat and lazy. But no sign of spongiform disease.
Likewise for the 20 cattle that had extracts of infected deer brains injected into their brains. All doing fine and well after six years.
Bad news is, a single moose that was experimentally injected came down with symptoms (but died of something else, because moose are notoriously hard to keep alive in captivity. To quote the vet, "Moose die just to spite you.). Another moose calf ("mooselet" the vet called it) is now living with infected deer to see what happens.
Antelope still appear to be immune. Presumably their brain proteins are too different to deform like deer's. They tried injecting a bunch of antelope fawns with infected brain extract, but coyotes broke into their pen and killed them all, so that research has to begin again.
Other bad news learned in the past two years: elk calves and deer fawns can be infected as early as six months of age. Which wasn't a surprise, but has been confirmed, now.
The prion that causes scrapie has been found in low density in sheep muscle tissue (meat), not just in the brain and spinal cord. Which is both bad news, and good. It suggests that eventually we may find the CWD prion in muscle, too, which may be bad for publicity. But it also means Europeans have been eating the scrapie prion for over 150 years, and still no one gets sick from it. Which is good.
We now know the infectious agent, whatever it truly is, remains viable in the environment for at least three years. And that it comes out in the feces of infected deer (via the lymph glands that line the intestines, which got into details more graphic than the questioner wanted), and infects any deer or elk that eats same. And remains after their carcass is naught but bones.
Unlike antelope and humans, so far it appears no deer or elk have any immunity to CWD.
Last fall we collected 6,125 samples for CWD testing. Of these, only 115 were unusable, which the lab folks considered remarkable. More remarkable was that more than half of these 115 came from just one sampler, who had managed to collect over 60 thyroid glands, rather than lymph nodes. Which the vets tell us are much harder to find and extract than lymph nodes. But, despite much cajoling, they declined to identify the talented, but ignorant, cutthroat.
Of the 6,025 usable samples, only 177 tested positive for CWD. Most of these in the endemic areas, where we already knew the disease existed. Almost 20 percent of the samples from one area came up positive.
Lab guy went through the entire processing process, explaining with justifiable pride how they have sped up and streamlined the time from collection to results to less than three weeks. And then complained that they spent another two and a half months trying to figure out locations for these samples from the hunter descriptions on the data forms.
Some of their conclusions:
- An awful lot of hunters had no clue where they were.
- Our state has way too many Smith ranches.
- Our ranches tend to be big, many over 40 sections, so knowing the ranch name does nothing to pinpoint a sample location.
- People have too many nicknames for places.
- We have too many common or large features, like Sand Creek, Muddy Creek, etc.
Despite all that, we found CWD in 10 new hunt areas last year. None of mine, yet, but I'm surrounded on three sides. It's only a matter of time.
In closing, we were advised CWD sampling will be tapered back this year, to mainly the areas next to the endemic areas.
And they will be holding training sessions again, near the end of summer, "in case you can't remember the difference between lymph nodes and testicles, like Ron."
Ron being one of the height-challenged mouths in the back of the room.
"But his are so close together," came his defense from another corner of the room.
So, anyway, we're all being asked to save and freeze heads of roadkilled deer to practice on until then.
"If your wife doesn't mind."
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