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An animal health tale about us

Animal Health: News Roundup from the October 2018 issue of Canadian Cattlemen

October. The cattle come off the mountain pastures and the prairie grasslands into the corrals where the calves will be separated from their mothers. The lucky ones will stay on the farm or ranch as replacement breeding stock or be fed on the home place so the stress of weaning is minimal. Others will be trucked on contract direct to a feed yard where they will have to learn how to drink out of a waterer and feed out of a bunk. No more mother with warm milk and physical comfort but plenty of pacing, bawling and stress.

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Cow with Johne's disease.

But the worst affected are those which are bought at the auction by an order buyer for export. After the sale they must be processed, tested, tagged and held until the paperwork is completed, and sent for signature and returned before they can be loaded for the trip to the border and the final destination. The stress on these calves is substantial, many will become ill with pneumonia and some will die or suffer from chronic lung problems.

The latter group is our concern. It is time to call Wilbur in Helena, Montana, and determine the date after which the least amount of stress due to testing and processing will occur. The deep Texas drawl confirms that he has the same concern for the calves as we do and we agree to a date, consistent with the rules under the United States Department of Agriculture and the Canadian Health of Animals Branch, after which the calves can cross the border without testing for bluetongue or being held up for other reasons. The date is set and the cattle industry is informed.

At one of the United States Animal Health Association conferences I finally met Wilbur. Not a big man, smaller than his voice would suggest, but pure Texas from his Stetson past the silver belt buckle to his boots, clothes all whipcord and denim, black. Lean and tough, bone, sinew and tanned rawhide without an ounce of spare flesh was Wilbur.

But Wilbur had a history prior to being responsible for enforcement of the federal rules governing animal health in the State of Montana. He was involved in research, not cattle but sheep, and an enigmatic confusing disease which affected only adult sheep. Normal animals with no other sign of illness would begin rubbing against any solid object until the wool was worn off and eventually the hide would be scraped raw. The disease was first described in Scotland three and a half centuries before and was called “scrapie” by the sensible Scots. No one knew the cause of this condition and it affected only certain members of the flock, only in adulthood and there was no cure. It wasn’t caused by a bacterium and the science of virology was in its infancy. These tiny disease agents were separated into “filterable” and “non-filterable,” depending on their size, and if this was the cause, one was likely able to pass through a filter and was therefore unrecoverable and unseen.

The site of Wilbur’s trial involving infected sheep was at the northern end of the Wyoming Basin, an area important to the petroleum industry because the type of clay there when mixed with water was pumped down the drill stem to cool and lubricate the drill bit and flush out chips of rock for examination by the geologist to determine the presence of oil or gas. It was neutral, bland clay, unthreatening to living organisms. When Wilbur’s investigation revealed all it could, the data recorded and evaluated, the sheep were destroyed and the pens were cleaned out and left empty.

We go to Iceland next, a volcanic inhospitable island in the North Atlantic, that was first discovered by Celtic fishermen heading westward guided by their notched sticks to maintain a proper latitude, fleeing rampaging Vikings from what would become Norway. Here on that North Atlantic island, hot springs bubbled at the foot of glaciers, volcanic mountains stood on flat plains, short-season crops could be grown in some areas and a steady diet of fish brought on a hunger for mutton. So sheep were imported from home and raised in Iceland. But they developed scrapie and had to be destroyed. For a decade and a half no sheep were permitted on those particular premises until a new shipment of breeding stock, guaranteed to be scrapie free, were imported and housed on it. But in a short time they developed scrapie. This showed that the organism, whatever was causing the disease, persisted in that hostile environment for at least 14 years and possibly much longer.

Back in southern Montana at the research station where Wilbur had kept his sheep, a project involving elk captured from the wintering grounds of the wild herds on the eastern slopes of the Rocky Mountains was underway. At the conclusion of the trial the elk were not destroyed as were Wilbur’s sheep but these magnificent animals were returned to their herds in the foothills in apparent good health.

Meanwhile, people in Asia, particularly the Chinese, who were rapidly becoming wealthy and consumer oriented were demanding ever-increasing volumes of a health supplement derived from the growing antlers of deer termed “velvet.” Asiatic deer had spindly antler, New Zealand deer sported larger racks of antler but numbers were limited. North American elk had antlers which reached as far back as the bulls’ rumps when they walked through the forests. Antlers which in the velvet and full of blood and hormones weighed in excess of 40 pounds were worth a fortune when dried and processed. This opportunity could not be passed by so governments were pressured to allow the capture of wild elk to be raised in captivity for the collection and sale of the velvet to Asian customers. Permits to capture elk from the herds in the foothills were issued and some of the previous trial animals were likely captured as well as others and they became the basis of a new North American industry. Demand was great and elk were traded widely both interstate and internationally.

But all was not well. Occasionally, one of these magnificent animals would begin to lose condition, waste away and die. Then another would do the same. The symptoms suggested no commonly known disease but a search of the literature revealed that this condition had been reported in Scotland and was called “Chronic Wasting Disease.” Again, the sensible Scots had accurately described the disease in its name.

Not only the farmed elk were affected with this disease, which came to be known as CWD, but now wild elk and deer in the Wyoming basin as well were now affected. The cause was unknown, not all animals in a herd were affected, but those that were, died.

At about the same time, a disease of cattle was threatening both animal and human lives in Europe.This was a new disease which affected only adult cattle, they became unco-ordinated, nervous, then unable to rise and eventually died. It was named “Mad Cow Disease” or “Bovine Spongiform Encephalitis.” Frantic efforts to learn the cause and method of spread of this disease were underway and panic in other countries led to trade restrictions and the application of massive amounts of funding, much of it misapplied, to learn more about the condition. Transmission to humans was suggested and caused panic. Years went by and millions were spent and misspent before Dr. Stanley Prusiner learned that the cause of the disease was not a virus but was a normal element, a short string of nuclear material which, when folded normally was essential to carry copper ions across the cell wall into the cell where they were needed. The string was called a “prion” and in animals affected with BSE the string was misfolded into the mirror image of the normal prion and this was what caused the deadly disease in susceptible animals and humans.

Prion research proliferated and it became known that the BSE prion was biochemically identical to those which caused human spongiform encephalitis so the fear was justified. A prion was established as the cause of CWD and scrapie but the BSE prion was not identical to those which resulted in scrapie nor CWD, but the latter two were identical to one another. Only the BSE prion affected humans. Prusiner also showed that the prions were shed, depending on the species involved, in various body fluids such as urine and saliva, and in the flesh eaten by predators and humans. Stringent laws were put into place to stop the spread of these dreaded diseases and international trade in many commodities was restricted for years. But now the cause was known, the restrictions on feeding ruminant animal products to other ruminants were effective in preventing the disease and the number of cases worldwide decreased. It was shown that there was a genetic predilection or protection limiting the spread of those diseases in both animals and in humans but those without the proper genetic makeup when exposed to the misfolded prions faced certain death.

Unfortunately, the deer which were affected with CWD were not all captive deer; many had been part of the released study elk and now were feral, and in a few years the condition had spread widely across the North American continent, eventually reaching from the Rocky Mountain foothills to the Carolinas. It still appears sporadically in captive herds in Canada. The spread seemed to stop as it spread into the southern United States and has not been reported in the Florida Everglades.

A cartoonist at the time of the Viet Nam war, Walt Kelly, commented on the human condition and other social issues through the voice of “Pogo,” an opossum who lived under the Cypresses festooned with Spanish moss in the Florida Everglades along with all his little animal friends. One strip explained the foregoing tragedy extremely well, years before the actual events unfolded. In that strip, Pogo stood up in the prow of his pirogue with all his little swamp friends around him and he stated: “Gentlemen! We have found the enemy! And he is us!” How bloody true!

Larry Delver is a veterinarian and retired export veterinary program specialist with the Canadian Food Inspection Agency.

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