FOOD FOR THOUGHT: Mad Cow and Wasting Disease

Have you been reading the papers, watching the national news or listening to talk radio? If so, chances are you've been exposed to the term Mad Cow Disease. First in Great Britain, then in Canada, and most recently a cow in Washington State, the scare – if not the actual disease – has spread. Recently, even a case in Goats has been confirmed in France!

We know it is possible for a variant of Mad Cow Disease to be passed to humans through meat consumption. What about our pets? Are they also in danger?

Whether feeding a premium brand kibble, or hypoallergenic proteins of venison or elk, dog owners are curious:

Let's take a look at Mad Cow Disease and what the experts have to say.

What Is Mad Cow Disease?

Bovine Spongiform Encephalopathy (BSE), or Mad Cow Disease, is a transmissible, slowly progressive, degenerative disease having an extremely long incubation period – – some experts quote three to nine years. The disease affects the central nervous system of cattle causing symptoms such as excessive salivation, staggering gait and weight loss. The animal usually dies within six months of becoming symptomatic.

The long incubation period means that there is a very long period where an animal is infected but does not appear ill.

BSE is caused by an abnormal version of a protein called a prion, which is scientific shorthand for proteinaceous infectious particle. The BSE found in cattle can be passed to humans through contaminated meat and has been named Variant Creutzfeld-Jakob Disease (vCJD).

BSE is part of a larger group of disease referred to as Transmissible Spongiform Encephalopathies (TSE). TSEs are neurological diseases pathologists have characterized by the tiny holes they inflict in brain tissue. When viewed under a microscope, they make the brain look like a sponge.

Currently, the nature of the transmission agent in is not understood. Several theories exist and the one most accepted is that the responsible agent is a modified form of a cell surface component known as a "prion protein."

Heating, boiling, cooking, freezing, ionizing, radiating, autoclaving, sterilizing, bleaching, or even using formaldehyde cannot kill prions. Scary, huh?

The most effective way to stop the spread of prion diseases, per the USDA and FDA, is through early identification and removal of any diseased cattle from the human food chain.

Let's first look at beef intended for our consumption, and how prion disease has affected it's processing, and then we'll focus on beef and those beef byproducts that are ingredients in our pets' foods.

Human Consumption of Beef Products

Mad Cow Disease was first implicated as causing vCJD in humans in the mid-1980s in Great Britain. The mode of transmission appears to be that infected animals were processed as cattle feed and then fed to other cattle that were then consumed by people. The BSE prion mutated and appeared in humans as vCJD.

There are limited portions of the steer carcass thought to carry the offending prion. They are the brain, spinal cord, and other nervous system tissues. These are referred to as specified risk materials (SRMs) by the FDA, USDA and meat packers.
BSE infectivity in cattle tissue is:

Brain 64.1%
Spinal Cord 25.6%
All other tissue <1.0%

Muscle meats, experts state, should be safe for human consumption, even if they are from an infected steer. That said, no meat products from countries shown as having BSE or being at risk for it are permitted for importation into the American market.

While the USDA tells us that muscle tissue is safe, killing methods in slaughterhouses and the possible contamination of brain and central nervous tissue into other tissues during mechanical meat recovery make the countries of the European Union (EU) uneasy. Therefore, the EU banned all mechanically recovered meats (MRM) for human or domestic animal feed.

In the United States (U.S.), this ban on MRMs is scheduled for implementation only in products intended for human consumption, starting in July 2004, reported MSNBC on July 10, 2004. Excerpts follow:

"As of July 10, 2004, six months after the first reported case of Mad Cow Disease was found within the U. S., the FDA banned the use of some high-risk meat in foods and cosmetics. The new rule only mirrors a regulation put in place by the Department of Agriculture in January 2004 banning the use of "specified risk materials" in human food, dietary supplements and cosmetics, as well as the use of cattle that cannot walk and mechanically separated beef.

The Consumer Federation of America was extremely disappointed that the FDA did not take action on rules and regulations proposed back in January 2004 but instead called for "further comment." This prompted Jean Halloran, Director of the Consumer Policy Institute to say: "They are actually spinning their wheels backwards."

Milk and milk products, even from BSE infected cows, or from the 31+ countries now identified as having BSE or being at risk, are allowed into the U.S., as dairy products have not been shown, in laboratories, to cause TSE infections in the same or in other test animals.

Safety Measures and Concerns

The bottom line from government agencies is that striated muscle meats such as steaks, roasts and ground beef, together with fat, bone and milk are not infective, because they are not believed to contain [enough of] the BSE-causing prions and therefore are assumed safe for people, even if the source cattle were found to be infected.

Since the discovery of infected cows first in Great Britain, then in Canada, and now one (or possibly more) within the U. S., the USDA has announced implementation of some new safeguards. These safeguards fall far short of those called for by consumer groups and scientists. (See below.)

This new rule was very interesting to me, as a pet owner: "Meat from downer animals will no longer be allowed into our human food supply. These animals are called 4D for dead, dying, diseased and disabled. "

However, 4D animals can still be used in commercial pet foods and feed for poultry and swine.

Restrictions have also been placed on slaughter and processing methods to "increase the likelihood" tissue from the nervous system of the cow does not end up in meat products. I don't know about you, but I'd personally prefer the phrase "positively prevent."

New and better methods of tracking cattle have also been proposed and debated. Final determinations on tracking and record keeping requirements, like many other suggestions, are still "pending" before various groups and committees within the USDA.

Restrictions have also been placed on slaughter and processing methods to "increase the likelihood" tissue from the nervous system of the cow does not end up in meat products. I don't know about you, but I'd personally prefer the phrase "positively prevent."

New and better methods of tracking cattle have also been proposed and debated. Final determinations on tracking and record keeping requirements, like many other suggestions, are still "pending" before various groups and committees within the USDA.

Is Your Dog at Risk from Eating Kibble, Hooves or Rawhide?

In a word, the general consensus of the international scientific community is a resounding "NO." For reasons unknown, dogs appear to be immune to prion diseases. Cats, however, are not so lucky.

Many animal experts recommend that any dog food containing beef or beef byproducts be kept away from felines, even though there is no reason to believe that BSE is present in American dog foods.

The FDA states: "There is no evidence to date that dogs can contract BSE or any similar disease and there is further no evidence that dogs can transmit the disease to humans. With the exception of cats, no pets are known to be able to contract Mad Cow Disease."

Scientists at Medi-Cal Pet Foods state: "In contrast to cats in the UK and France, there has been no disease reported in either cats or dogs in North America. The absence of BSE-type diseases in dogs is interesting and may indicate a genetic resistance or species-barrier to this disease in dogs."

In May 2004, The Canadian Food Inspection Agency (CFIA) learned 1,300 bags of dog food were to be recalled by a manufacturer due to the possibility that the food contained beef and meat by-products thought to have come from a BSE infected steer. Even though dogs cannot contract mad cow disease, the worry was that the dog food could accidentally be mixed into cattle or other animal feeds, which could then spread the disease.

The CFIA issued a statement that said, in part: "We wish to remind livestock producers not to mix dog food into cattle or other animal feeds. There is no scientific evidence that dogs can contract BSE or any similar disease. (N)or is there any evidence that humans can contract the disease through physical contact with the dry pet food."

Alfonso Torres, Associate Dean at Cornell University College of Veterinary Medicine, says: "There is no evidence that dogs have ever gotten the disease and there is no evidence that cats will contract the disease under normal circumstances."

An author of two books about feeding our dogs, Ann Martin, would disagree. She cites a case where Reuters European Business unearthed a 1991 study on the brains of 444 dead hunting hounds that suggested some of the animals had developed the first signs of a Spongiform disease. Further necropsies were not performed. Ms. Martin also cites a 1997 case wherein a Golden Retriever in Norway died from BSE-related brain damage and quotes Eivind Liven, Director of Norway's Animal Health Board, as telling the press that: "the dog had most likely contracted the prion disease from eating contaminated dog food."

(Note: I was personally unable to independently confirm these instances.)

Federal regulators go on to state: "There's no reason to worry about pets getting sick from pet food and no evidence to suggest any tainted meat has made its way into the pet food supply. There's never, ever been a reported case of a dog getting it."

Stephen Sundlof, Director of the Center for Veterinary Medicine at the FDA, says: "Some animals declared unfit for people can be used in pet food. But, they must be processed in such a way that they are deemed safe for the pets. This generally means that the food must be heat-treated or the animal-derived parts must be rendered to destroy any pathogens."

(Excuse, me, Mr. Sundlof, but didn't we just learn that prions are not destroyed by heat?)

Dr. Neils Pedersen, a specialist in feline infectious diseases at the School of Veterinary Medicine, University of California at Davis, says: "It would be highly unlikely that nervous tissue would end up even in pet food. It's one of those products that is as vigorously inspected and quality-controlled as canned tuna. In the U. S., pet food is closely inspected for quality and safety, in part because some of it ends up eaten by humans." Dr. Pederson is also the Director of both the Center for Companion Animal Health and the Veterinary Genetics Laboratory.

Since 1997, the U.S. has banned feeding cattle, sheep, and goats any food that contains the brain or spinal cord material from other livestock. The FDA asked for comments when it considered issuing a ban on using cattle brain and spinal tissues in food for dogs, cats, pigs and poultry. However, the U.S. government has not banned the use of these tissues in pet food or foods for non-livestock and as of July 2004, their final decision is still "pending."

Dr. Pedersen was also asked: "Could dogs contract BSE from chewing on rawhide toys or cows' hooves?"

He answered: "Again, that is highly, highly, unlikely. First, these particular tissues (skin and hooves) contain extremely low levels of prions, even if they came from an infected cow and would therefore not be very infectious even in the worst-case scenario. Second, dogs appear to be resistant* to the bovine prion disease. Third, except for the recent case, cattle in the U.S. had not had problems with BSE, greatly decreasing the likelihood of chews being contaminated."

(*Note: Dr. Pedersen said "resistant" and not "immune.")

There are virtually no Federal regulations having an independent checks and balances system impacting the choice, selection, or quality of ingredients used in commercial pet foods today.

Many veterinarians and scientists have recommended keeping dog food containing beef or any beef byproducts away from cats and from humans, both of whom may contract prion disease, based upon the old adage that an ounce of prevention is certainly worth the possibility of contracting a disease with no cure.

Ben Jones, President of the Association of American Feed Control Officials (AAFCO), recommends that meat and bone meal should be avoided altogether in any dog food products where there is the possibility of access by cats or kids.

Should I Feed Deer or Elk Meat to My Dog?

That's another question that has people scratching their heads. Most experts agree that dogs should be no more susceptible to Chronic Wasting Disease (CWD), a prion disease found in some deer and elk populations, than they are to BSE.

Chronic Wasting Disease is unique to North America and has been found in wild deer and elk and in captive deer and elk herds. It was first identified as a fatal wasting syndrome in captive mule deer in the late 1960s in a governmental research facility in Colorado and later was identified in mule deer in another research facility in Wyoming about 1978. It was first recognized in wild populations of elk and deer about 1981.

There are specific geographic areas of infection including, but not limited to, Wisconsin, Wyoming and Colorado. However deer and elk with CWD have also been discovered in New Mexico, Nebraska, South Dakota, Michigan, Oklahoma, Saskatchewan and Alberta. You can keep track of the progression of CWD throughout the U. S. and Canada on many websites dedicated to hunting and outdoor activities, as well as various state departments of game and wildlife.

CWD is probably transmitted through animal-to-animal contact, dam to fetus and/or contamination of feed or water with saliva, urine, or feces. However, no one knows for certain whether soil and water serve as hosts for the disease and if so, for how long prions can remain infective in these mediums.

Like BSE, CWD has a long incubation period and typically takes at least 16 months for an infected animal to show signs of illness. Symptoms of CWD include weight loss over weeks or months, behavioral changes, excessive salivation, difficulty swallowing, increased thirst and urination, head tremors, or convulsions. CWD is always fatal.

Although CWD does not appear to occur naturally outside the cervid family, it has been transmitted experimentally by injection into a number of laboratory animals including mice, ferrets, mink, squirrel monkeys and goats. However, it did not spread to cattle when they were orally challenged in laboratory conditions.

Currently, there is no indication that CWD is a threat to domestic animals and there have been no reports of CWD in dogs or in cats. There is ongoing research and, to date, there are no confirmed human neurological diseases linked to CWD. Therefore, many scientists and veterinarians believe it is safe to feed venison and elk to your dogs, cats, and family.

That being said, you should be informed that there is wide debate about a series of deaths that occurred in people who hunted deer and elk both in known endemic areas and outside those areas. Of 50 people identified as eating deer and elk at "wild game feasts" in a cabin owned by one of the decedents, two reportedly died of CJD and another died from another form of neurological disease. One decedent had only participated in the feasts on a single occasion. There are many interesting cases in the medical journals and scientists are looking for a variant or atypical type of neurological prion disease to explain these deaths.

Although the CDC suggests that the risk, if any, of transmission of CWD to humans is low, they do recommend that hunters minimize exposure to the CWD prion by:

As a precaution, hunters should avoid eating deer and elk tissues known to harbor the CWD agent, such as brain, spinal cord, eyes, tonsils, and lymph nodes. Some tissues thought to be negative for the infective agent include liver, bone marrow, skeletal muscle, and skin.

The Milwaukee Journal-Sentinel interviewed one of their local hunters, Kevin McCabe. He was in a quandary about what to do with 200 pounds of venison found to be positive for CWD following testing by the processing plant where he'd left the deer. Although he had field-dressed the animal himself, had he really been careful? Should he listen to the CDC and avoid eating the meat?

The story continued that, after much consideration, he decided he'd probably just eat the meat himself and not feed it to his family. His children vetoed that idea. So, he considered turning the 200 pounds of venison into dog food. Prior to bringing part of the meat home, Mr. McCabe consulted his wife, a veterinarian. She told him in no uncertain terms to keep the venison off their property – period.

Well known chef and cookbook author, Sara Dickerman, says: " Until I know more, venison from New Zealand, where every animal is tested and there's not been a single case of CWD, seems more appealing-and possibly safer-than home grown from the United States."

I'd like to know how the processing plant properly disposed of that venison. How do you safely get rid of CWD contaminated meat when no one knows whether those disease-causing prions remain in the soil? How long are prions in the soil a danger? And, can deer and elk become ill from the soil, alone, rather than from other animals?

Folks often allow their dogs to chew on antlers. Now, that may be something you want to research and rethink, or perhaps discuss with your veterinarian health care provider. Although it is thought to be extremely unlikely that your dogs could ever become ill, could those antlers possibly contaminate fresh soil, thus exposing greater numbers of the cervid family to infection?


I don't have many answers. The more I read, research, e-mail, and phone various experts, the more I find myself concentrating on the "loophole" words and phrases, such as: highly unlikely, perhaps, maybe, possible, probable, documented, nearly, estimated and my favorite – "appears but not scientifically proven, so we'll just say undocumented."

Overwhelmingly, scientists believe our human and dogs' food supply chain is safe from BSE and CWD, well, except in very rare instances. And, in those cases, it is the humans, not our dogs, who are not guaranteed 100 percent safety.

Other than those anecdotes reported by Ann Martin, I have found no documented cases of prion disease in dogs.

If I owned a kitty, or had children, I'd make certain there was no pet food containing beef or beef byproducts or beef meal in my home. I'd follow the recommendations of Ben Jones.

If I had venison or elk meat in my freezer, I'd call my local Department of Public Health and ask how to safely and permanently dispose of it. Perhaps you'd come to a different conclusion.

Each of us must make informed decisions for the well being of our families and our pets. For me, these decisions will be based upon:

Recently, a friend who feeds raw beef to her dogs organized friends into a food-buying co-op for pet owners. They contacted a local rancher who sells organic-certified beef and contracted to purchase scraps and bones on a regular basis, reducing not only their individual costs but their collective worries.

The jury is out on BSE and CWD. More is unknown than is certain. Knowledge is power; so update yours often.

January 25, 2005 – Author's Update

I originally researched and wrote this piece in July 2004. Since that time, several significant events have taken place:

FDA Center for Veterinary Medicine

Their most recent bulletin, dated November 4, 2004 explains evaluations of two commercial test kits designed to detect animal proteins in animal feed. Having an on-site testing method is extremely important and immediately relevant because in January 2005 a Canadian cow was discovered that had contracted BSE after their feed ban was in place.

Two Canadian Cows Tested Positive for BSE in January, 2005

Between January 3 and January 13, 2005, two additional cows have tested positive for BSE in Canada. The first cow, approximately eight years old, was given feed prior to food restriction bans. This case was not unexpected.

The second cow, however, is making headline news in both Canada and, to a lesser degree, the United States, because it was born after restrictions banning the feeding of animal proteins to cattle went into effect.

The infected cow was behaving "fairly normally" before it slipped and injured itself in late December (2004) prompting a call to the local veterinarian, who asked for euthanization and BSE testing as part of Canada's surveillance system. Tests came back positive for BSE.

Can you believe that feed restrictions, put into place in 1997, said that: "pre-ban feed can still be used until it runs out?" Many Canadian cattlemen estimated that could have taken up to three years.

On January 14, 2005, the Globe and Mail newspaper (Canada) reported that the search for the source of the latest mad cow case had come down to a readily available grain supplement an Alberta farmer bought nearly a year after strict new safeguards were put into place. The farmer, Wilheim Vohs, fed the supplement to 104 animals in his 1998 calf crop. Of that number 34 were used for breeding and the rest wound up in feedlots for slaughter.

The investigation into the contents of the supplement, its manufacturer and the mill selling it remains ongoing.

Ah, Politics…Quotes from Alberta's Premier re BSE

January 14, 2005: Alberta Premier Ralph Klein said: "BSE is overblown; the illness should be renamed BS."

Additional infamous advice given by Ralph Klein to cattlemen in Alberta if they should discover a BSE cow in their herd: "Shoot, shovel and shut up."

Controversy in Canada – Science and Politics

January 13, 2005 Editorial from the CBC states:

"It is a sad state of affairs indeed that forces Canadians to rely on Washington's assurance that Canadian beef is safe for Americans, and therefore safe for them to eat, too. But, that is the price we pay for our government's apparent willingness to put economic interests ahead of public health."

Toronto Star Editorial of January 10, 2005:

"As officials at the Canadian Food Inspection Agency scramble to find out it if was an isolated case of BSE, those three letters could again become a "Bad Sign for our Exports."

On January 20, 2005, an editorial in the Toronto Star newspaper said:

"Both Canada and the United States are relying on a feed ban to stop mad cow disease, but the effectiveness of the ban can be gauged only if there is widespread, comprehensive testing of cattle. No one knows yet how this young cow was infected or whether the ban was violated somehow."

To address the threat in cattle feed, the Canadian government has proposed a tighter ban on ruminant materials that would bar so-called specified risk materials from being used for ANY animal feed or in fertilizer. The highest risk cattle materials would be entirely out of circulation, although such things as blood, milk, gelatin and rendered fat could still be turned into feed for chickens and pigs.

The editorial went on to call for "Canadian and American cattle tested rigorously for the presence of mad cow disease."

United States announces plans to reopen the border for Canadian beef cattle The United States Department of Agriculture announced that the ban on live Canadian beef cattle under thirty months old will be lifted on March 7, 2005. Resolve to stick with this timetable, despite two additional cases of BSE in Canadian cattle in 2005, has led to vigorous objections by American cattle producers.

The United Stockgrowers of America –vs- USDA: Lawsuit filed January 10, 2005

On January 10, 2005 the group known as R-Calif., USA (R-Calif. United Stockgrowers of America) filed a federal lawsuit challenging the USDA's Final Rule on reopening the Canadian border to live cattle younger than 30 months and beef products from animals of all ages.

This lawsuit lists approximately seventy allegations aimed at proving that the USDA is being "arbitrary and capricious and abusing its discretion in failing to consider relevant information or response to public comments."

Plaintiffs are asking the court to force the USDA to:

"revise and seriously reconsider its determination that opening the US border to Canadian cattle and meat would present little risk to US animals, human consumers and the livestock industry with the United States."

For a complete transcript of the complaint go to:

United States Economics

Not only are American cattlemen upset because of public health reasons, they are trying to prevent what they believe could become an economic disaster if the ban on Canadian beef is lifted.

While Canadian beef was banned, American producers had a smaller base of competition along with increased demand. The discovery of two more Alberta cows infected with BSE just weeks before the ban is supposed to be lifted has given a scientific boost to their economic argument.

American beef producers believe that Japan is much less likely to lift its ban on United States beef when the United States allows Canadian cattle imports. The only BSE positive cow found within the United States hailed from Canada.

United States Senate Agriculture Committee Hearings

The United States Senate Agriculture Committee has scheduled meetings to begin on February 3, 2005, regarding whether beef trade restrictions with Canada should be lifted, as planned, on March 7, 2005.

And, Back to Dog Food and My Views

Currently, in the United States, no regulations exist regarding the content of dog food. Yet, it is a known that feed lots serve dog food to cattle.

Perhaps rules, regulations and regular testing for foods intended for canine consumption are needed not so much to protect dogs, who appear to be resistant or immune to BSE, but to protect the American beef industry and consumers.

The more information that I glean regarding BSE, the more it seems that action that should be based in science is influenced by politics and economics. So many factions have an agenda and there are powerful lobbying groups on both sides of the border.

Who is looking out for the consumer? How much confidence can Canadians muster when the Premier of Alberta recommends: "shoot, shovel and shut up?" Why must a lawsuit be filed in order to have Senate hearings and the USDA reconsider its dates for lifting the Canadian beef ban?

Can science and reasonable minds prevail in setting a responsible course of action that lessens the possibility of a BSE outbreak in North America?

February 06, 2005 – Author's Update

Infectious Agent Linked to Mad Cow Disease Found in Organs Other Than the Brain

Prions, infectious proteins associated with bovine spongiform encephalopathy (BSE) or Mad Cow Disease, were previously thought to accumulate mainly in the brain, but Yale and University of Zurich researchers report in Science that other organs can also become infected.

New Haven, Connecticut – Past research had shown that the brain and spinal cord bear the highest infection risk for BSE, followed by organs such as the spleen, lymph nodes and tonsils. All other organs were thought to be devoid of prions.

Ruddle and co-authors analyzed three organ systems that are typically free of prions: liver, pancreas and kidney, in five different mouse models of chronic inflammation. After the mice were infected with prions, the team detected prion accumulation in the inflamed organs. They concluded that the spectrum of organs containing prions might be considerably increased in situations of chronic inflammation.

"The study suggests that the current prion risk-classification of farm animal organs may need to be reassessed in animals suffering from inflammation due to microbial infection or autoimmune disease," said Nancy H. Ruddle, the John Rodman Paul Professor and Director of Graduate Studies in the Department of Epidemiology and Public Health at the Yale School of Medicine.

Previous research in Adriano Aguzzi's group at the Institute of Neuropathology at University of Zurich showed that B cells are essential for the spread of prions to organs other than the brain. B cells are found in lymphoid organs in healthy humans and animals, but they can migrate into non-lymphoid organs under inflammatory circumstances.

Other researchers on the study include first author Mathias Heikenwalder, Nicolas Zeller, Harald Seeger, Marco Prinz, Peter-Christian Klohn, Petra Schwarz, Charles Weissman and the director of the study, Adriano Aguzzi.

Ruddle's portion of this study was supported by National Institutes of Health Grant CA 16885.

Source: Science, Online Publication: January 20, 2005. Print Publication: February 18, 2005.


Information for this article has come from a variety of sources. These include, but are not limited to: