The U.S. Department of Agriculture announced Tuesday that it had identified a case of mad cow disease, the first in six years, in a dairy cow in central California — and the fact that the discovery was made at all was a stroke of luck.

The cow “was never presented for human consumption, so it at no time presented a risk to the food supply or human health,” John Clifford, chief veterinary officer at the department, said in a statement as he scrambled to reassure consumers around the world.

Luck of the draw

“We randomly pick a number of samples throughout the year, and this just happened to be one that we randomly sampled,” said executive vice president Dennis Luckey of Baker Commodities, the rendering plant where the cow was discovered on its way to be turned into pet food when it was diagnosed.

Tests are performed on only a small portion of dead animals. In fact, the number or cows tested for the fatal brain disease by the Agriculture Department surveillance program is a small fraction of the 90.8 million head of cattle in the US, and of that vast number only about 40,000 cows (less than half of 1%) are tested per year.

“We really don’t know if this is an isolated unusual event or whether there are more cases in U.S. beef,” Dr. Michael Hansen, senior scientist at Consumers Union, the advocacy arm of Consumer Reports. “Our monitoring program is just too small.”

Rare as hen’s teeth

According to Dr. Clifford the dairy cow was positive for “atypical BSE” (H-type), a very rare form of the disease “not generally associated” with an animal consuming infected feed. Atypical BSE differs from classic BSE in that cattle that have it are usually older and generally appear healthy.

It was “just a random mutation that can happen every once in a great while in an animal,” said Bruce Akey, director of the New York State Veterinary Diagnostic Laboratory at Cornell University. “Random mutations go on in nature all the time.”

“Are you worried about all of the meteors that passed the earth last night while you were sleeping? Of course not,” said James Culler, director of the UC Davis dairy food safety laboratory and an authority on BSE. “Would you pay 90 percent of your salaries to set up all of the observatories on earth to watch for them? Of course not. It’s the same thing.”

The Centers for Disease Control and Prevention estimates that the odds of a person contracting mad cow disease, even after consuming contaminated products, are less than one in 10 billion.

A nasty surprise

“This is an atypical case, which means it’s not connected in any way, shape or form to feed. A very rare circumstance and situation,” FDA Secretary Vilsack told CNN. “It can just sort of come up and pop up — sometimes it’s genetic.”

Experts say it’s unclear whether this rare type of BSE ever has been transmitted from a cow to a human by eating meat, although much of what is known about BSE in general is based on accepted hypothesis.

“Our best prevailing wisdom about this is that there may be a spontaneous form of this cow dementia,” said Dr. Will Hueston, a professor of public health at the University of Minnesota. “This new case appears to be that sporadic type of the disease, a sole cow that happens to get it at random and without any predictive characteristics.”

Atypical BSE is thought to be either a genetic mutation that randomly springs from nature’s library of anomalies or that the gene was inherited.

In other words, the genes that mutated into atypical BSE could have erupted spontaneously or the gene was passed to that cow from another cow carrying the disease. Where the cow’s ancestors are is a complete mystery, as the USDA does not track herds, so it would be impossible to determine where the other infected cattle came from or where they end up — a fact the USDA would not like the public to contemplate.

You can’t cook a prion

Since prions aren’t alive in any sense of the word they’re resistant to forms of sterilization that inactivate infectious agents like viruses, bacteria, and fungi. And prions escape the normal high-temperature rendering process used to transform otherwise inedible tissues into “meat-and-bone meal” (aka mystery meat), a common constituent of pet food and livestock feed.

Dr. Clifford’s reassurance that the, “USDA also bans all non-ambulatory (sometimes called a “downer”) cattle from entering the human food chain,” and “for animal health, the Food and Drug Administration (FDA) ban on ruminant material in cattle feed prevents the spread of the disease in the cattle herd”, was not an especially comforting or relevant assurance; particularly as the dairy cow in California tested positive for atypical BSE (which are cows that are usually older and generally appear healthy), suggests that cows that have atypical BSE who can walk to the slaughterhouse on their own steam avoid the “downer” clause.

Third-world countries are better at it than we are

The USDA’s pre-emptive strike to quell the public criticism surrounding around the BSE positive cow was short-lived. Shortly following the USDA press announcement the Center for Science in the Public Interest (CSPI) observed that,

“A case of a single cow with Bovine Spongiform Encephalopathy is not a reason for significant concern on the part of consumers, and there is no reason to believe the beef or milk supply is unsafe.   

If the cow were exposed to the typical strain of BSE via animal feed—and the government says that’s not the case here—that would have represented a significant failure.  The government’s ability to track down other cattle that may have been exposed via feed would have been hampered without an effective animal I.D. program.   

The United States has first-world resources and technology but a third-world animal identification system.  In fact, some third-world countries do a better job of tracking livestock than America does.  Botswana, for one, uses RFID microchips to track its animals up and down the supply chain.  If American cattlemen suffer economic losses at the news of this discovery of BSE, they should blame only themselves and other opponents of a mandatory animal identification system. “

Silent carriers

However, new evidence suggests that the entire accepted theory of where the deadly BSE prions reside into question.

A recent study published in the journal Science in January suggested the futility of safeguards:

“The deadly brain diseases known as prion diseases might pass from one species to another more easily than previously thought, a new study from France finds.

Prions, such as those that cause “mad cow” disease [BSE], spread via exposure to infected lymphoid tissues — such as the spleen or lymph nodes — more easily than they can through exposure to infected brain tissues, the study showed.

The finding suggests that the number of animals or people that are “silent carriers” of prion diseases may be higher than previously thought.”

“Prion proteins can multiply quite efficiently in the lymphoid tissue,” Beringue said. “This was totally overlooked until now, most likely because studies were focused on brain tissue,” he said.

The study has significant implications for public and animal health, according to Christina Sigurdson, who researches prion diseases at the University of California at San Diego, and was not involved with the study.

For example, Sigurdson said, chronic wasting disease is a prion disease found in deer and elk, and is currently spreading in these animals throughout the United States, according to the CDC.

“Although there is evidence of a species barrier for human infection with this disease, we don’t know if there is a population of people that may be currently infected with deer or elk prions,” she said.

“This is a major concern, because the infection could remain undetected for long periods of time,” she added.

A time bomb

It is generally accepted that incubation period between consuming beef contaminated with BSE to vCJD is 10-12 years. There exists strong epidemiologic and laboratory evidence for a causal association between a new human prion disease called variant Creutzfeldt-Jakob disease (vCJD) that was first reported from the United Kingdom in 1996 and the BSE outbreak in cattle. The interval between the most likely period for the initial extended exposure of the population to potentially BSE-contaminated food (1984-1986) and the onset of initial variant CJD cases (1994-1996) is consistent with known incubation periods for the human forms of prion disease.

Because of the spontaneous and inherited etiology of BSE, eradication is not an attainable goal and a low incidence of BSE can be expected to persist within the cattle population.

A really stupid idea

The ban of cow’s brains and spinal cords in feed has been cited again and again by Agriculture Department and industry spokesmen as some sort of guarantee that mad cow has not taken hold in the United States. Unfortunately, this safeguard may have gaps big enough to let a herd of steer wander through it.

The current ban still allows the feeding of cattle blood to young calves — a practice that Stanley Prusiner, who won the Nobel Prize in medicine for his work on the proteins that cause mad cow disease, calls ”a really stupid idea.”

Got blood?

Over a decade ago the European Commission concluded that as far as ruminant blood is concerned, the best approach to protect public health is “to assume that it could contain low levels of infectivity”. Since that time evidence that blood can be infectious has only grown, yet dairy calves in the United States are still drinking up to three cups of “red blood cell protein” concentrate every day.

Blood, shit and tears

Perhaps the mad cow discovery in a California dairy cow will renew interest in closing the loopholes in feed regulations that continue to allow the feeding of slaughterhouse waste, blood and manure to farm animals and pets in the United States.

As such, there is not a safeguard in existence that could protect the future of humans and animals from a deadly disease that remains hidden for years, waiting…silently.

Government references

Statement by USDA Chief Veterinary Officer John Clifford Regarding a Detection of Bovine Spongiform Encephalopathy (BSE) in the United States
Video of an interview with USDA’s Chief Veterinary Officer John Clifford on the BSE case
Statement by U.S. Agriculture Secretary Tom Vilsack Regarding a Detection of Bovine Spongiform Encephalopathy (BSE) in the United States
CDC on BSE (Bovine Spongiform Encephalopathy, or Mad Cow Disease)
BSE and the Safety of Pets
Substances Prohibited From Use in Animal Food or Feed; Final Rule / 21 CFR Part 589 / Federal Register / Vol. 73, No. 81 / Friday, April 25, 2008
USDA Livestock Slaughter statistics in 2011

Non-Government references

Brain Diseases May Spread from Animals to Humans More Easily than Thought
Mad Cow California: Stop Weaning Calves on Cattle Blood