The downer dairy cow recently found stricken with mad cow disease in California was infected with an “atypical” strain. Such cases are thought to arise spontaneously, a notion the USDA seized upon to explain how the disease could arise despite their regulations. If anything, that fact highlights the weaknesses in the current feed rules. If mad cow disease can arise out of nowhere, then it’s even more important to close the loopholes and stop the feeding of cattle blood to calves and chicken manure to cows to prevent it from spreading. And what the USDAdidn’t mention about the atypical strain found in California is that there’s evidence it’s a more dangerous form of the disease
The California cow died of a particularly virulent form of mad cow disease known as BASE, bovine amyloidotic spongiform encephalopathy, also known as L-type atypical BSE. Typical BSE was first documented in the ’80s in Britain. Afflicted cows often became twitchy and aggressive, giving rise to the “mad cow disease” moniker, as their brains degenerated into a characteristic Swiss cheese-like appearance. Hence the scientific name, BSE: bovine (cow) spongiform (sponge-like) encephalopathy (brain disease).
Then cats started dying. Max, someone’s pet Siamese, was the first non-bovine victim of the disease. Infectious pet food was implicated as the cause of Max’s death from a never-before-described felinespongiform encephalopathy.
Then young people started succumbing to a human spongiform encephalopathy called Creutzfeldt-Jakob disease, a relentlessly progressive and invariably fatal dementia, often involving weekly deterioration into blindness and seizures as their brains became riddled with holes. CJD appears sporadically in one in a million people, but typically strikes only the elderly. The new cases among teenagers were dubbed “variant” CJD, a disease now understood to be caused by consuming contaminated meat (or by getting a blood transfusion from someone who did).
Despite massive contamination of the food supply, no more than a few thousand people are expected to die, suggesting a robust transmission barrier between cows and humans when it comes to BSE. The same may not be true of the atypical forms of BSE found in California and in the last two mad cows in Texas and Alabama. Experimental models of human infection suggest that the type of mad cow disease discovered in the California case “is a more virulent BSE strain… in humans,” with “higher transmissibility” and causing a swifter death.
Just as one in a million people sporadically get CJD, evidence suggests one in a million cattle get atypical BSE. The U.S. cattle population hovers around 100 million. Though there is evidence some of these sporadic human cases of CJD may be associated with infected cows or sheep, case control studies tie CJD more closely to the consumption of pork. A study co-authored by D. Carleton Gajdusek, recipient of the Nobel Prize in Medicine for his research on these diseases, found that “consumption of pork as well as its processed products (e.g., ham, scrapple) may be considered as risk factors in the development of Creutzfeldt-Jakob disease.”
Though pigs have been proven susceptible to a porcine spongiform encephalopathy, the National Pork Producers Council claims that no naturally occurring cases of “mad pig” disease have ever been discovered. The Consumers Union, publisher of Consumer Reports, however, has petitioned the federal government to reopen an investigation into a case in which a USDA veterinarian may have found a cluster of suspect pigs in upstate New York.
New research just found that unlike the British strain, the atypical forms of BSE found in the U.S. cause animals to have difficulties in standing up, so instead of mad cow disease, it’s more of a downer cow disease. Since we continue to feed slaughterhouse waste and blood to pigs, this raises the question whether any of the hundreds of thousands of downed pigs that arrive at slaughter plants every year in the U.S. may be infected.
It’s ironic that this new case of mad cow disease was discovered in California where a law excluding downed animals from the food supply was recently overturned by the Supreme Court.
In 2008, an undercover investigation by The Humane Society of the United States of a dairy cow slaughterplant in California showing that downers were being dragged to slaughter for school lunch hamburgers prompted California to strengthen its laws to keep downer livestock out of the food supply. The meat industry, represented by the National Meat Association and the American Meat Institute, responded by successfully suing the state of California to keep meat from downed animals on people’s plates on the grounds that only USDA had the authority to determine which animals should not be forced to the kill floor for humane or public health reasons.
Sick animals can lead to sick people. An unequivocal ban on the slaughter of any farm animal unable even to stand may reduce the public health risk of myriad threats from anthrax and E. coli to swine flu andSalmonella. Spongiform encephalopathies are a special case, though, as they are caused by infectious agents that cannot be eliminated by cooking, pasteurization, or the rendering process used to make pet food. In fact, infection can survive even incineration at temperatures hot enough to melt lead. It is therefore the meat industry’s responsibility to prevent sick animals from entering the food chain in the first place, by instituting a “bright line” ban on the slaughter of all downed livestock. In the California case, the animal was killed before she could be slaughtered. Next time we might not be so lucky.
Michael Greger, MD, is Director of Public Health and Animal Agriculture at The Humane Society of the United States.
This column originally appeared on Huffington Post.