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USA Strain of Mad Cow Disease Suggests Widespread Contamination in U.S. Herds
US 'Atypical' Mad Cow Threat Was Predicted
By John Stauber
Center for Media and Democracy, June 14, 2006
http://www.prwatch.org/node/4883
The small scientific world of prion researchers -- the scientists who investigate "transmissible spongiform encephalopathies" (TSE) such as mad cow disease in cattle and Creutzfeldt-Jakob Disease (CJD) in humans -- is abuzz. That's because the two confirmed cases of US mad cow disease in Texas and Alabama are an "atypical" strain different from the British strain. This really should not be surprising. Sheldon Rampton and I reported in 1997 that very strong evidence of an "atypical" TSE disease in US cattle goes back to the 1985 work of Dr. Richard Marsh, the researcher to whom we dedicated our book Mad Cow USA. Even before Britain confirmed its first case of mad cow, Marsh was investigating a similar disease he traced to Wisconsin dairy cattle, confirming suspicions among US scientists since the 1960s that a deadly TSE disease in mink -- transmissible mink encephalopathy or TME -- resulted from their eating dairy cattle.
Marsh investigated an outbreak of TME on a mink ranch in Stetsonville, Wisconsin, in 1985. Here below is our report on Marsh's discovery of an atypical strain of BSE in US cattle from our 1997 book Mad Cow USA. (You can order the book for free from your favorite library and it is for sale in the usual places.) ### (Excerpted from Mad Cow USA, by Sheldon Rampton and John Stauber, pages 154-156
The common denominator in all of these [transmissible mink encephalopathy - TME] outbreaks was either "cattle" or "unknown." It was possible, of course, to imagine other scenarios, but Marsh believed he had at least strong circumstantial evidence that a TSE similar to mad cow disease already existed in U.S. cattle. "You can trace it back to feed real easy in mink," Marsh said. "And then you're left with the question, what was it in the feed that affected them? And what we find is it's these downer cows that are the common link. You don't have to be a genius to figure it out." Within the field of veterinary medicine, "downer cow syndrome" was a "garbage can" category, used indiscriminately as the official diagnosis for any animal that died or had to be put down after failing to stand on its own legs for 24 hours or more. These included cows suffering from paralysis, arthritis,grass tetany, ketosis, bone fractures, and a form of calcium deficiency known as "milk fever." Most downer cows died from causes unrelated to the spongiform encephalopathies, but it was possible that the generic nature of the classification enabled some TSE-infected cows to slip into the mix.
It was impossible in practice to absolutely prove the link between downer cows and transmissible mink encephalopathy. By the time the disease appeared in mink, any cow that might have been the source would be long gone, its tissues unavailable for testing. To test his theory, therefore, Marsh did the next best thing that had died in the Stetsonville outbreak. He puréed the brain in a blender and used hypodermic syringes to inject the homogenized liquid into test animals: fourteen healthy mink, eight ferrets, two squirrel monkeys, twelve hamsters, forty-five mice and two Holstein bull calves. The mice, remarkably, all stayed healthy, but every other species proved susceptible. The mink went down first, four months after inoculation. The two monkeys were the next to show neurological signs, at months nine and thirteen respectively. Two of the twelve hamsters survived, but the other ten succumbed in the fifteenth and sixteenth months. The two calves went down in months eighteen and nineteen. The ferrets lasted longest, but eventually the disease emerged in all but one of them, with incubation periods ranging between twenty-eight and thirty-eight months. These species barrier effects corresponded closely to the results from experiments with previous mink outbreaks.
Cattle are expensive test animals, and Marsh's experiments marked the first time that cattle had been tested for susceptibility to transmissible mink encephalopathy. His results proved that cattle could get the mink disease, and in turn led to unexpected new questions. "The real surprise of this experiment is that the clinical signs were quite different from what we've seen in Great Britain," he said. "This is what's changed our perspective on a surveillance of BSE in the United States. We thought BSE in the U.S. would look like BSE in Great Britain ioral changes, become aggressive and look very much like a rabies infection does in cows."
Marsh's bull calves showed none of the unusual "mad" behavior that emerged as early warning signs in British cattle. "Eighteen months after inoculation, one animal simply collapsed in its holding room and could not be returned to a standing position," he reported. "This animal had shown no previous signs of behavioral change or loss of body condition. . . . The second animal was normal until nineteen months after inoculation when it too sud- denly collapsed." Indeed, the test bulls behaved exactly like downer cows mals which the Stetsonville rancher had been feeding to his mink. "The most disturbing finding of all is that they have very minimal spongiform lesions in their brains," Marsh said. In previous experiments with mink, he had shown that the spongy holes in brains were a secondary effect of the disease which did not always appear in noticeable quantities. Some mink breeds infected with TME would develop all of the usual clinical symptoms, but upon autopsy their brains showed a marked lack of spongiform degeneration. Now it appeared that cattle could also develop a form of TSE without the telltale lesions to aid in diagnosis. Their symptoms would look like downer cow syndrome, and even a brain autopsy might find nothing out of the ordinary. "Without the brain lesions, the best way to diagnose the infection is a pro- tein in the brain," Marsh said. "But there are only a few labs in the country that can look for this protein. This is not something that can be done by the local veterinarian or even most state diagnostic laboratories. You need to havepretty sophisticated means of testing. This is going to complicate our efforts at surveillance and testing for BSE in thiscountry." Histopathology and immunohistochemistry tests confirmed that Marsh's bulls had died of a spongiform encephalopathy, but it was a different strain of spongiform encephalopathy than the one that was killing cows in England. Its behavior in test animals showed significant differences also. In England, mice succumbed when exposed to brain tissue from mad cows, but hamsters seemed immune. In Marsh's experiments with the Stetsonville isolate of TME, the pattern was exactly the opposite: mice lived, but hamsters died. To test whether passage through cattle altered the characteristics of the Stetsonville isolate, Marsh injected another 45 mice with brain tissue from his two test bulls. They also stayed healthy, just like the mice he had previously injected with mink brains. By itself, the fact that mink encephalopathy could infect cows was not terribly significant or surprising. After all, scientists had previously shown that TME could be transmitted to a wide variety of other test animals. What was significant was the result when Marsh took the brains of the dead bulls and used them on further tests with healthy mink. When backpassaged into mink, the bull brains behaved exactly the way mink brains behaved, causing symptoms of TME to emerge within four months after exposure by inoculation, or within seven months after oral exposure. "There was no evidence for any deadaptation of the bovine agent for mink compared to . . . non-bovine-passaged mink brain," Marsh observed. "This suggests that there are no species barrier effects between mink and cattle in relation to the Stetsonville source of TME" more evidence pointing to cattle as the source of the infection. "If mink on the Stetsonville ranch were exposed to TME by feeding them infected cattle, there must be an unrecognized scrapie-like disease of cattle in the United States," Marsh concluded. "If this is true, the disease is rare. The low incidencerate of TME and the fact that the Stetsonville mink rancher had fed products from fallen or sick cattle to his animals for the past 35 years suggests a very low prevalence of this disease." The rarity of the disease, however, did not mean that it posed no danger. In fact, it could mean the very opposite. Mad cow disease had also been rare once in England. The very fact that it was rare, combined with its slow incubation period, were the factors that prevented the British from recognizing its dangers until it had already infected tens of thousands of animals. Moreover, the British had an advantage that U.S. farmers might not enjoy. Their strain of bovine spongiform encephalopathy was picked up fairly soon once cattle started behaving strangely. If a different strain of BSE existed in U.S. cattle a strain where the animals didn't act deranged but simply fell over, like thecows in Marsh's tests conceivably go unrecognized for a long time, invisible within the larger population of U.S. downer cows. Every year, some 100,000 U.S. cows get classified as downers. Marsh was not suggesting that all 100,000 were carriers of a spongiform encephalopathy. What concerned him was the possibility that downer cow syndrome could mask the emergence of a TSE in the cattle population, allowing the disease to invisibly spread until it reached dangerous levels. It could multiply the same way it had multiplied in England, as rendering plants recycled the infection by converting sick animals into meat and bone meal which was then fed back to other cattle. The only certain way to prevent a cattle epidemic, therefore, would be to adopt the same policy that the British had already been forced to adopt: ban the practice of feeding rendered cows and other ruminant ani- mals back to members of their own species. ### (End of excerpt)
Today the ability to test for mad cow disease strains has greatly advanced, and so-called rapid tests are used on all cattle before they are allowed into the human food chain in Japan, for instance. In the United States I continue to describe the situation here as a cover-up of the extent of infection with mad cow disease because the US needs to test millions of cattle a year, and in a transparent and verifiable way, and it is not. In addition, despite the false PR assurances from government and the livestock industry, there is no "firewall feed ban" in the United States to completely stop the spread of mad cow disease.
US 'Atypical' Mad Cow Threat Was Predicted
By John Stauber
Center for Media and Democracy, June 14, 2006
http://www.prwatch.org/node/4883
The small scientific world of prion researchers -- the scientists who investigate "transmissible spongiform encephalopathies" (TSE) such as mad cow disease in cattle and Creutzfeldt-Jakob Disease (CJD) in humans -- is abuzz. That's because the two confirmed cases of US mad cow disease in Texas and Alabama are an "atypical" strain different from the British strain. This really should not be surprising. Sheldon Rampton and I reported in 1997 that very strong evidence of an "atypical" TSE disease in US cattle goes back to the 1985 work of Dr. Richard Marsh, the researcher to whom we dedicated our book Mad Cow USA. Even before Britain confirmed its first case of mad cow, Marsh was investigating a similar disease he traced to Wisconsin dairy cattle, confirming suspicions among US scientists since the 1960s that a deadly TSE disease in mink -- transmissible mink encephalopathy or TME -- resulted from their eating dairy cattle.
Marsh investigated an outbreak of TME on a mink ranch in Stetsonville, Wisconsin, in 1985. Here below is our report on Marsh's discovery of an atypical strain of BSE in US cattle from our 1997 book Mad Cow USA. (You can order the book for free from your favorite library and it is for sale in the usual places.) ### (Excerpted from Mad Cow USA, by Sheldon Rampton and John Stauber, pages 154-156
The common denominator in all of these [transmissible mink encephalopathy - TME] outbreaks was either "cattle" or "unknown." It was possible, of course, to imagine other scenarios, but Marsh believed he had at least strong circumstantial evidence that a TSE similar to mad cow disease already existed in U.S. cattle. "You can trace it back to feed real easy in mink," Marsh said. "And then you're left with the question, what was it in the feed that affected them? And what we find is it's these downer cows that are the common link. You don't have to be a genius to figure it out." Within the field of veterinary medicine, "downer cow syndrome" was a "garbage can" category, used indiscriminately as the official diagnosis for any animal that died or had to be put down after failing to stand on its own legs for 24 hours or more. These included cows suffering from paralysis, arthritis,grass tetany, ketosis, bone fractures, and a form of calcium deficiency known as "milk fever." Most downer cows died from causes unrelated to the spongiform encephalopathies, but it was possible that the generic nature of the classification enabled some TSE-infected cows to slip into the mix.
It was impossible in practice to absolutely prove the link between downer cows and transmissible mink encephalopathy. By the time the disease appeared in mink, any cow that might have been the source would be long gone, its tissues unavailable for testing. To test his theory, therefore, Marsh did the next best thing that had died in the Stetsonville outbreak. He puréed the brain in a blender and used hypodermic syringes to inject the homogenized liquid into test animals: fourteen healthy mink, eight ferrets, two squirrel monkeys, twelve hamsters, forty-five mice and two Holstein bull calves. The mice, remarkably, all stayed healthy, but every other species proved susceptible. The mink went down first, four months after inoculation. The two monkeys were the next to show neurological signs, at months nine and thirteen respectively. Two of the twelve hamsters survived, but the other ten succumbed in the fifteenth and sixteenth months. The two calves went down in months eighteen and nineteen. The ferrets lasted longest, but eventually the disease emerged in all but one of them, with incubation periods ranging between twenty-eight and thirty-eight months. These species barrier effects corresponded closely to the results from experiments with previous mink outbreaks.
Cattle are expensive test animals, and Marsh's experiments marked the first time that cattle had been tested for susceptibility to transmissible mink encephalopathy. His results proved that cattle could get the mink disease, and in turn led to unexpected new questions. "The real surprise of this experiment is that the clinical signs were quite different from what we've seen in Great Britain," he said. "This is what's changed our perspective on a surveillance of BSE in the United States. We thought BSE in the U.S. would look like BSE in Great Britain ioral changes, become aggressive and look very much like a rabies infection does in cows."
Marsh's bull calves showed none of the unusual "mad" behavior that emerged as early warning signs in British cattle. "Eighteen months after inoculation, one animal simply collapsed in its holding room and could not be returned to a standing position," he reported. "This animal had shown no previous signs of behavioral change or loss of body condition. . . . The second animal was normal until nineteen months after inoculation when it too sud- denly collapsed." Indeed, the test bulls behaved exactly like downer cows mals which the Stetsonville rancher had been feeding to his mink. "The most disturbing finding of all is that they have very minimal spongiform lesions in their brains," Marsh said. In previous experiments with mink, he had shown that the spongy holes in brains were a secondary effect of the disease which did not always appear in noticeable quantities. Some mink breeds infected with TME would develop all of the usual clinical symptoms, but upon autopsy their brains showed a marked lack of spongiform degeneration. Now it appeared that cattle could also develop a form of TSE without the telltale lesions to aid in diagnosis. Their symptoms would look like downer cow syndrome, and even a brain autopsy might find nothing out of the ordinary. "Without the brain lesions, the best way to diagnose the infection is a pro- tein in the brain," Marsh said. "But there are only a few labs in the country that can look for this protein. This is not something that can be done by the local veterinarian or even most state diagnostic laboratories. You need to havepretty sophisticated means of testing. This is going to complicate our efforts at surveillance and testing for BSE in thiscountry." Histopathology and immunohistochemistry tests confirmed that Marsh's bulls had died of a spongiform encephalopathy, but it was a different strain of spongiform encephalopathy than the one that was killing cows in England. Its behavior in test animals showed significant differences also. In England, mice succumbed when exposed to brain tissue from mad cows, but hamsters seemed immune. In Marsh's experiments with the Stetsonville isolate of TME, the pattern was exactly the opposite: mice lived, but hamsters died. To test whether passage through cattle altered the characteristics of the Stetsonville isolate, Marsh injected another 45 mice with brain tissue from his two test bulls. They also stayed healthy, just like the mice he had previously injected with mink brains. By itself, the fact that mink encephalopathy could infect cows was not terribly significant or surprising. After all, scientists had previously shown that TME could be transmitted to a wide variety of other test animals. What was significant was the result when Marsh took the brains of the dead bulls and used them on further tests with healthy mink. When backpassaged into mink, the bull brains behaved exactly the way mink brains behaved, causing symptoms of TME to emerge within four months after exposure by inoculation, or within seven months after oral exposure. "There was no evidence for any deadaptation of the bovine agent for mink compared to . . . non-bovine-passaged mink brain," Marsh observed. "This suggests that there are no species barrier effects between mink and cattle in relation to the Stetsonville source of TME" more evidence pointing to cattle as the source of the infection. "If mink on the Stetsonville ranch were exposed to TME by feeding them infected cattle, there must be an unrecognized scrapie-like disease of cattle in the United States," Marsh concluded. "If this is true, the disease is rare. The low incidencerate of TME and the fact that the Stetsonville mink rancher had fed products from fallen or sick cattle to his animals for the past 35 years suggests a very low prevalence of this disease." The rarity of the disease, however, did not mean that it posed no danger. In fact, it could mean the very opposite. Mad cow disease had also been rare once in England. The very fact that it was rare, combined with its slow incubation period, were the factors that prevented the British from recognizing its dangers until it had already infected tens of thousands of animals. Moreover, the British had an advantage that U.S. farmers might not enjoy. Their strain of bovine spongiform encephalopathy was picked up fairly soon once cattle started behaving strangely. If a different strain of BSE existed in U.S. cattle a strain where the animals didn't act deranged but simply fell over, like thecows in Marsh's tests conceivably go unrecognized for a long time, invisible within the larger population of U.S. downer cows. Every year, some 100,000 U.S. cows get classified as downers. Marsh was not suggesting that all 100,000 were carriers of a spongiform encephalopathy. What concerned him was the possibility that downer cow syndrome could mask the emergence of a TSE in the cattle population, allowing the disease to invisibly spread until it reached dangerous levels. It could multiply the same way it had multiplied in England, as rendering plants recycled the infection by converting sick animals into meat and bone meal which was then fed back to other cattle. The only certain way to prevent a cattle epidemic, therefore, would be to adopt the same policy that the British had already been forced to adopt: ban the practice of feeding rendered cows and other ruminant ani- mals back to members of their own species. ### (End of excerpt)
Today the ability to test for mad cow disease strains has greatly advanced, and so-called rapid tests are used on all cattle before they are allowed into the human food chain in Japan, for instance. In the United States I continue to describe the situation here as a cover-up of the extent of infection with mad cow disease because the US needs to test millions of cattle a year, and in a transparent and verifiable way, and it is not. In addition, despite the false PR assurances from government and the livestock industry, there is no "firewall feed ban" in the United States to completely stop the spread of mad cow disease.
