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A UM researcher answers frequently asked questions about Mad Cow Disease and talks about an effort he's heading to develop a quick and inexpensive test for prion diseases.
Niel Constantine, Ph.D.
Concerned about Mad Cow Disease? If so, you're not alone. With the first case of Mad Cow Disease reported in the United States in mid December, the awareness of and concern about this disease have reached record levels. Recent recalls of meat from a number of states, and economically-devastating international bans on beef exports from the United States have shown what just one case of the deadly disease can cause.
Improve your Mad Cow Disease IQ by reading the following interview with Niel Constantine, Ph.D., a Professor of Pathology at the University of Maryland School of Medicine and the Director of the Clinical Immunology Laboratory. Dr. Constantine is heading a research effort funded by the Department of Defense to develop a quick and inexpensive screening test for prion diseases in animals and humans -- of which Mad Cow Disease is one.
What is Mad Cow Disease?
Mad Cow Disease is one of a series of prion diseases - fatal neurological diseases caused by an [abnormal confirmation] of the prion protein. Prion diseases have been known to occur for about 300 years, first occurring in sheep in a condition called scrapie, although the cause was unknown at the time. Prion diseases have now been described in a number of animals, including cows, cats, deer, elk, and others. In humans, it causes Creutzfeldt-Jacob disease (CJD), which occurs spontaneously in 1 in 1 million persons but can also be passed on genetically.
In the mid '80s, cows in the United Kingdom (UK) started presenting with this neurologic disease, where they would stumble and have neurologic symptoms. As they looked at the brains of these animals they found that they had the same type of changes that had been seen in sheep and also in the human form of CJD, a deadly brain illness that usually effects those over the age of 60. This disease in cows was called Bovine Spongiform Encephalopathy (BSE), and that is the Mad Cow Disease that is thought to have originated from the sheep disease scrapie, when cows were fed rendered products from sheep.
The disease in cows in the UK peaked in the late '80s, and in 1995 the first case of a new form of CJD in humans occurred in the UK, but it was different from the sporadic form of CJD that has been described elsewhere in the world because this occurred in younger people and had a different clinical course. It was very unusual, so the connection was possibly made between the cows that had contracted Mad Cow Disease and five to 10 years later humans came down with a variant form of CJD. This variant CJD (vCJD) has continued over the past decade, and about 140 cases of variant CJD have occurred, almost all in the UK.
In terms of how humans get it, is it just a matter of eating the meat of an infected cow?
For variant CJD, the answer is yes. There's no absolute proof, but it's assumed that the disease in humans was passed from cows by the eating of contaminated beef from a cow with BSE. Now whether the prion is actually in the beef itself or the prion contaminated the beef from nearby nervous tissue is unknown. But it has been verified that if one gram of infected cow brain is consumed by another cow, transmission will occur.
What makes Mad Cow Disease so dangerous?
The scary parts are that there is no treatment, no cure, and it's 100% fatal. And even the name Mad Cow Disease for some reason just scares people. But it is deadly, because once contracted there is nothing that can be done for the progression of tremors, loss of eyesight, loss of bodily function, dementia, and respiratory arrest.
With the first case of Mad Cow Disease in the United States, many people are worried about eating beef. In your opinion, is this something Americans should be concerned about?
Concerned, yes, panicky, no. There is only a very remote chance that infected beef actually gets to the consumer because of the way beef is processed (without brain and nervous tissue). Although it cannot be stated that there is zero chance, it is highly unlikely. I do not feel people should stop eating beef; I think the USDA and other regulatory authorities are taking the necessary steps now to ensure as best they can that potentially infected beef is removed, or at least concern is alleviated with these recalls.
What are the biggest misconceptions about Mad Cow Disease?
One misconception is that some people think if you cook beef that makes it safe. That's absolutely untrue because the prion protein can survive extremely high temperatures, so cooking will not protect anyone from this abnormal prion protein. Another misconception is that lamb can transmit the disease to humans; there's never been any evidence that this can occur.
Some reports have indicated that some vaccines given to kids have been made with products that could carry variant CJD or Mad Cow Disease. Is that true?
Those reports are true. There were some measles vaccines taken off the market in France because some of those vaccines were suspected to have been made with bovine products that are commonly used in vaccine preparations. Authorities, including the U.S. FDA, are scrutinizing how vaccines are made and how those products have been obtained, but the concerns about vaccines have lessened because of strict regulations about the use of bovine products.
Until recently, reported cases of Mad Cow Disease occured in other countries, including the UK. Do you recommend people traveling overseas take any precautions?
No. I was in the UK twice recently, and I have no concerns about eating beef; I love hamburgers. The incidence of Mad Cow Disease is certainly declining, as is the rate of new infections of variant CJD. This is undoubtedly due to the changes in feeding cattle meals made from other animal parts, including brain, that was the cause of the epidemic. There is no reason to believe that travel to any country would increase the risk of acquiring variant CJD.
Talk about the research you and others are involved with to develop a quick and inexpensive screening test for prion diseases in animals and humans.
Our history with prion diagnostics began in 2000, with funding from a commercial source to develop a blood test for prion protein. Since then, we have continued our research under a grant from the Department of Defense, which is concerned about military who were stationed overseas during the BSE epidemic. We have made excellent progress over the past three years, and will be presenting our findings at the Cambridge Healthtech Institute's eighth annual Transmissible Spongiform Encephalopathies Conference in Washington, DC in February 2004.
Our project is to develop a blood-screening test for animals and humans to be able to detect prion disease before animals and humans come down with symptoms. Right now, to diagnose the disease, you must have a brain biopsy from an animal or human. So there's no current way before symptoms appear to diagnose the disease. The objective of our study is to develop a test that could screen populations of animals and humans, for example blood donors, to be sure that they are not incubating the disease.
It appears that the prion protein is present in blood because transmission has been shown to occur in sheep that have been transfused from infected sheep. However, currently available tests that can detect prion in brain (where it is in high levels) cannot detect prion in blood; the tests are just not sensitive enough. So, we've devised several techniques that can detect ultra-low levels of prion protein, such that probably occur in blood. Our method exploits a combination of two highly sensitive techniques to produce one that is able to detect protein levels several thousand fold to a million fold lower than current methods. The test costs only $7 to perform, and requires one full day, although we are working on decreasing the time to less than a few hours.
How big a breakthrough will such a screening test be?
The availability of such a "live" blood test will be enormous. If a test is effective in being able to detect Mad Cow Disease during the incubation period well enough in advance of symptoms, we have a much better chance of protecting both beef and the blood supply. Consider that in the United States alone we screen 15 million blood units a year, and there are 100 million head of cattle, so that's perhaps a billion-dollar business just in this country. And, ensuring that beef and blood are safe will save not only dollars, but decrease the concern of the public.
Any idea when such a test might be available?
We've made great progress, and are very encouraged by our results. I would say we are nearing the time when we should be speaking with a major manufacturer about taking our test to the next step in the pathway to commercialization.
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