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by
Susan Schoenian
Area Agent, Sheep and Goats Western Maryland Research & Education Center Maryland Cooperative Extension Date created or last revised: 23-Dec-2005 |
UPDATE: This article was written in 2000. In December 2003, the first case of mad cow disease was found in the U.S. The sick animal came from a farm in Washington State. A second case was confirmed in June 2005. BSE was NEVER confirmed in the Vermont sheep that were seized by USDA in 2000. As of October 29, 2005, 151 people have died from new variant CJD, far short of the epidemic predicted by the scientific community. Click HERE to learn about alternative theories about the origin of BSE.
Mad cow disease (BSE) and foot-and-mouth disease (FMD) are two distinctly different foreign animal diseases that are capturing international headlines and causing confusion and oftentimes hysteria among the public.
"Mad cow" was identified in Great Britain in 1986 and is believed to have human health implications. Foot-and-mouth is endemic to many countries of the world, but recently broke out in England, where it had not existed since 1967. There are NO human health or food safety concerns with foot-and-mouth disease.
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The
theory that cattle contracted BSE by eating scrapie-infected sheep carcasses
is questionable.
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The United States is known to be FREE from both diseases. Foot-and-mouth (previously, though incorrectly, called hoof-and-mouth) was ERADICATED in 1929. The U.S. does not import livestock, semen, embryos or uncooked meat from any country that is known to have foot-and-mouth disease. Mad cow disease has NEVER been found in the U.S. The U.S. does not import ruminants (cows, sheep or goats), ruminant-derived protein (meat and bone meal) or beef products from any country where mad cow has been diagnosed or from countries whose surveillance and testing efforts are deemed insufficient by USDA.
Foot-and-mouth is an infectious viral disease that affects cloven-hoofed animals such as cows, pigs, sheep, and goats. The first written account of FMD occurred in Italy in 1514. Foot-and-mouth was the first animal disease proven to be caused by a virus. It is characterized by fever and blister-like lesions called vesicles on the tongue, lips, and inside of the mouth; on the teats; and on the tissue around the hooves. In sheep and goats, FMD is usually milder and benign as compared to cattle. Horses are resistant to FMD.
FMD is rarely fatal, but reduces milk production and growth. The impact of a foot-and-mouth outbreak is largely economic – an interruption of commerce, particularly in international markets. Many countries around the world accept FMD as a natural endemic disease, whereas western countries decided some years back to seek disease-free status. A country cannot export livestock or livestock products unless it has FMD-free status.
FMD is the most contagious animal disease known and is easily spread, thus the heightened awareness to travelers, who can unknowingly carry the infective agent on their shoes, clothes, in their nasal passages or in animal products they illegally bring to the United States from infected countries. Mass slaughter of livestock in affected areas of Great Britain is a means of reducing the spread of the disease to unaffected areas. Widespread vaccination is not done because it is difficult to differentiate between animals naturally infected and those that have been vaccinated. More importantly, nations that vaccinate lose their "foot-and-mouth free" status on world markets.
The U.S. government has had regulations in place for years to protect against foreign animal diseases such as foot-and-mouth. We have similar regulations to protect against foreign plant diseases. These regulations are in place 24 hours a day, 7 days a week. The outbreak of foot-and-mouth in the UK and other places merely puts greater emphasis on these regulations, much like a threat of terrorism heightens airport security.
I personally have returned from a country that was experiencing a foot-and-mouth outbreak (Egypt). I checked the appropriate box – that I had been on a farm – on my customs form upon returning and went through the "green" line at airport customs so questions could be asked and appropriate action taken to prevent the spread of any foreign animal disease onto U.S. soil.
The scientific name for "mad cow" disease is Bovine Spongiform Encephalopathy or BSE. It is a member of a family of diseases called Transmissible Spongiform Encephalopathies or TSE's – so named because of the spongy holes that are observed in brain tissue post-mortem. BSE is also a prion disease, because a rogue protein is thought to be the infective agent. In addition to BSE which affects cattle, there are TSE's that affect sheep and goats (scrapie – endemic to the U.S.), mule deer and elk (chronic wasting disease – found in the U.S.), cats, mink (also in the U.S.) and humans. TSE's known to affect humans include: Creutzfeld-Jakob Disease (CJD), Gerstmann-Straussler-Scheinker syndrome, Fatal familial Insomnia, Kuru, and Alpers Syndrome. All are fatal, untreatable diseases that have long incubation periods and affect the central nervous system of the victim. Clinical symptoms include dementia and loss of movement coordination.
While there is still a great deal we do not know about TSE's, until recently, it was believed that each of these diseases was specific to the species that it affected. However, there is some evidence to suggest that BSE may have crossed the species barrier. Approximately 100 people, mostly in Great Britain, have been stricken or died from a new form of Creutzfeld-Jakob Disease (nvCJD), hypothesized to be a human form of BSE or mad cow.
It is not known where BSE came from and or how it spreads, but the original theory placed the blame on sheep scrapie. The theory was that cows contracted BSE when they consumed meat and bone meal derived from scrapie-infected sheep carcasses (a change in rendering practices was thought to have allowed the scrapie agent to survive the rendering process). BSE is believed spread when infected cattle (not yet showing clinical signs of BSE) are themselves rendered into feed and fed back to healthy cows. There may also be some environmental mode of transmission, such as dam to offspring, as is the case in scrapie.
Building on the infected feed theory, humans are believed to contract human-BSE or nvCJD when they consume BSE-contaminated beef products. Since only certain tissues are known to harbor the BSE agent (e.g. brain and spinal cord), these tissues must be consumed directly or come into contact with muscle meat or more likely a processed beef product, such as hamburger or sausage, to cause disease. A recently published study pinpointed out-dated butchery practices in England for allowing "infective" brain tissue to come into contact with other parts of the beef carcass.
There is a feed ban in place in the U.S. which prohibits the feeding of ruminant-derived protein to other ruminants. The McDonalds Corporation is requiring its suppliers to certify that no meat and bone meal has been fed. Purina Mills no longer includes meat and bone meal in its livestock feeds. At the same time, it is important to note that no link between scrapie and BSE has ever been established, and many scientists have dismissed the original scrapie-BSE theory. When cows' brains are injected with scrapie-infected brain tissue, cows develop a scrapie-like disease, not BSE. Moreover, some cows have developed BSE despite never having been fed meat and bone meal. Vegetarians have contracted nvCJD.
Other theories have been put forth as possible causes of BSE and nvCJD, but these theories have not been given the attention nor the funding of the infected feed theory. An organic farmer and independent researcher was the first person to suggest a possible link between organophosphates (pesticides) and BSE. Prior to the BSE outbreak, the U.K. government required farmers to treat their cattle with a pesticide called Phosmet to control the warble fly. The pesticide was applied to cattles' backs at four times the recommended dose. Organophosphates are known to cause TSE-like symptoms. If fact, they are a derivative of the nerve gas the Nazis used during the second world war.
Autoimmune disease and contaminated vaccines have also been suggested as possible causes of BSE and nvCJD. It is known that Louis Pasteur caused neurological disease in human subjects with his first anti-rabies vaccine made from the brain of a rabbit. Midgets injected with human growth hormone developed CJD, as did some women receiving infertility (hormone) treatments, extracted from the human pituitary gland.
The sheep in Vermont that were recently seized by the U.S. government were believed to have been exposed to BSE-infected feed (meat and bone meal) in Europe prior to their entry into the U.S. These sheep had been under constant surveillance by USDA since 1996. Last July, four sheep from one of the Vermont flocks tested "positive" for an undifferentiated TSE. Actually, four tests were performed on the sheep. The first (histopathology) was inconclusive; the second (immunohistochemistry), negative. The third (Western blot) and fourth (capillary electrophoresis) tests were positive, though the latter was experimental and not factored into USDA's decision to destroy the sheep. The test (mouse bioassay) that APHIS is currently using to differentiate between BSE and sheep scrapie (already in the U.S.) takes two to three years before results are known, hence USDA's reluctance to wait for results.
Two of the Vermont flock owners challenged USDA's decision, questioning the validity of the tests, particularly the Western blot test which was done only once and in the absence of negative controls – apparently the tissues were destroyed before this could be done. There is a further question as to why USDA will not use the Prionics test which takes only three to four hours to do and is used to detect BSE in thousands of cattle everyday in Europe.
The chance that these sheep are harboring mad cow disease is extremely remote; however, it is a chance that the U.S. government and livestock industry associations are unwilling to take. The American Sheep Industry Association (ASI) strongly supported USDA's decision to remove the Vermont sheep flocks from their owners.
As stated previously, foot-and-mouth does not pose a human health or food safety risk. It is NOT the same as hand, foot and mouth disease, a viral condition that can affect infants and children. It is safe to eat meat or drink milk from FMD-infected livestock because high temperatures and pasteurization kill the virus. People are an accidental host of FMD and have only rarely been affected. Only about 37 cases of human FMD have been documented in the scientific literature. Symptoms are flu like. Mad cow disease, on the other hand, still presents the scientific community and society at large with more questions than answers.
There can NEVER be a 100% guarantee that the food you eat will not make you sick or even kill you, but according to the Centers for Disease Control (CDC) in Atlanta, if you travel to Great Britain and consume a beef product, your chance of contracting nvCJD is 1 in 10,000,000,000 (one in ten billion). The CDC goes on to say that the risk is "practically nonexistent" in other European countries. BSE has NOT been found in the U.S., thus it is impossible to quantify the risk here. Compare these with the risks you face every time you drive your car, operate machinery, smoke, chew tobacco, don't wear a seat belt or have a hand gun in your house.
*** It is interesting to note that more farmers are committing suicide in Great Britain because of the BSE crisis than people are dying from nvCJD. ***
©
Copyright. 2000. Maryland Small Ruminant Page.