Bovine spongiform encephalopathy
Bovine spongiform encephalopathy (more commonly BSE or mad cow disease) is a fatal neurodegenerative disease of cattle, part of the transmissible spongiform encephalopathy family of diseases. BSE is believed to be caused by prions and to have evolved from the sheep prion disease scrapie through the use of sheep protein in animal feed for cattle. One type of human prion disease, Creutzfeldt-Jakob disease, is thought to be transmitted to humans through the ingestion of beef contaminated with BSE. Another related prion based disease found in deer and elk is Chronic Wasting Disease (CWD).
Eating meat from cattle with BSE is thought to have caused the new variant of Creutzfeldt-Jakob disease (nvCJD) in about 131 cases (2003 June data) in the United Kingdom and some few in France. Rodents injected with brain tissue obtained from cows with BSE develop a fatal neurological disorder in one or two years.
It is possible to detect the abnormal prion protein in some, but not all, of these animals' brain tissues. Although there is substantial evidence for transmission of the disease by prions, and various theories have developed about the absorption of prion proteins by intestinal cells, there is still no definite proof reliably showing that eating infected beef is really the cause of the new variant Creutzfeldt-Jakob disease.
There is also some concern about those who work with (and therefore inhale) cattle meat and bone meal, such as horticulturalists who use it as fertilizer. The first BSE epidemic was recognized in the United Kingdom in 1986.
BSE is thought to have spread by the practice of feeding cattle a diet which included meat and bone meal, a high-protein substance obtained from the remnants of butchered animals. This practice allowed the accumulation of prions over many generations.
The use of meat and bone meal as a protein supplement in cattle feed was widespread in Europe prior to about 1987. Soybean meal is the primary plant-based protein supplement fed to cattle, and soybeans do not grow well in Europe. This means high costs, and cattlemen throughout Europe turned to the less expensive animal byproduct feeds as an alternative.
Soybean meal is cheap and plentiful in the United States. As a result, the use of animal byproduct feeds was never as common as it was in Europe. U.S. federal regulations have partially prohibited the use of animal byproducts in feed for ruminants since June 1997. Ruminant animals, such as cattle, sheep and goats, are not allowed to be fed back to other ruminants. Pigs, chickens, pets, deer, and other animals, however, still can eat ruminant slaughterhouse waste as well as the animal byproducts of their own species. Ruminants also can still be fed non-ruminant waste under the rules. [1] In February 2001, the United States General Accounting Office released a report that said the United States Food and Drug Administration, which is in charge of regulating animal feed, has not adequately policed the feeding ban. [2] The USDA now estimates that, should BSE occur in a U.S. cattle herd, it would die out of its own accord rather than spreading, due to these restrictions.
At least three cases of BSE have occurred in North America, with one occuring in the United States on December 23, 2003. No case of new-variant Creutzfeldt-Jakob disease has occurred in North America so far, except among those who have travelled to Europe.
A case of BSE was reported in Canada on May 20, 2003. It occurred in a single older cow that may have contracted the disease from contaminated feed in earlier years. The animal had been destroyed and declared unfit for consumption prior to being diagnosed. The United States issued a temporary ban on all Canadian beef. The last North American case of BSE was in 1993, involving an animal born in Britain.
On September 26, 2003, it was reported that an experimental treatment given to a Northern Irish teenager halted the progress of brain damage caused by variant Creutzfeldt-Jakob Disease (vCJD). The drug, called pentosan polysulphate and commonly used to treat cystitis, was injected into the patient's brain. The patient's weight and heart rate returned to normal levels after receiving the treatment. Still, there is no cure for vCJD, a fatal disease. [3]
On December 23, 2003, the first case of BSE in the United States was found in a single Holstein cow in Washington State. Agriculture Secretary Ann Veneman said a sample taken on December 9 was tested twice and came back as a "presumptive positive." Ms. Veneman said that 20,526 cows had been tested in 2003, and that this discovery was "a clear indication that our surveillance and detection program is working."
Shortly after the discovery of BSE in the United States, Japan and South Korea instituted temporary bans on US beef imports, until more information about the US BSE outbreak becomes available. Japan and South Korea and the number 1 and number 3 importers of US beef in the world. The economic impact of their bans on beef imports from the US will be critical for all involved, it is hoped that the beef crisis can be resolved quickly so trading can begin again. [4]