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What Pet Owners-And Other People-Should Know About BSE

Pet Column for the week of January 19, 2004

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Ann Marie Falk
Information Specialist

BSE, which stands for bovine spongiform encephalopathy and has been nicknamed "mad cow disease," has made a lot of headlines since its recent discovery in North America. While the disease is fatal in cattle and there are forms of spongiform encephalopathies in other species, including humans, cats, and deer, BSE poses an extremely low health risk in the United States because of the way it is transmitted.

"This disease was first described in England in 1986. The epidemic peaked in 1993 with 1,000 new cases every week, but is currently expected to be eradicated from Great Britain within 5 years. Most European countries as well as Japan, Israel, and Oman have diagnosed positive cases," explains Dr. Peter Constable, a large animal veterinarian at the University of Illinois Veterinary Teaching Hospital in Urbana.

The current theory is that BSE is caused by a modified infectious protein, called a "prion." BSE prions are found mainly in the brain, spinal cord, and ileum (a segment of the intestines). It is thought that the BSE outbreak in England occurred because brains from infected cows were fed to uninfected cattle as a source of protein.

"Since BSE affects the brain, many of the clinical signs in cattle are neurological. Infected cows have trouble standing and walking. They tend to lose weight, exhibit alterations in their behavior, and may appear frenzied in the late stages of the disease, leading to the nickname 'mad cow disease,' "says Dr. Constable.

There is no effective treatment for BSE. Euthanasia of infected cows is the best option. Unfortunately, there is no way to test live cows for this disease yet. It can be definitively diagnosed only by examining post-mortem samples.

A number of mammalian species has its own form of a transmissible spongiform encephalopathy. In cows it is BSE, in deer it is Chronic Wasting Disease, and in people it is Creutzfeldt-Jakob disease. What is unusual about BSE is that it appears to have crossed the species barrier from cattle into cats (causing about 100 cases of feline spongiform encephalopathy in Great Britain) and also into humans, where the disease is called variant Creutzfeldt-Jacob disease.

"Variant Creutzfeldt-Jakob disease has some similarities, but important differences, to the more commonly occurring Creutzfeldt-Jacob disease. Variant Creutzfeldt-Jakob disease causes neurological problems in people and was first diagnosed in England in 1996. a Like BSE, variant Creutzfeldt-Jacob disease is fatal and there is no treatment. It is widely believed that variant Creutzfeldt-Jakob disease resulted when humans ate BSE contaminated beef," explains Dr. Constable.

Since 1996, only 153 cases of variant Creutzfeldt-Jakob disease have been identified worldwide, with the vast majority of cases in Great Britain. The most infectious tissues of cattlw with BSE-the brain, spinal cord, and ileum-are now removed at slaughter and are not in meat for human consumption. Thus, the chance of contracting this disease is very, very low in North America. The experience in Great Britain would suggest that pigs, horses, sheep, and dogs are resistant to BSE infection, whereas domestic cats are at a very low risk of developing a spongiform encephalopathy.

Commercial pet food poses a very small risk to pets of contracting BSE. Dogs are resistant to the disease. Cats have been diagnosed with Feline spongiform encephalopathy but new evidence suggests this is related to raw meat not pet food. Many pet food companies use chicken as their source of protein not beef. Also in 1989 the FDA increased regulations on what is allowable in pet food to decrease the risk of companion animals being exposed.

In North America the first case of BSE-positive cow was found in Canada in April 2003. On December 23, 2003, BSE was diagnosed in Washington State in a cow originating from a Canadian herd. Officials have tracked down 81 cows in the US from the same Canadian herd. While BSE is not contagious between live cows, there is some concern that these cows may have been infected through a common feed source in Canada.

Steps are being taken to quarantine herds and test additional cows. The USDA's Food Safety and Inspection Service is being extremely cautious. At this point there is no need to avoid beef in the United States. The human health risk has been classified as extremely low.

If you have further questions or concerns about BSE and Creutzfeldt-Jakob disease, please contact your local veterinarian or physician.