On The Farm: Mad cow disease can be prevented
Updated 8:15 AM on Sunday, July 30, 2006
By ERIC ZIMMERMAN
Special to the Eagle
As discussed in recent weeks, the United States is seriously threatened by potential occurrences of foreign animal diseases. Based on epidemiological studies, the state and federal animal health regulatory agencies have developed safeguards to prevent the entry of these diseases into the United States. Education is the key to identifying the unusual symptoms of these diseases so that, should they occur, they can be detected and reported rapidly. Regulatory agencies are prepared and ready to respond should an animal disease outbreak occur, whether accidental, natural or intentional.
Bovine spongiform encephalopathy (BSE), also referred to as mad cow disease," affects the central nervous system of cattle. It was named for the spongy appearance of the affected brain tissue. The causative agent is an abnormal form of the prior protein of the central nervous system.
BSE was first diagnosed in Britain in 1986 and has since infected more than 178,000 head of cattle. Only two animals have tested positive for BSE in the U.S. to date - the first animal was originally from Canada, and the second animal was grown in Texas. The United States is still classifying BSE as a foreign animal disease rather than an emerging disease.
Transmission
Cattle can become infected with the disease by eating contaminated food. Since the disease peaked in 1993 in Britain, governments have banned certain foodstuffs from animal feeds. These foodstuffs are meat, blood and bone meals, brain, spinal cord, skull, vertebrae and ileum.
Since the implementation of the ban, the occurrence of BSE has decreased. Once an animal has become infected with BSE, the incubation period is two to eight years. During that time, the animal will appear normal and have no obvious clinical symptoms. However, once symptoms appear, the animal's condition quickly deteriorates, and it dies within two weeks to six months. Animals that contract BSE live an average of three to six years.
Diagnosis
There are several different symptoms associated with BSE including:
ï change in temperament such as nervousness or aggression
ï abnormal posture
ï lack of coordination
ï difficulty rising
ï decreased milk production
ï loss of body weight despite continuous appetite
There is no way to test for BSE in live cattle. The only way to diagnose the disease is to do a postmortem inspection of brain tissue to locate the abnormal form of the prior protein. BSE is a terminal disease with no treatment and no vaccine.
Prevention, regulation
The USDA Animal and Plant Health Inspection Service works to prevent BSE in the U.S. and responds when a possible case is reported. APHIS bans the import of ruminants and ruminant products (such as fetal bovine serum, bone meal, meat, blood meal, offal, fats and glands) from countries where BSE occurs. APHIS also has prohibited the use of mammalian protein in cattle feed.
As part of the USDA surveillance program, the Food Safety and Inspection Service inspects all cattle before they are slaughtered and maintains an interlocking system of safeguards designed to prevent BSE from entering the human and animal food chain. If an animal is down and unable to rise or exhibits any central nervous system problems, it is pulled from the slaughter group, its place of origin is identified and the animal's brain is sent to the National Veterinary Service's Laboratory in Ames, Iowa, for testing to determine whether the animal is infected with BSE.
Animals pulled for testing never make it into the food chain.
ï Eric Zimmerman is a Texas Cooperative Extension agent in Brazos County specializing in agriculture and natural resources.
