First it was SARS. Now, there are concerns about another frightening disease in neighboring Canada: Mad Cow disease. The deadly ailment first appeared in Britain nearly 20 years ago. Here's a closer look at how Mad Cow disease made its way from animals to people.
Mad Cow disease first appeared in Britain in the mid-1980's. The illness, officially known as Bovine Spongiform Encephalopathy or BSE is caused by an abnormal protein that destroys nervous system tissue.
Researchers believe the illness spread to cattle through cow feed made with protein and bone meal from infected animals.
In the mid-90's, scientists discovered that people can get sick by eating infected beef.
More than 100 people, mostly in Britain, have fallen ill or have died from the human form of Mad Cow disease called Variant Creutzfeldt-Jakob disease. Millions of animals were killed trying to contain the outbreak.
The U.S. Dept. of Agriculture says there has never been a case of Mad Cow disease here, and note that a number of firewalls are in place, including banning cattle feed that contains the carcasses of ground up cattle.
Meantime, the USDA has temporarily banned beef imports from Canada as officials investigate the case there.
The Centers for Disease Control and Prevention advises people can reduce their risk of contracting the disease by avoiding beef products when traveling in countries that have indigenous cases of mad cow disease.
The first signs of Mad Cow disease in humans are often psychiatric. Victims may exhibit signs of depression or changes in behavior eventually; symptoms include jerky movements and mental decline.
Canada's first case of mad cow disease was in 1993 in a beef cow imported from Britain in 1987. Since 1990, Canada has not allowed cattle or cattle byproducts from countries with cattle that have had Mad Cow diseases, a Canadian agricultural department spokesman said.