Recent news reports about the animal disease crisis in Europe and possible threats to U.S. livestock have mentioned both foot-and-mouth disease and BSE (bovine spongiform encephalopathy), also called "mad cow" disease.

Although both diseases pose threats to livestock, they are entirely separate problems with different causes and different impacts.

"Foot-and-mouth disease is a virus and only poses a health threat to cloven-hooved animals -- not to humans, whereas BSE is not a virus but could potentially pose a threat to people," said Patty Scharko, University of Kentucky Extension veterinarian. "Foot-and-mouth disease is by far the biggest immediate concern because if it strikes the U.S. then its economic impact on the livestock industry would be devastating – countries without the disease would probably ban our meat products."

Scharko said it's very important for the public to understand that foot-and-mouth disease and BSE are transmitted in entirely different ways.

"Livestock often get foot-and-mouth by eating infected animal byproducts, but the virus is highly contagious and can travel easily and quickly by a variety of other means such as on farm vehicles, shoes, or even in the lungs of humans who can carry the virus with them and breath it out later at a different location," said Scharko. "BSE, or mad cow disease, is not a virus. We believe it spreads during the intake of infected food and then attacks the brain. In cattle it's known as BSE, but in humans it's called Creutzfeldt-Jakob disease."

Scharko said the U.S. Department of Agriculture has had precautions against BSE in place for several years. A recent case in Vermont where government officials suspected problems in imported sheep instead turned out to be a non-scrapie form of TSE, or transmissible spongiform encephalopathy.

"TSE as scrapie in sheep usually poses no threat to human health," said Scharko, who added that Kentucky vigorously monitors potential disease threats to livestock. "Although we have never seen a case of mad cow disease here in Kentucky, our UK Livestock Disease Diagnostic Center routinely examines the brains of animals that have died from sickness."

According to the USDA, the U.S. has never had a confirmed case of BSE. There has not been an outbreak of foot-and-mouth disease in the U.S. since 1929.