The last time Linda Lee checked, there was no imminent threat to the U.S. food and agricultural sector.

But that could change.

“We know that terrorist groups are interested” in using unconventional agents against the food and agricultural sector, she told an audience at the FBI International Symposium on Agriculture on Tuesday.

No one has unleashed a biological agent, such as foot and mouth disease, against the livestock sector. But there have been instances of attacks on the food system. For instance, in 1984, the Rajneeshee religious cult in Oregon spiked the salad bars at several restaurants with Salmonella typhimurium. It sickened 751 people. “The reason they did that was to influence a local election… to sicken enough people so they weren’t able to vote,” said Lee, an intelligence analyst with the FBI.

Targeting the food supply creates fear; it diminishes confidence in the sector that has been attacked, she said.

And, the economic impact of a biological attack on the livestock sector would be huge.

If there is one disease that sends shivers down the spines of livestock producers and security experts alike, it is foot and mouth disease.

“There is no such thing as a small outbreak (of foot and mouth disease). If you have an outbreak, you have a big, big problem on your hands,” Terry Wilson, animal scientist at the University of California-Chico, told those attending the FBI International Symposium on Agroterrorism.

“It’s a billion-dollar disease, period,” he said.

Wilson and Japanese military official Hiroya Goto discussed a food and mouth disease outbreak in Japan in 2010 which cost that country an estimated $3.14 billion. More than 290,000 cows and pigs were culled as a result of the infection.

The Japanese military was part of the country’s response, said Goto, of the military medicine research unit of the Japanese Ground Self-Defense Force.

Goto said a foot and mouth disease outbreak is a national emergency that requires immediate action because it can have a huge impact on the national economy; it can cause massive trade embargoes, and it also has psychological impacts on the public.

And, he said, it needs to be looked at as a potential biological terrorist attack.

To illustrate the disruption it can have on international trade, Taiwan was once a big provider of pork to Japan. Then, in 1997, Taiwan experienced a foot and mouth outbreak. Taiwan's pork exports to Japan went from 266 metric tons of pork in 1996 to zero in 2005.

Earlier this year, South Korea experienced a foot and mouth outbreak.

“There is a lot going on in Southeast Asia with these diseases,” Wilson said. “We want to keep the United States free of them.”

To that end, dairy producers are often referred to as the first-line of defense, keeping their eyes and ears open for any suspicious activity.

Wilson and other experts advise dairy producers to learn the signs of foot and mouth disease and report anything suspicious to a veterinarian as quickly as possible. Veterinarians then need to get laboratory conformation, since the symptoms of food and mouth disease can appear similar to other diseases, such as vesicular stomachitis virus and swine vesicular disease. The blisters that accompany these diseases look similar to one another.