WASHINGTON — Should foot-and-mouth disease reach this country, the government's emergency response plan lays out a "cascade of events" that would follow, including a halt to all movement of livestock in the state where the case is found. The entire state could later be quarantined.

A positive test for foot-and-mouth "will generate immediate, appropriate local and national measures to eliminate the crisis and minimize the consequences," says a summary of the plan released Friday by the Agriculture Department.

Foot-and-mouth is harmless to humans, but it is dreaded by livestock producers and veterinarians because the virus spreads so easily and quickly. The United States has not had a confirmed case since 1929, although about 100 tests a year are done on animals with possible symptoms of the disease.

"We have been effective up to this point, and I think we'll continue to be effective," said Alfonso Torres, deputy administrator of veterinary services for the department's Animal and Plant Health Inspection Service.

The emergency plan, which has been in existence for years, is still subject to "fine-tuning" as a result of discussions with state and industry officials, Torres said.

Under the plan, a positive test would trigger a "cascade of events . . . starting with a conference call" between state and federal officials.

The state veterinarian would then quarantine the affected farm and consider stopping the movement of animals within the state's borders. State officials would consider destroying the affected herd — a virtual certainty in the case of foot-and-mouth — and determine whether there are wildlife nearby that could spread the disease.

Another series of actions follows when a case of foot-and-mouth is "confirmed positive," meaning that the virus has been isolated and identified after a positive test on an animal.

USDA would quarantine the state to limit the movement of vehicles that could spread the virus to other states.

"The idea of stopping movement immediately so that people and animals and trucks don't move is absolutely critical," said Lonnie King, dean of Michigan State University's veterinary school and a former administrator of the federal inspection service.

"If everything stops moving, then you can catch up with the disease. If not, then the disease is always two or three steps in front of you."

"Movement control zones" would be established around exposed herds, extending at least six miles in each direction. No animals or animal products would be allowed to leave the zones and all people, equipment and vehicles would have to be disinfected before leaving.

Burial, not burning, is listed as the best way to disposing of animals that have to be killed because of exposure to the disease. Burial is easier, quicker and "less polluting," the plan says. Forty-two cubic feet of ground — an area roughly 6 feet by 3 feet by 2 1/2 feet — is needed to bury one cow, five hogs, or five sheep.

A crew of five would be required to kill and dispose of a herd of 40 animals in a day, and another three would be necessary for disinfecting people and equipment on each affected farm.

USDA would secure vaccine to use in containing the disease, if necessary.

Vaccinating herds would be a highly controversial step, as shown in Britain, because it could shut down the country's meat exports. Tests for foot-and-mouth can't distinguish between animals that have been infected with the disease and those that have been vaccinated.

Torres says USDA has sufficient supplies of vaccine available.

The Bush administration, meanwhile, is under pressure from Congress to tighten controls at the nation's borders and airports to keep the virus out. In letters to the Treasury and Agriculture departments on Friday, Sen. Tom Harkin, D-Iowa, said he has "received reports raising serious concerns" about enforcement of restrictions on airline passengers.

Travelers are supposed to disclose whether they have been on a foreign farm while out of the country and declare food products that they are carrying. USDA and Treasury's Customs Service share responsibility for enforcing the restrictions.

On Friday, USDA banned the import of used farm equipment from the European Union and all other countries where foot-and-mouth has been found.

At the White House, spokesman Ari Fleischer said President Bush "is concerned that we make sure the United States does take appropriate action. He's satisfied we have."

On the Net: USDA: www.aphis.usda.gov

U.S. Animal Health Association: www.usaha.org/index.html