WITH U.S. FORCES, SAUDI ARABIA -- Military authorities have notified U.S. forces in Operation Desert Shield that they intend to vaccinate American troops against an Iraqi biological warfare attack using anthrax bacteria, but there is no vaccine currently available in Saudi Arabia, a Navy expert said today.

Cmdr. Thad Zajdowicz, chief of infectious diseases at the Navy's Fleet Hospital Five here, described anthrax as an animal disease transmittable to humans, with a mortality rate that can reach 90 percent if the bacterial spores are inhaled in massive doses. There is no record of anthrax tranmission between humans.

A reliable vaccine exists, Zajdowicz said, and could be administered "in a matter of weeks" to the 300,000 U.S. troops currently deployed in the Persian Gulf area "through the established health care system."

"We've gotten message traffic on this," Zajdowicz said. "But there are no stocks {of vaccine} in the country."

The Defense Department in a statement last week confirmed that Desert Shield soldiers would soon be vaccinated against unnamed germ-warfare agents to offset a possible biological warfare attack by Iraqi troops arrayed against them.

Iraqi President Saddam Hussein is known to have ordered the use of chemical agents, including nerve gas and blister gas, against Iranian troops in the Iran-Iraq war and against Kurdish rebels in his own country.

But while Iraq was believed to be experimenting with germ warfare, it was not until two months ago that CIA director William H. Webster said in a speech that Saddam's forces had biological agents. House Armed Services Committee Chairman Les Aspin (D-Wis.) later said intelligence analysts believed that Iraq would be able to use germ warfare after Jan. 1.

Desert Shield forces have established an elaborate system of detection, prevention and treatment for chemical agents, but have not emphasized defense against biological warfare because of technological difficulties in developing and delivering such weapons.

One expert expressed doubt that Iraq would use germ warfare, but noted that the threat alone could serve Saddam as an effective psychological tool. U.S. forces through training have largely demythologized chemical warfare, but the possible use of biological agents has added fresh concern.

Germ warfare envisions the spread of infectious disease by delivering bacterial spores in projectiles or as an aerosol spray carried by the wind. The winter months offer the best climatic conditions for the spread of biological agents in the Arabian Desert because the prevailing winds move in a southerly direction -- from Iraq to Saudi Arabia.

Independent experts have mentioned anthrax as only one of several diseases potentially transmittable in this fashion. Others include cholera, typhoid fever, botulism and tularemia.

But, said Zajdowicz, "the agent that is of concern is anthrax." He said researchers know more about spreading anthrax and about the effects of the disease when used as a weapon. Large doses, he said, can produce symptoms in 12 to 24 hours, making them useful as a tactical weapon. The other agents either have a longer incubation period or would disperse too quickly to be harmful.

However, many experts in the United States, including Webster, said anthrax is not of value as a tactical weapon because of the incubation time.

Zajdowicz said U.S. authorities record a few cases of anthrax every year, usually among people who work closely with ruminant farm animals like cattle, goats and sheep. Vaccination is confined to farm workers, veterinarians, researchers and others who work with animals.

"Anthrax has never been a standard immunization, because it's not adjudged to be a threat," Zajdowicz said. "Obviously the betting odds on that have been changed because of our current adversary."

Humans contract anthrax either through the skin or by inhaling the spores, he said. The surface boils are easily treatable, he said, but pulmonary anthrax "is a rather nasty disease" that affects the area between the lungs and heart. Symptoms include pneumonia, chest infection and chest pain. Death comes from internal bleeding.

Zajdowicz said anthrax can be treated with antibiotics with some success. Other experts said penicillin can combat the symptoms and can also be used in lieu of vaccine as partial protection from contracting the disease.

Zajdowicz noted that while the standard chemical warfare gas mask will protect humans from anthrax, full immunization is achieved only through a series of injections. Still, he added, "you get some protection with as little as one shot."

"The most formidable task is to get vaccine and get it out to the troops," Zajdowicz said.