Rabies was discovered in a cat in Potomac two weeks ago, the second known incidence in a domestic animal in Montgomery County since the deadly disease began spreading among raccoons and other wild animals last year. Officials of the county's animal control department say they hope residents will now take the outbreak seriously.

David Wheeler, director of the department, said he was expecting rabies to reach some domestic animals. "There're enough people . . . who don't get their pets vaccinated," he said. "It's the ones that pooh-pooh it who say 'no big deal' that are going to cause the outbreak." Wheeler said that his department, which has taken on six extra staff members, doesn't plan to change its approach in controlling the disease, which has been found in 252 animals in the county in the past seven months.

"We will keep giving the same message, and, hopefully, people will start believing it a little more now," he said. "The message is: Stay away from strange animals, get your pets vaccinated, and keep your animal at home."

The first domestic animal suspected to have contracted rabies recently in the county was a cat that died suddenly Feb. 17. When its owner remembered that his pet had tangled with a raccoon 40 days earlier he asked that the cat be tested for rabies. Although one test proved the cat to be rabid, a sample of the cat's brain tissue has been sent the Centers for Disease Control in Atlanta where it is still being tested for a positive confirmation. The owner was later given a series of six anti-rabies shots.

The most recent rabies case in a pet was discovered after a Potomac family brought a cat to the Montgomery County Humane Society March 19 asking that it be killed, because it was no longer wanted. Family members recalled that the cat had had an encounter with a raccoon a few months previously.

While the cat had not shown signs of rabies infection, the Humane Society "immediately euthanized the animal and sent it to the laboratory, where they discovered it had rabies," said Sharon Kessler, assistant director. Family members have started the series of anti-rabies innoculations.

The disease has recently been found in Montgomery mainly in raccoons. It is also known to have been contracted by four skunks, a beaver and the two cats.

The outbreak began in Montgomery last September, when three cases of rabies were reported. By December, 66 cases had been recorded in Montgomery. Rabies had spread to 135 animals by Feb. 15; 216 animals by March 15; and 252 animals as of April 1, animal control officials said.

Since the beginning of 1983, 266 cases of rabies have been found throughout Maryland, including 185 in Montgomery County, 37 in Frederick County, 30 in Washington County, 10 in Allegany County, two in Prince George's County (both raccoons), one in Baltimore County, and one in Garrett County.

Health officials in West Virginia were alarmed recently when a cow died of rabies. They say it is an indication that the outbreak may be worse than they originally thought.

Montgomery County health officials say 32,200 dogs and cats have been vaccinated, less than half the estimated number of such animals in the county.

Rabies is a virus that affects the central nervous system and is transmitted through the saliva of its carriers. No warm-blooded animal is naturally immune to the disease, but it is rarely found in humans, rodents, squirrels, possums and rabbits. It is most common in bats, skunks, raccoons and foxes.

Wheeler said his department has tested 1,800 animals since September--"literally every raccoon we've picked up, including dead ones on the road."

The only way to determine if an animal has rabies is to kill it and stain a portion of brain tissue. If rabies is present a florescence will show up in the stain.

People who suspect an animal is rabid should call the Montgomery animal shelter at 279-7560, or the Prince George's County animal shelter at 336-3221. Do not try to trap the animal yourself--a staff member will be sent out to catch it.