Federal and Virginia wildlife officials began killing 250 to 300 domesticated ducks yesterday on Lake Braddock and a small nearby pond in suburban Burke to prevent the spread of a highly contagious disease that has already resulted in the deaths of several dozen Muscovy ducks.

"I hope people understand that this was done with reluctance on our part," said Donald V. Pafford, executive director of the Lake Braddock Community Association, which represents 1,297 families. "We had no choice but to control this disease."

The community association's board of directors voted Wednesday evening to go along with the recommended program, which includes eliminating the ducks by feeding them corn laced with enough tranquilizers to kill them, then incinerating the carcasses and disinfecting the lake, pond and shoreline.

Pafford said he was concerned that some residents might try to protect individual ducks from their deaths by feeding them so they wouldn't have an appetite for the corn.

"If we don't kill these ducks, we will never have any more ducks at Lake Braddock," he said. "We have to do this to kill the virus. There isn't any other way."

The ducks began dying in June. Some neighbors questioned whether a herbicide sprayed on poison ivy around the pond might be responsible. But the problem was later traced to a relatively uncommon disease known as duck plague, or duck virus enteritis.

The disease is caused by a herpes virus that made its first appearance in this country in 1967 in the Long Island commercial duck industry, said Milton Friend, director of the National Wildlife Health Center in Madison, Wis.

There is no vaccination against it, Friend said, and no known cure. It affects ducks, swans and geese, but not humans, songbirds or other animals.

"It has been increasing, especially on the Atlantic Coast," he said. "I can't give the exact figure, but we've probably had in the last 12 months maybe eight or 10 episodes of this, all in the same kind of non-wild situation we're seeing here."

The virus is transmitted to other waterfowl through droppings and bodily discharges. A bird may harbor the disease for a long time, Friend said, before it begins to show the advanced symptoms of massive tissue destruction and heavy internal bleeding.

Friend said his biggest fear, and that of other wildlife specialists, is that the disease will become established in wild duck, goose and swan populations.

The only time duck plague has significantly affected a wild bird population was in the Lake Andes National Wildlife Refuge in South Dakota in 1973, when it was deemed responsible for the deaths of more than 40,000 wintering mallards, Friend said.

Of the Lake Braddock and Braddock Pond elimination program, he said: "It's one of those things. It's unfortunate whenever you have to destroy animals, especially to us, but you have to look at the good of the entire population."

By noon yesterday, only eight ducks still swam around Braddock Pond. The remaining birds are expected to be dead within a day or two, said Pafford.

Afterwards, he said, the one-acre Braddock Pond would be treated with soda ash to raise the alkaline level enough to kill the virus.

Then, the pond will have to be drained and treated again with soda ash or lime. He expected it would have to remain empty until at least next summer.

The 28-acre Lake Braddock is too big to drain, but its water level will be lowered by as much as six feet, and the exposed areas will be treated with a disinfectant guaranteed not to kill fish.

Pafford said it may be necessary to erect fluttering banners, or employ some other method of discouraging wild ducks from using the pond and lake until the virus has been eradicated.

He added that he hoped the community would once again have its own flock of ducks, but that it wouldn't happen at least until next spring. Even so, the first returning ducks will have to be carefully monitored for signs of the disease.