Like people all over the country, Gary Patronek, a veterinarian who teaches at Tufts University, heard the bizarre story of Ruth Knueven and her 488 cats -- 222 of them dead, and most of the others so wild and sick that they had to be euthanized.

Knueven, 82, charged with five misdemeanors, including animal cruelty, became a public curiosity last week after Fairfax County officials hauled the cats and carcasses out of her home in Mount Vernon and her daughter's townhouse in Burke. Both residences, filthy and damaged, were declared unfit for habitation until repairs are made.

In the Mount Vernon house, authorities said, they found cats squeezed into virtually every open space of the ground floor -- in the furniture, the walls, the masonry.

Unlike a lot of folks, Patronek wasn't surprised to learn how many cats were found in the two homes, either living or reposing in little coffins of Rubbermaid plastic.

"Certainly something in the 500 range would not make me go, 'Oh, my gosh!' " said Patronek, founder of the Hoarding of Animals Research Consortium, a group of eight human behavior and animal experts in the Boston area who have been studying the phenomenon nationwide for the past few years, interviewing dozens of hoarders.

"It's not unusual," Patronek said of Knueven's huge passel of felines. "I mean, it's on the high side. But we've seen cases with over 1,000 animals, cats and dogs together."

Yet it is unusual in the Washington area: Although animal control officials in Maryland, Virginia and the District said they typically deal with a few animal hoarding cases, often involving cats, each year in their jurisdictions, none has encountered a collection nearly as big as Knueven's. She appears to hold the local record -- and by a large margin.

Fairfax police said they plan to ask a judge today to prohibit Knueven from owning pets in the future and also might seek a mental evaluation of her.

"Everybody thinks I'm crazy," said Knueven, who is staying in a motel with her husband. But she said she didn't set out to amass hundreds of cats -- it was just something that happened. She said she took in strays, one after another after another, because she wanted to protect them, and eventually they overwhelmed her. As cats died, she said, she stored them in plastic containers, intending to dispose of them. But she never got around to it.

"It's over now," she said, "and I never want to see another cat in my life."

Patronek, who also is an epidemiologist specializing in animal-related public health issues, said pet hoarding is an old problem. But only in recent years has it come under serious study. His group includes mental health professionals and sociologists from several colleges and officials of the Massachusetts Society for the Prevention of Cruelty to Animals.

Cats are the most commonly hoarded pets, Patronek said, because they are easy to acquire; they are quieter, cleaner and simpler to manage than most dogs; and they interact with humans far more than rabbits, guinea pigs and other small pets do.

Still, he said, "We've seen hoarding of just about every kind of domestic animal you can imagine. You name it. There was a case in Florida where a man had a whole house full of exotic vipers. Birds are not uncommon. Dogs, farm animals, rodents. . . ."

Hoarders themselves also vary.

Although a typical case involves "an older, isolated, economically disadvantaged single woman," Patronek said, "it really could be anyone," not just the classic "cat lady."

"We've had examples of white-collar professionals leading double lives. Even health care providers or veterinarians who are going to work every day, advising people on proper health, then going home to something just like you're seeing" in Fairfax.

Patronek said hoarders are people living with far more animals than they have the space or ability to care for. Knueven's two-story Colonial on Ludgate Drive, bordering George Washington's Mount Vernon plantation, is meticulously groomed on the outside. But like the brick townhouse on Lakepointe Drive occupied by her 57-year-old daughter, the Mount Vernon home was ravaged inside and blanketed with cat feces and urine, authorities said.

Like Knueven, most of the hoarders interviewed by Patronek's group said their motivations were humane -- they wanted to protect the animals. "But we don't think that's really what's going on here," Patronek said.

Without commenting on Knueven, he said: "Ultimately it's not about sheltering or rescuing. . . . The explanation that they're running a sanctuary or shelter is just really disingenuous. They may in their own heads somewhat believe that. But it's really about the animals providing them with something, not vice versa. . . . It's about [the animals] fulfilling a human need they have."

As for what that need is, he said: "We have some ideas, at least. I mean, this is something we're just beginning to scratch the surface of."

After interviewing nearly 50 hoarders, Patronek said, "We're starting to tease out a profile of somebody who probably suffered childhood trauma. They may have had absent parents or unstable parenting. Animals were the only stable fixture in their lives. And perhaps they developed unusually strong bonds with their animals."

In many instances, he said, the obsessions with pets disappeared in early adulthood.

"But ultimately they turn back to animals later in life, and when that return occurs, it's really in a dysfunctional kind of way. And we see the hoarding begin."

Patronek said he wasn't surprised to learn that Knueven kept dozens of her dead felines in clear, plastic containers.

"We think these people have behavioral deficits, which includes avoidance behavior," he said of the hoarders interviewed by the consortium. "They have trouble with responsibility, with making decisions." Some ignored their dead pets. "So you literally walk into a house and you're stepping over carcasses," he said. "But then in other cases, it's not uncommon to see them ritually store the dead animals in some fashion."

He said: "What we think is, they don't want to acknowledge the cat is gone -- because if they did, they might have to acknowledge their role in the death."

In Del Mar, Calif., computer programmer Alison L. Gianotto set up an animal-abuse database after someone tortured and killed her beloved cat. But even with her diligent work, she said, it is difficult to accurately gauge the number of mistreatment cases.

"We'll never know how much of it is going on," she said.

Using information from police, animal rescue groups, court records and other sources, Gianotto lists 4,797 cases of pets being criminally abused in the United States, mostly since 2001. Of those, 343 involved hoarding, including a 2003 case in Caroline County, Md., in which authorities seized 350 cats and dogs. She said 70 of the cats were dead, and the man and woman who owned the property were sentenced to three-month jail terms.

Fairfax officials have charged Knueven with two counts of failing to properly care for pets, one count each of animal cruelty and improperly disposing of a dead animal, and one count of obstructing justice for allegedly interfering with authorities as they tried to gather her cats. She probably would face fines if convicted.

This wasn't Knueven's first brush with Fairfax animal control officials. They seized 120 cats from her in August 2001, although no charges were filed. In two other Fairfax cases recently, authorities said they removed 88 cats from a Falls Church home two weeks ago and took 43 cats out of a house in Lorton on Thursday.

Elsewhere in the Washington area, animal control officials said the few cases they handle annually in their jurisdictions rarely involve more than 30 animals. In Anne Arundel County, though, officials said they seized 86 cats from a Crofton home last year. And Prince William County officials said they took 60 or so cats out of a Dale City house about five years ago.

Michele Hart, an investigator for the Washington Humane Society, said she has dealt with about four cat hoarders in the District in recent years.

"The smell was just overwhelming," she said. "It wasn't 300 cats, thank goodness. But I'm sure they're out there somewhere."

Staff writers Nia-Malika Henderson, Nelson Hernandez, Jennifer Lenhart, Ian Shapira and Jamie Stockwell contributed to this report.

A Fairfax County official posts a sign deeming the home of Ruth Knueven, center, unfit for habitation last week. Officials work at the Burke townhouse of Ruth Knueven's daughter, where 134 dead cats were removed Wednesday.