Plague Detected in Squirrels : Blood Tests on Animals Captured in Agoura Park Are Positive

Blood samples taken from three ground squirrels captured in an Agoura park have tested positive for bubonic plague, county health officials said Thursday.

The test results are the first sign of plague this year in Los Angeles County, said Frank Hall, director of the county Department of Health Services’ plague surveillance unit, which took the samples as part of its continuing effort to monitor the rare but potentially deadly disease.

Hall said the samples were collected in Vasa Park, on Triunfo Canyon Road, in June, but county officials only this month learned the results of the tests, which were conducted at a federal laboratory in Colorado.

Plague shows up periodically in rodents in hilly areas around Los Angeles, usually in ground squirrels, Hall said. The disease is caused by a bacterium that is transmitted from animal to animal, and sometimes to man, by fleas.

Appears in Late Summer

“It’s strange, this bacteria,” Hall said. “We know it’s there, but it lies dormant, then pops up in a population, then lies dormant again. It usually starts to appear in late summer. We’ve only just begun,” he said.

The county regularly checks rodent populations at about 400 sites around Los Angeles County, taking blood and flea samples and looking for changes in animal populations that might signal a “die-off.”

Signs of the animal “die-off” include dead ground squirrels or rats, or empty burrows--often noticeable because their entrances become covered with cobwebs.

Posters warning visitors to avoid contact with wild animals were placed in Vasa Park, a privately owned picnic ground, the day after officials learned of the positive tests, Hall said.

2-Stage Eradication

Along with the county agricultural commissioner’s office, the health department has begun a two-stage procedure to reduce the park’s population of ground squirrels and their fleas.

The park area, especially the squirrel burrows, was dusted with Sevin, an insecticide, said Richard Wightman, supervising agricultural inspector for the county. Officials also set out boxlike dusting stations, which spray insecticide onto squirrels after they are attracted by bait.

The fleas must be attacked before the squirrel population is cut, Wightman said. “You don’t want to kill the host first because then you’ve got fleas out looking for warm bodies. And those warm bodies could be kids,” he said.

He said county agriculture personnel will begin placing poison in the park to reduce the squirrel population next week.

More rodent blood samples have been taken from squirrels trapped in the park and at a nearby day camp since the county learned of the test results, Hall said. Health inspectors also asked residents living near the park to have their pets tested. So far, blood samples have been taken from two dogs and two cats, Hall said.

Results have not come back on the recent tests, Hall said.

The blood samples are sent to a laboratory in Fort Collins, Colo., run by the plague branch of the federal Centers for Disease Control. The lab tests thousands of samples a year sent from 11 states, according to Allan Barnes, director of the plague branch.

The last cases of plague in people in the Los Angeles area were reported in 1984, involving a Claremont veterinarian and a Bradbury woman who was bitten by an infected flea while camping.

There have been six human cases of plague in the United States this year, one in Northern California, one in Arizona and four in New Mexico, Barnes said.

Even though the disease only rarely strikes humans, surveillance efforts are important because plague always has the potential to cause an epidemic, Barnes said.