Special Birds Enlisted to Catch Mean Bugs : Public health: Elite flocks of chickens serve as an early warning system for the St. Louis encephalitis virus.

They cluck, lay eggs and scratch for worms just like any other birds.

But the 30 chickens kept by Ventura County environmental health workers are not your everyday brand of fowl.

They’re part of a “sentinel flock,” a feathered force whose mission is to let county environmental health officials know when the mosquito-borne St. Louis encephalitis virus infects local birds.

For seven years, the county has kept chicken flocks in Simi Valley, Thousand Oaks and Fillmore as a kind of early warning system against the virus.

Every two weeks, blood is extracted from the chickens and sent to a state laboratory for analysis.

“We use these chickens like a monitor,” said Randy Smith, who manages the mosquito abatement program for the county. “Hopefully these birds will get infected before any humans.”

Two months ago, the virus was discovered in the Thousand Oaks flock. Then last month, the county had its first human case in Oxnard.

It was the first time the virus had ever been detected in the fowl, and officials say the birds played a vital role in keeping them alert.

On Nov. 30, workers tested the birds for what will probably be the last time this season. Unless the virus is present in one, they will be given away to egg producers and those who want to keep them as pets. The sentinel chickens are part of a statewide program run by the Department of Health Services.

Every year around April, the state officials provide public and environmental health agencies with chickens that have been raised to be free of diseases. The birds are then distributed to counties vulnerable to mosquito-borne diseases. There are about 125 such flocks throughout the state, he said.

Until this year, Ventura County was not considered a hot spot for the virus. That distinction was reserved for the Los Angeles basin, which had 28 cases in 1984, and for Kern County, where the last major outbreak in 1952 infected 800 people.

But the state has kept a special eye on Ventura County since the first human case was reported last month, said Minoo Madon, a public health biologist for the state.

“It’s always significant when a new area is involved,” he said. “The disease is now possible there.”

The early warning program, which has been around for about 10 years, has been effective.

“If this program was not in place, you would have a lot more human cases,” he said. “You would have major outbreaks.”

When the virus is found in a chicken, health agencies issue warnings to the public, and environmental health workers step up mosquito-eradication programs.

The encephalitis virus is only one of two diseases that the flocks are able to detect. Another virus carried by mosquitoes affects mostly horses, but the chickens also contract it.

Madon said the state also wants to keep tabs on the spread of the virus among wild birds such as sparrows, doves and finches.

The county has begun a program to trap wild birds in Oxnard, and probably will put a chicken flock there as well next year.

Smith and another worker recently drew blood out of the chickens one last time before giving them away.

The whole process takes about three minutes. Wearing rubber gloves, Smith carried a chicken from a wooden box and held the struggling bird between his knees as he readied a one-inch hypodermic needle above the jugular.

“Just relax and go easy and we’ll both be out of here,” he told the bird. The bird did, and a minute later, Smith had collected about a tablespoon’s worth of blood.

The blood from all 30 birds was sent to a state laboratory in Berkeley for analysis and no other chickens were infected, Smith said. County workers soon will wrap up the program and begin testing again next year.

With budget cuts under way in other departments, the sentinel flocks represent at least one program that will survive the economic cutbacks the county is imposing this year.

The program cost the county only about $1,500 for laboratory work and $500 worth of grain to feed the birds, said Bob Gallagher, who heads the county’s encephalitis virus program.

“It’s chicken feed,” he said.

Times staff writer Peggy Y. Lee contributed to this article.