Chickens Serve as Virus Sentinels


They’re not just chickens, they’re sentinel Chickens.

As West Nile virus creeps westward across the country, California state and local officials are hoping that a flock of 2,000 hens will sound an alarm when infected mosquitoes reach the West Coast.

The 23-year-old sentinel surveillance program, founded by the California Department of Health Services, has been the state’s first line of defense in the fight against St. Louis and Western equine encephalitis, diseases that affect both people and animals. It is operated statewide by districts for controlling vectors--animals, especially insects, that transmit diseases.

Now officials are hoping they’ll be able to use the domestic leghorn hens to detect West Nile virus when it enters the state, and warn the public to take needed precautions before people are infected. It’s up to folks like Susanne Kluh to check up on the birds.


Sitting on a metal folding chair Wednesday morning behind an overflowing recycling bin and construction machinery, she held a plump red hen down by its wings and pricked its comb.

Each time she poked the chicken with the small lance, it kicked its small legs and clucked.

“I’m always too wimpy,” said Kluh, 35, a soft-spoken ecologist with the Greater Los Angeles County Vector Control District.

“I know how they feel. I hate to hurt them,” she said, stroking the chicken to calm it down.

The chickens are placed in outdoor coops, mounted five feet off the ground so hungry mosquitoes can gain access easily. Officials say mosquito species that carry harmful viruses like to feed on birds.

Chickens are ideal candidates to stand “sentinel” because they “don’t get sick and they don’t serve as a source of the virus for mosquitoes to pick up and spread it to other animals,” said Vicki Kramer, chief of the vector-borne disease section of the state health department.


Their bodies create antibodies to fight off the viruses. Officials can tell that infected mosquitoes are in an area if the chickens’ blood tests positive for certain antibodies.

Since earlier this year, officials have been testing for West Nile virus, which has infected 113 people in the United States this year, leading to five deaths.

So far, the virus hasn’t been detected in any Western states, but its arrival appears guaranteed. Jack Hazelrigg, district manager for the Greater L.A. vector control agency, said the virus could show up in California as early as the start of next year.

When it does, the first creatures to be infected will most likely be birds, including the sentinel chickens.

“The mosquitoes here are pretty nasty.” The chickens “get bitten up really good,” said Kluh, who collected samples from the flock caged near the Harbor Park Municipal Golf Course in Wilmington.

“The tule mosquitoes are fierce biters,” she said of Culex erythrothorax, a mosquito species that most commonly carries viruses.


In general, this flock is cooperative. Most of the birds shifted only slightly in Kluh’s lap when the needle pricked their flesh. Even so, the chickens never get used it, she said.

As Kluh dabbed drops of blood onto a strip of filter paper, she whispered calmingly to the chickens. All, she said, have different personalities.

“What’s wrong with you, girl?” she asked softly. “You act like you’ve never done this before.”

There are 200 sentinel chicken flocks in cages throughout California.

While the state oversees the program, 50 of California’s 70 local vector control districts--independent government agencies that operate much like water or sewer districts--maintain the flocks and draw small samples of blood from the chickens every other week.

There are five vector control districts in the Los Angeles metropolitan area. The largest is the Greater Los Angeles County district, based in Santa Fe Springs. It has four flocks, each with 10 chickens.

In most cases, blood samples are shipped to the Bay Area city of Richmond to be tested in labs run by the state health department.


Ted Toppin, a spokesman for the Mosquito and Vector Control Assn. of California, said more than $200,000 is spent each year to purchase and test the chickens. That amount does not include staffing and other related costs.

West Nile virus is a so-called flavivirus commonly found in Africa, West Asia and the Middle East.

It travels via migrating birds and the mosquitoes that prick them for warm blood. The mosquitoes transmit the virus to other birds, people, horses and some other animals.

Most people infected with West Nile have only mild symptoms, such as fever, headache and body aches. But for the elderly and people with compromised immune systems, the virus can be severe, causing encephalitis, a potentially fatal brain inflammation.

Since 1969, California state officials have been testing mosquitoes to detect viruses, Kramer said.

In 1979, state officials began placing flocks of chickens in “strategic locales in California to monitor virus activity,” she said.


In addition to testing caged chickens, Kramer said, the state also examines dead birds, which can be early indicators of viruses like the West Nile.