Bird-Watching a Deadly Virus : Groups of Chickens Tested for Signs of Mosquito-Borne Disease

Nasr Gergis pulled one of nine clucking, scurrying white Leghorn chickens from a wire-and-wood coop tucked away in a corner of Irwindale’s Santa Fe Dam Recreation Area. Then, holding the chicken tightly to prevent any squirming, Gergis stuck a needle into its neck and drew blood into a syringe.

One by one, Gergis, an environmental specialist for the county health department, caught each chicken and drew a sample as his partner, Gail Van Norton, numbered the vials with the chickens’ identification numbers. It was their twice-a-month call on Los Angeles County’s “sentinel” chickens.

Somewhat like canaries that alerted coal miners to danger, 15 flocks of sentinel chickens--including five flocks in the San Gabriel Valley--serve as an early warning system in the detection of a potentially deadly virus carried by mosquitoes.

And these days the chickens--via their blood--are sending out a message: Trouble could be brewing with mosquitoes this summer.

From coops in Pomona to Monterey Park, Wilmington, Los Angeles and Irwindale, tests earlier this month indicated the presence of mosquitoes that were carrying the virus, known as St. Louis encephalitis.

It causes flu-like symptoms in humans and, at its worst, can damage the brain and spinal cord, resulting in tremors, paralysis, coma and death. Babies and the elderly are particularly vulnerable.

In the case of birds, however, usually only the fledglings are adversely affected. Adult birds, both wild and domestic--have built up sufficient antibodies to ward off problems. Still, birds can serve as what is known as “reservoir hosts” for the virus.

The disease gets spread when certain varieties of female mosquitoes look for a meal. First, the bugs bite birds, getting the virus along with the nourishment. With the next bite, they can pass it on to a human.

Although the semi-desert of Southern California is by no means as mosquito-prone as muggy places like Mississippi, Louisiana or the Everglades--where health officials battle mosquitoes by spraying insecticides from aircraft--conditions here can combine to create mosquito problems.

Swimming pools, buckets, fountains and construction sites all can be mosquito breeding spots in Southern California. And one of the most frequent breeding grounds is floral vases in cemeteries.

High numbers of mosquitoes in recent weeks have prompted warnings from the health department for the public to be aware of mosquitoes, to guard against their bites by using repellents and wearing loose-fitting clothes and to eliminate breeding locations.

A network of governmental agencies, including “mosquito abatement districts” in the county and throughout the state, link forces to fight St. Louis encephalitis, one of several versions of encephalitis viruses and the most common in this region.

The mosquito districts, which apply insecticides to stagnant pools of water, work closely with the county and state health departments in running the chicken-testing programs.

“We’re very proactive,” said Frank Hall, chief of county health department programs that oversees a number of the chicken flocks. “Our standard is to not allow any human cases to occur.”

Until recently, the virus was confined to rural areas of the state. Then in 1983 came the first confirmed case in Los Angeles County. The following year was the county’s worst season to date: 16 cases, including a Long Beach woman in her early 60s who died. There were also five cases in Orange County, four in Riverside County and one in San Diego County.

A total of four more cases were recorded in 1985 and 1986.

Then in 1989 in the Antelope Valley, a 65-year-old Quartz Hill man was hospitalized with the virus for three weeks.

And last year, a 39-year-old man from Valinda, an unincorporated area of the central San Gabriel Valley, went into a seizure and was hospitalized for more than two weeks. He still suffers from effects of the disease, which he probably contracted from mosquito bites at the Santa Fe Dam.

So far this year there have been no reported cases. But Kenn Fujioka, an epidemiologist with the county health department’s acute communicable disease office, said: “For every one severe case of St. Louis encephalitis in Los Angeles County, there are probably 100 people who don’t require hospitalization and don’t even know they have it.”

The symptoms may be nothing more serious, he said, than a stiff neck and a three-day fever.

When compared to the risk of contracting many other diseases that occur with greater frequency, the chances of getting St. Louis encephalitis can be kept slim by suppressing the mosquito population, health officials said.

“The lower the number of mosquitoes you have, the less the chances are of you getting the disease,” Hall said. “But theoretically you can have one mosquito that picks up the virus from a bird and then you can be the unlucky one that gets bitten and gets the disease.”

The reason to take such elaborate steps as maintaining flocks of chickens and testing them regularly is that in the megalopolis of Southern California an epidemic could be devastating, Fujioka said.

“That’s why we go to such lengths,” said Fujioka. “An apparent rare disease can become a rather explosive one fairly quickly.”

That happened in 1933 in the case of St. Louis, the city from which the virus gets its name. There were 1,350 cases in St. Louis and nearby Kansas City, St. Joseph and Louisville, Ky. Two hundred and sixty-six people died.

Today, Fujioka said, “even one death from St. Louis encephalitis is needless.”

When health officials get positive readings from the sentinel chickens, they intensify local efforts in the vicinity of the flock to find and eliminate mosquito breeding grounds.

The sentinel chicken flocks, established locally in 1984, are one half of the research and testing phase. County health officials such as Gergis and Van Norton also trap mosquitoes to determine if they are carrying the virus.

To attract the insects, Gergis, who trained as a veterinarian in his native Egypt, and Van Norton, a mosquito expert, use mesh-net traps with a small light and little chunks of dry ice, which in their release of carbon dioxide mirror the exhalations of humans.

The results from the mosquito tests combined with the chicken research give solid indications of where the virus may likely be a danger to humans.

“We still don’t know a lot about the hows and the whys the virus is transmitted to Los Angeles County,” Van Norton said. But she said that, besides using the chickens, researchers have started to test such wild birds as sparrows and finches.

“A while back,” said Van Norton, “we even had a case of a pigeon in downtown L.A. that tested positive for encephalitis.”

In the case of the Valinda man who was bitten last year in Irwindale, the sentinel chickens had already given a clear indication of danger and the health department had issued its standard warnings in the San Gabriel Valley. At the time, the flock was larger with 15 chickens. Fourteen tested positive.

Now, the virus has come back again--one of the nine chickens at Santa Fe Dam has tested positive.

“It’s still pretty early in the season,” Fujioka said. “But just because we haven’t seen any cases yet doesn’t mean they won’t occur.”