August 30, 2004
With Maricopa County’s West Nile virus outbreak in full swing, public health authorities expected that all seven of their chicken flocks, used to signal the spread of the virus, would have tested positive many weeks ago.
But one flock, located in Queen Creek, beat the odds until Aug. 19.
The birds, which can get West Nile without succumbing to it, are used by the Maricopa County Environmental Services Department as warnings of the virus when it first appears in different areas of the community.
Called sentinel chicken flocks, they function as guards over public health.
But in Queen Creek, where public health officials said mosquitoes, horses and humans have tested positive for West Nile, the county’s sentinel chicken flock had escaped infection by the mosquito-borne virus nearly four months into the West Nile season.
"That was a surprise for us," said Al Brown, director of the county’s Environmental Services Department. "We thought that that was unusual (considering) that we’ve had all these positive indicators in the Queen Creek area."
Mosquito control authorities suspect that the flock’s location away from flood irrigation and closer to a desert area in Queen Creek may have spared the chickens as the West Nile outbreak picked up speed.
Although the chickens failed to work as warning signs in Queen Creek, the county uses other indicators to track the outbreak, said John Townsend, the county’s vector control manager.
Birds that may have died from the virus are brought in by residents for testing, and mosquitoes, the most timely indicator of the virus’ location, are trapped and tested all season long.
Unlike chickens and other birds, which don’t turn positive for antibodies to West Nile until about two weeks after a bite, mosquitoes show the virus shortly after biting an infected bird.
Still, sentinel chicken flocks are an important tool in tracking vector-borne diseases such as West Nile, and will be used again next year, Townsend said.
The flocks are left with individuals who agree to have them on their property, where the chickens are tested once or twice a month for diseases including St. Louis encephalitis, western equine encephalomyelitis and the West Nile virus. In return, the property owners can keep the chickens’ eggs.
"What we’ll probably do is move it next year," Townsend said of the Queen Creek flock.
Meanwhile, ground-level pesticide fogging for mosquitoes continues in Queen Creek. Portions of Queen Creek in Pinal County were to be fogged from midnight Sunday to 5 a.m. today, said Pinal County spokesman Joe Pyritz.