CONCORD, CALIFORNIA – The Contra Costa Mosquito and Vector Control District (District) is reporting one chicken from the District’s sentinel chicken flock on Holland Tract, near Knightsen, and two chickens from a flock in Oakley have tested positive for antibodies against West Nile virus.
The District maintains flocks of sentinel chickens at four locations in Contra Costa County. District employees take a small blood sample from each chicken, specifically during the warmest months of the year when West Nile virus is most active. When a chicken is bitten by an infected mosquito, the chicken develops antibodies to fight off the virus. Samples that test positive for antibodies provide evidence of virus activity in specific areas of the county and help the District determine locations for prevention and control efforts.
In addition, one dead bird and one more group of trapped mosquitoes have tested positive for West Nile virus (WNV) in Contra Costa County. The dead bird was collected from Antioch, while the mosquitoes were trapped in Discovery Bay.
There have been 11 dead birds and eight groups of trapped mosquitoes that have tested positive for WNV so far in 2023. The District continues to advise all Contra Costa County residents to take the necessary steps to reduce the risk of mosquitoes and mosquito bites.
“The risk of exposure to West Nile virus will continue until the overnight low temperatures start dropping below 55 degrees. It is important that residents of Contra Costa County continue to take precautions to avoid mosquito bites,'” said the District’s Scientific Program Manager Steve Schutz, Ph.D.
The District recommends residents use an insect repellent that is EPA-registered and includes one of the four most effective active ingredients: DEET, Picaridin, IR3535, or the repellent version of Oil of Lemon Eucalyptus.
In addition to dumping out standing water and scrubbing the inside of the container to remove mosquito eggs, the District also advises Contra Costa County residents to:
- Make sure door and window screens are in good working condition
- Contact the District to request mosquito service
- Report dead birds to the California West Nile Virus Dead Bird Call Center
As Contra Costa County residents take steps to reduce the risk of WNV, District employees will be conducting surveillance and control as needed in the areas where the dead birds and mosquitoes were found.
Contra Costa County residents can report dead birds by phone at (877) WNV-BIRD (968-2473) or online. County residents can also request mosquito service for their residential properties by calling (925) 685-9301 or online.
Since 2005, 75 people in Contra Costa County have been diagnosed with West Nile virus. In 2006, two people died from the disease. For human case information, please visit the California Department of Public Health Vector-Borne Disease Section online.
Contra Costa Mosquito & Vector Control District, an independent special district and public health agency, is located at 155 Mason Circle in Concord.
