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CONCORD, CALIFORNIA - The Contra Costa Mosquito and Vector Control District (District) confirms mosquitoes collected from a trap on Holland Tract this week are the third group of mosquitoes from that location to test positive for West Nile virus (WNV) in Contra Costa County this year.
Please note: These mosquitoes are not the same species that residents of East Contra Costa County have been reporting. The mosquitoes that have tested positive for WNV are from the southeastern part of Holland Tract. The mosquitoes that East County residents have been reporting to the District are coming from the northwestern part of Holland Tract.
“There are 23 native mosquito species in Contra Costa County, which come from different habitats and have different abilities to transmit viruses to people or animals. Only two of the species in Contra Costa County, Culex tarsalis and Culex pipiens, are efficient at transmitting West Nile virus. The mosquito that residents of Eastern Contra Costa County have been noticing is Aedes vexans. This mosquito is an aggressive biter but is not efficient at transmitting West Nile or other viruses to people,” said Steve Schutz, Ph.D., Scientific Programs Manager.
The District is currently working to locate and eliminate the sources of the aggressive mosquitoes in Eastern Contra Costa County.
Because all mosquitoes require water to develop from egg to adult, the most important action Contra Costa County residents can take to reduce the risk of mosquitoes on their own property is to dump out any amount of standing water at least once every week. And if, after dumping out all of the water on the property, County residents are still experiencing mosquito issues, they should contact the District to request mosquito service.
To reduce the risk of mosquito bites from any of Contra Costa County's mosquitoes, the District encourages residents to use EPA-registered insect repellents with one of the following active ingredients:
- DEET
- Picaridin
- The repellent version of Oil of Lemon Eucalyptus
- IR3535
Always follow the instructions on the label when using insect repellent. And report dead birds because dead birds are often the first sign of WNV in a particular location.
Contra Costa County residents can report dead birds online. County residents can also request mosquito service for residential property by calling (925) 685-9301 or online.
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