1st Invasive Aedes Mosquitoes Found in Contra Costa County

CONTRA COSTA COUNTY, CA — The Contra Costa Mosquito & Vector Control District has identified the invasive mosquito species Aedes aegypti in Contra Costa County. The mosquitoes were found in Martinez, district officials said Friday in a news release.

This is the first group of invasive mosquitoes reported in Contra Costa County.

The district is conducting surveillance and treatment in the area where these mosquitoes were identified with the goal of eliminating them before they become widespread in Contra Costa County; however, they are known to be very difficult to eradicate, district officials said.

"These mosquitoes are very aggressive day-biters that can transmit the causative agents of Zika, Dengue, chikungunya, and yellow fever," said Paula Macedo, general manager of the vector control district.

"They can hide among vegetation and debris which makes them very challenging to find and eliminate," Macedo said. "As we take our responsibility of protecting public health very seriously, we are setting additional traps, and going door-to-door in an effort to find and control these invasive mosquitoes and prevent them from becoming established in the County."

According to district officials, Aedes aegypti are not native to California but can be found around the world in tropical and subtropical areas. They are common in the Southeastern United States and Arizona. More than 10 years ago, they were first discovered in Southern California, and over the years, they have been found in communities from San Diego County north to Shasta County. In 2019, Aedes aegypti were discovered in San Joaquin, Sacramento and Yolo counties.

The invasive mosquitoes are very small —about 1/4 inch —with black bodies and white stripes, the district said. Females can lay individual eggs that can remain dormant for up to six months before being exposed to water, in which they can develop from egg to adult in a week or less. They are often introduced through travel, particularly as people move from area to area and may unknowingly transport these mosquitoes in potted plants or other outdoor items.

To reduce the risk of these new mosquitoes, the district asked Contra Costa County residents to "tip, toss and take action":

• Toss out any amount of standing water.
• These mosquitoes' eggs can stick to surfaces, so after dumping out the water, scrub bird baths, containers, outdoor pet dishes, garden pots for plants, and anything else that can hold water outdoors.
• And report any day-biting mosquitoes by calling 925-685-9301 or online.