Invasive, disease-spreading Aedes aegypti mosquito found in Santa Cruz County
By Carlos E. Castañeda
An invasive species of mosquito that can carry diseases has been found in Santa Cruz County, authorities announced Monday.
The Santa Cruz County Mosquito & Vector Control District said in a press release that it detected Aedes aegypti mosquitoes near downtown Boulder Creek, the second confirmed sighting in the county following a 2022 identification around the Watsonville area.
Aedes aegypti is an aggressive, day-biting insect about a quarter-inch in size that can transmit diseases such as chikungunya, dengue, yellow fever, and Zika. They have distinctive black and white markings on their legs and upper thorax.
The Vector Control District said staffers have launched expanded surveillance efforts in the downtown Boulder Creek area, with specialized traps that target Aedes aegypti adults, water sampling for mosquito larvae, and door-to-door property inspections. Staffers were able to prevent the spread with similar actions following the 2022 discovery in South County, and the mosquito had not been detected within that area, the district said.
The discovery of Aeges aegypti in Santa Cruz County comes days after officials in Contra Costa County reported additional findings of the mosquito in Antioch, which have been in the area for several months around Holland Tract, an island in the Sacramento-San Joaquin River Delta. The mosquito was also found on the grounds of the Alameda County Fairgrounds in Pleasanton in July and in October 2024. Santa Clara County officials said last year that more Aedes aegypti mosquitoes were being found despite the county’s eradication efforts.
Officials say the species has been found in at least 26 of California’s 58 counties and is established in at least 19 counties, mostly in the Central Valley and Southern California. In 2024, local dengue cases were identified in Los Angeles and San Diego counties.
The district said that residents who develop fever, headache, or joint pain after traveling to areas where dengue, Zika, or chikungunya are active should contact their doctor and stay indoors to prevent possible spread.
Residents are urged to dump out any standing water on their property and to use insect repellents such as DEET, picaridin, or oil of lemon eucalyptus, wear long sleeves and pants, and make sure window and door screens are intact. Residents were also asked to report mosquito bites to Santa Cruz County Mosquito & Vector Control online at mvc.santacruzcountyca.gov via “Submit a Service Request” or by calling (831) 454-2590.
