Mosquitoes Are the Deadliest Animals on the Planet. That’s Why the District is Working Hard to Control a Particularly Dangerous Mosquito in Contra Costa County
How Did Mosquitoes Get So Dangerous?
Females of most mosquito species feed on the blood of people or animals, therefore, they are capable of transmitting parasites and viruses that cause diseases, including malaria, dengue fever, and West Nile virus, from one host to another. These diseases are responsible for up to one million human deaths each year, worldwide.
Only female mosquitoes bite humans and animals, because they need extra protein from blood to produce eggs. Male mosquitoes are not capable of biting humans or animals, and feed only on plant nectar and other sugar sources.
How Did Mosquitoes Get So Dangerous?
Females of most mosquito species feed on the blood of people or animals, therefore, they are capable of transmitting parasites and viruses that cause diseases, including malaria, dengue fever, and West Nile virus, from one host to another. These diseases are responsible for up to one million human deaths each year, worldwide.
Only female mosquitoes bite humans and animals, because they need extra protein from blood to produce eggs. Male mosquitoes are not capable of biting humans or animals, and feed only on plant nectar and other sugar sources.
A male Aedes aegypti mosquito
What Makes Aedes aegypti so Dangerous?
This is not the mosquito you see on your arm and swat. Aedes aegypti is a small, daytime-biting mosquito that hides in vegetation and is difficult to spot. The females typically bite people below the knees during the daytime. They feed on people quickly and efficiently, and most people don’t notice the bite until the mosquito is gone. They’re particularly dangerous because they can transmit the viruses that can cause Zika, dengue fever, yellow fever, and chikungunya from person to person.
These mosquitoes are invasive and not native to California, yet they have spread across the state since they first arrived in Southern California 15 years ago. They’ve spread in part because they lay individual sticky eggs just above the water line of backyard containers like potted plants, pet bowls, and other backyard containers, including toys and large tools.
Those eggs may not be noticed when people pack up their plants and other containers and move from city to city. Once they water the plants, the eggs begin to grow into adult mosquitoes, potentially introducing these dangerous mosquitoes to new areas.
The Contra Costa Mosquito and Vector Control District (District) found Aedes aegypti for the first time in Martinez in 2022. Fortunately, the area where these mosquitoes were detected was small, and District employees worked with residents to control the mosquitoes. The District’s laboratory staff continues to set mosquito traps in that area, but no more Aedes aegypti have been found in Martinez.
In late 2024; however, the District detected Aedes aegypti in Antioch, and the District’s laboratory staff have found them in Antioch each year since, including this year.
What is the District Doing to Control Aedes aegypti in Antioch?
District employees have been going door to door in the areas where these mosquitoes have been found to check every front and back yard for anything holding water and any evidence of Aedes aegypti in an effort to control them. The District has also conducted larval mosquito control by truck, targeting the young mosquitoes as they grow in the water, similar to the products you can buy in your garden store. The District is also looking at some innovative ways to control this mosquito.
What Other Districts are Doing to Control Aedes aegypti
In Southern California, where the invasive mosquitoes were first detected in the state, Mosquito and Vector Control Districts have turned to a practice that has been around since the 1950s, when scientists first used Sterile Insect Technique (SIT) to fight the invasive screwworm fly, which is a serious parasite infecting cattle. SIT involves releasing sterile male insects to mate with female insects, resulting in non-viable offspring. This process was also used in the 1990s to stop the Medfly in Southern California. Today, SIT is also known as Innovative Mosquito Reduction or IMR.
Some Southern California Districts are using a process called Irradiation to control Aedes aegypti. This process places male Aedes aegypti mosquitoes through an X-Ray machine to sterilize them. The males are released to mate with the female Aedes aegypti, which are unable to produce eggs that survive.
Another type of Innovative Mosquito Reduction technique uses natural bacteria called Wolbachia. These bacteria exist naturally in many mosquitoes and other insects, such as butterflies, fruit flies, dragonflies, moths, bees, and beetles. When male Aedes aegypti are treated with a particular strain of these bacteria and then released into the wild to mate with female Aedes aegypti, the females, which carry a different strain, produce eggs that fail to hatch.
The Wolbachia bacteria that are used are specific to insects and do not affect humans or pets.
Since males are not capable of biting or transmitting diseases, both of these processes reduce the population of these dangerous mosquitoes over time, without impacting humans.
Photo by Contra Costa Mosquito & Vector Control District
What Can Residents Do to Reduce the Risk of Aedes aegypti?
The most important thing Contra Costa County residents can do is dump out any amount of standing water on your property at least once every week because mosquitoes require water to grow from egg to adult. By dumping out the water, you deny mosquitoes a place to grow, reducing or eliminating the population.
Contact the District If You Experience Daytime Biting Mosquitoes
If you are outside during the daytime and find yourself scratching a mosquito bite on your leg or ankle, contact the District. Aedes aegypti mosquitoes are very quick and can bite a person and fly away before you even know you have been bitten.
Contra Costa County residents already pay for District services through property taxes and benefit assessments, so there’s no additional charge for any of our residential services. So use us when you need us.
Contra Costa Mosquito and Vector Control District, an independent special district and public health agency, is temporarily located in Concord at 5750 Imhoff Drive, Suite I. Contact the District to report mosquito and vector problems online or at (925) 685-9301.
