imageOur county’s diverse ecological regions create a range of mosquito sources. The District regularly surveys more than 10,000 acres of marshland along the waterfront, acres of irrigated farmland in the eastern county and numerous ponds, creeks and residential sources countywide in an effort to control the species of mosquitoes currently in existence while also on the lookout for the potential arrival of new and invasive mosquito species. The county is also home to many insects that resemble mosquitoes.

Upon request for service, the District will inspect your property for mosquito problems and provide advice on controlling their populations.

With 23 different kinds of mosquitoes that inhabit a variety of water sources, it’s important that the homeowner or caller provide our District employee with a mosquito sample that can be identified to determine its possible source, however we will still be able to provide service without a one (results may be limited without a sample). Simply swat a mosquito and save it or tape it to a piece of paper for the District employee.

The District also appreciates Contra Costa county residents doing their part to protect public health by reporting non-maintained swimming pools (pools that are not chlorinated or filtered). Residents can submit swimming pool reports anonymously by phone (925) 685-9301 or online.


imageZika Virus: Questions Answered

Zika virus is transmitted by Aedes aegypti mosquitoes (also known as yellow fever mosquitoes) and by Aedes albopictus mosquitoes (also known as Asian tiger mosquitoes). These mosquitoes are not native to California. However, since 2011 they have been detected in several California counties. READ MORE.


image New and Invasive Mosquito Species

Aedes aegypti and Aedes albopictus have the potential to transmit several viruses, including dengue, chikungunya, Zika, and yellow fever. None of these viruses are currently known to be transmitted within California, but thousands of people are infected with these viruses in other parts of the world, including in Mexico, Central and South America, the Caribbean, and Asia. READ MORE.


image Should We Worry About West Nile Virus?

West Nile virus is dangerous. It arrived into Contra Costa County in 2004, a mere five years after it first entered the Western Hemisphere into New York in 1999. It's now endemic - established and ingrained into our environment. READ MORE.


imageAdult Mosquito Control

Adult mosquito control (spraying) to control adult mosquitoes only occurs after surveillance and testing indicate either the presence of West Nile virus in an area, or if the number of mosquitoes exceeds the public health threshold. The majority of our mosquito control is completed when the mosquitoes are in the water in their larval form. We spray for adult mosquitoes when our surveillance data meets the criteria to perform this action. We encourage residents to sign up and receive free email notifications that include adult mosquito control schedules, interactive maps, product information, and more.


imageInsects That Resemble Mosquitoes

Contra Costa County is home to twenty three species of mosquitoes. There are also several types of insects located throughout the county that many people perceive as a mosquito, but actually are different species of insects. READ MORE.


image West Nile Virus Mosquitoes of Contra Costa County

Out of the 23 species of mosquitoes found in Contra Costa County, two species are known transmitters of West Nile Virus. READ MORE.


image The Western Tree Hole Mosquito

The Western tree hole mosquito (Aedes sierrensis) receives its name because the immature stages of this mosquito species are frequently found in water contained in rot-holes of trees. READ MORE.


image The Mosquito Life Cycle

Mosquitoes have four life stages; egg, larva, pupa, and adult. The first three stages require standing water for their development. The female mosquito lays her eggs either individually or in clusters, which is called an egg raft. READ MORE.


image How to Mosquito-Proof Your Backyard

Mosquitoes need very little water to lay eggs and produce hundreds, thousands, even millions of mosquitoes. Adult mosquitoes can acquire diseases such as West Nile virus, which is present in Contra Costa County. Dump out standing water and prevent mosquito production. READ MORE.


imageMosquito Diseases

Some species of mosquitoese are involved in the transmission of important disease-causing agents (pathogens). In Califonria, these diseases include encephalitis viruses, malaria, and dog heartworm. READ MORE.


imageMosquito Surveillance and Trapping

The goal of our surveillance program is to prevent mosquito problems before they happen. We monitor mosquito populations throughout the county by regularly inspecting all bodies of water known to harbor mosquito larvae. READ MORE.


image Mosquito Control

Our mosquito control program is based on the principle of Integrated Vector Management (IVM). It is most effective to control the larval stages since they are concentrated in a smaller area and cannot fly away. READ MORE.


image West Nile Virus Information

West Nile virus is a viral disease of birds that is transmitted from bird to bird by way of a mosquito bite. It can occasionally cause meningoencephalitis (inflammation of the brain and spinal cord). READ MORE.


image 23 Mosquito Species of Contra Costa County

That's right. Contra Costa County is home to a variety of mosquito species that vary regarding flight range, habitat, biting behavior, and potential carrier/transmitter of disease. READ MORE.


image Why Do We Use Adulticides?

It is generally agreed by mosquito control experts that controlling larval mosquitoes while they are still restricted to their aquatic habitat is the most effective way to reduce adult mosquito populations and therefore reduce the risk of disease. READ MORE.


imageWhere Do Mosquitoes Go in Winter?

Mosquitoes are usually thought of as a summer phenomenon, like barbecues or days at the beach. But have you ever wondered what happens to them during the "off season"? The answer may be more complicated than you think. READ MORE.


imageHow YOU Can Protect Yourself

Protect yourself from mosquitoes and the diseases they transmit by practicing the District's "7 D's of mosquito prevention." READ MORE.

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