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Mosquitoes in Orange County

Find mosquito tips for avoiding mosquito bites when outdoors and how to mosquito proof your home. Also, learn what the Orange County Mosquito and Vector Control District (OCMVD) does to protect Orange County residents from mosquitoes and the diseases they carry.

Tips for Avoiding Mosquito Bites

Use insect repellent (sprays or wipes): Use an Environmental Protection Agency (EPA)-registered insect repellent. When used as directed, EPA-registered insect repellents are proven safe and effective, even for pregnant and breastfeeding women. The CDC Recommends:

  • Deet
  • Picardin
  • IR 3535
  • Oil of Lemon Eucalyptus (OLE)
  • Para-Menthane-Diol (PMD)

Cover up: Wear light colored, long-sleeved shirts and long pants, and opt for lighter colored clothing when spending time outdoors.

Keep mosquitoes outside: Stay in places with air conditioning or that use window and door screens. If you are not able to protect yourself from mosquitoes inside your home or hotel, sleep under a mosquito bed net.

Mosquito Bite Prevention

Mosquito Proof for Your Home

  • Inspect your property regularly for standing water, and tip or toss any containers filled with water at least once a week.
  • Close all unscreened doors and windows to prevent mosquitoes from entering your home or space; repair broken or damaged screens.
  • Turn over toys, containers, and other objects that cannot be thrown away and properly protect them from the rain or sprinkler water.
  • Pour out water from potted plant saucers to eliminate mosquito breeding.
  • Empty and change water in pet water dishes weekly. Scrubbing regularly also eliminates mosquito eggs deposited along the interior walls of the pet bowl.
  • Regularly clean rain and street gutters. Clogged drains and gutters can create backup that breeds mosquitoes.
  • Remove trash and clutter. This includes discarded tires, buckets, tarps and any other items that could collect water. Ensuring trash can lids fit tightly also helps prevent mosquitoes from laying eggs.
  • Use Mosquitofish in ponds, birdbaths, fountains, unused or “out-of-order” swimming pools, animal water troughs and other standing water sources. Mosquitofish are available free of charge from the OCMVD.

Orange County Mosquito and Vector Control District (OCMVD)

The Orange County Mosquito and Vector Control District’s (District) is responsible for protecting the people of Orange County from the dangers of vector-borne diseases, including Mosquito prevention.

OCMVCD practices Integrated Vector Management (IVM) relying on larvicides, with public health pesticides reserved for situations where other methods would be ineffective to protect public health.

Mosquito surveillance and control activities include:

  • Increase public education and awareness through the regular distribution of media releases, attendance at public events, public lectures, and other similar outreach mechanisms.
  • Monitor mosquito, mosquito-borne disease, and public health pesticide efficacy surveillance activities
  • Conduct routine immature mosquito identification and management

Mosquito Control by Aircraft

The District will conduct adult mosquito control applications by aircraft based on the finding of elevated West Nile virus activity in a specific area, and when all ground-based options are ineffective. Duet ™ will be applied by aircraft to target adult mosquitoes carrying West Nile virus

Illnesses/Diseases from Mosquitos

  • Chikungunya – Although rarely fatal, the symptoms are debilitating and may persist for several weeks. There is no vaccine and primary treatment is limited to pain medication. The mosquito species that transmits this disease are the Asian Tiger Mosquito (Aedes albopictus) and the Yellow Fever Mosquito (Aedes aegypti).
  • Dengue Fever – Dengue is a serious arboviral disease
  • Encephalitis – There are several types of encephalitis strains ranging from mild to very severe conditions.
  • Malaria – Malaria is transmitted among humans by female mosquitoes of the genus Anopheles.
  • West Nile Virus (WNV) – A mosquito-borne disease that was originally found in Africa.
  • Zika Virus – Zika virus is transmitted by Yellow Fever and Asian Tiger mosquitoes. Both species are now found in Orange County. The California Department of Public Health acknowledges that the risk of transmission of Zika virus in California is low.

Types of Mosquitos in Orange County

  • Asian Tiger Mosquito (Aedes albopictus): An aggressive biter that feeds primarily during the day.
  • Yellow Fever Mosquito (Aedes aegypti): A small, black mosquito with white stripes that bite during the day. Also known as the Yellow Fever Mosquito.
  • Ankle Biter Mosquito (Aedes vexans):  A dawn and dusk-biting, stealthy little ankle-biter. They are persistent biters (one female can bite multiple times) and their bites are extremely itchy, which some people have reported to be allergic to. 

Note: Not all mosquitos bite. Female mosquitoes feed on blood because they need it for their eggs. Male mosquitoes feed on flower nectar.

Mosquito Stages of Life

  • Egg: Once laid in water, eggs will hatch in 2 to 3 days.
  • Larva: A mosquito larva looks like a tiny wiggling worm in the water
  • Pupa: A larva becomes a pupa and the adult mosquito develops inside.
  • Adult: Total development time from egg to adult can be less than 1 week during periods of warm weather. The average mosquito will live for about 2 weeks.

Did you know only female mosquitoes suck blood? The males eat nectar only.

Mosquitos within Greater Orange County

Aedes albopictusAsian Tiger MosquitoLucky bamboo plants in nurseries and man-made containersPotential vector for dengue fever, West Nile Virus (WNV), and other encephalitis viruses
Aedes aegyptiYellow Fever MosquitoUrban environment indoors and outdoors in containers that can hold water.Yellow fever, chikungunya and dengue fever
Aedes notoscriptusAustralian Backyard MosquitoUrban environment in outdoor containers that can hold water.Canine heartworm vector
Anopheles franciscanusNoneShallow sunlit pools with algaeNot known to carry disease in California
Anopheles hermsiWestern Malaria MosquitoClear pools with matted algaeMalaria vector
Culex erythrothoraxTule MosquitoPonds, lakes, wildlife refuges, and marshes with tules and cattailsPotential vector for WNV
Culex stigmatosomaBanded Foul Water MosquitoPolluted water (e.g., industrial and agricultural wastes); prefers to bite birdsSecondary St. Louis encephalitis (SLE) vector
Culex quinquefasciatusSouthern House MosquitoPolluted water (e.g.,septic tanks, dairy drains, catch basins, and underground storm drains)Vector of WNV; secondary for SLE and Western Equine encephalomyelitis (WEE)
Culex tarsalisWestern Encephalitis MosquitoAgricultural, commercial, man-made or natural sourcesPrincipal SLE, WEE, and WNV vector
Culex thriambusNoneFoothill riparian habitats, in sunlit pools, along streams and other water coursesPotential vector for WNV
Culex restuansNoneFound in foul waterPotential vector for WNV
Culiseta incidens Culiseta inornata Culiseta particepsCool Weather MosquitoesFresh and brackish waters and containersNot known to carry disease in California
Ochlerotatus sierrensisWestern Treehole MosquitoTreeholes (particularly oak), tires, and containersCanine heartworm vector
Ochlerotatus washinoiWoodland Pond MosquitoOccurs in floodwater habitatsNot known to carry disease in California