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Vector Control

Mosquitoes in the Tahoe Area

Image of Mosquito The mosquito population in the Tahoe Basin is most active in the spring and early summer. Each mosquito species has a season when it is most active and a range of preferred hosts. Most mosquitoes will feed on more than one type of host. The female mosquito needs a blood meal in order to produce eggs. Blood meal hosts range from reptiles, amphibians, mammals, birds, to humans. All mosquito species are potential vectors of organisms that can cause disease to pets, domestic animals, wildlife, or humans.

Common Tahoe Area Mosquitoes:

Aedes (cataphylla, hexodontus, increptius, tahoensis) Image of a Mosquito Aedes

These mosquitoes are known as "snow melt" mosquitoes. They occur in snow melt pools and usually do not fly far from their larval sources. They are day or night biters.

Aedes ventrovittis
The "little black mosquito of the high Sierras" is a small mosquito that breeds in shallow grassy meadow pools. Females do not fly far from larval sources, and are vicious day biters of large mammals including man.

Culex tarsalis Image of a Mosquito Culex

This is the "Encephalitis mosquito" and can transmit the encephalitis virus to humans. Immature stages develop in any standing freshwater source. Females are night feeders mostly on birds, but will switch to mammals including man.

Culiseta (inornata, incidens, impatiens)
These mosquitoes breed in ponds, basins, and artificial containers. Females actively feed at dawn and dusk mainly on large domestic animals and man.

Mosquito Borne Diseases:

Encephalitis (sleeping sickness)
Encephalitis is a flu-like illness caused by a virus. Symptoms include high fever and inflammation of the brain. Severe infections are usually marked by acute onset, headache, high fever, disorientation, and occasionally convulsions. Most common in California is Western Equine encephalitis (WEE) and St. Louis encephalitis (SLE). Mosquitoes become infected while feeding on birds that carry the virus. The mosquito can then infect humans with the virus when they bite. 

Malaria is also a flu-like illness caused by a protozoan. Symptoms include fever, shaking chills, headache, nausea, and ending with profuse sweating. After an interval free of fever, the cycle of chills, fever, and sweating is repeated every 2 to 3 days. Man is the only important reservoir of human malaria, and mosquitos become infected while feeding on other humans that harbor the parasite. The disease is transmitted when an infective female anopheline mosquito bites a human. 

West Nile Virus (WNV) 
This is an emerging infectious disease that was first recognized in the United States in 1999 in the New York area. It was associated with a die off of birds in the area, especially crows. Symptoms in man include low-grade fever, slight fatigue, aches, and mild headache. The elderly and individuals with immunocompromised systems may experience severe headache, neck stiffness, high fever, various central nervous abnormalities, and sometimes death. This virus has been detected in California.

Canine Heartworm
This is a disease that affects dogs only. It is caused by a worm that damages the lungs and heart of a dog. Symptoms are not evident until later stages of the disease. Dogs may develop a chronic cough, tire easily, and accumulate fluid. The heartworm parasite can cause lung, liver, and kidney damage, or death. Mosquitoes attain worms by feeding on infected dogs, coyotes, or foxes.

Precautions Against Mosquito Bites:Image of a Mosquito Aedes Feeding

Avoid activity outside at dawn and dusk when mosquitoes are most active.

When engaging in outdoor activities, wear long pants, long sleeve shirts and other protective clothing and apply insect repellant according to label instructions.

Keep infants indoors during peak mosquito hours. If outside, cover cribs, bassinets or playpens with suspended mosquito netting.

Identify and eliminate all sources of standing water around property that can support mosquito breeding.

Horses also are susceptible to mosquito-borne viruses and should be vaccinated each year.