Mosquitoes in Arizona: Why are there so many? What diseases do these tiny menaces carry?

Shanti Lerner
Arizona Republic

Summertime in Arizona sees some of the hottest temperatures in the United States.  After that dry heat comes the monsoon rain, and rain brings mosquitoes.

These pests, known for their itchy bites are most active and abundant during summer and early fall. Their bites can give you more than just an itch. Mosquitoes spread diseases, some of which can be deadly. 

The most common pathogen that mosquitoes transmit to people in Arizona is the West Nile virus. 

The Republic talked to Shaku Nair, an entomologist and expert in integrated pest management with the University of Arizona, to find out everything you need to know about mosquitoes in Arizona.

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When is mosquito season in Arizona?

According to Nair, most parts of Arizona have mosquitoes year round because they don't get cold enough for a long period of time. In these places, Nair said, bodies of water typically warm up under the sun for a few hours each day and that's enough to sustain mosquito breeding. 

Arizona's highest elevations don’t have mosquitoes all year, but Nair said larvae that winter over in frozen pools can reactivate when the weather warms up. Some species can survive seasons as eggs, without rain or water. When there is a lack of rain, these eggs can survive thanks to human irrigation practices. 

What is the purpose of mosquitoes?

Yes, mosquitos are annoying. But the tiny insects play an important role in the ecosystem. Mosquitoes are part of the food chain and are eaten by bats, birds and even fish. Mosquitoes are also natural pollinators. 

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How many species of mosquitoes does Arizona have?

More than 40 species of mosquitoes are found in Arizona, Nair said. Six or seven species are of concern as disease spreaders.

What do mosquitoes eat?

Adult mosquitoes feed on nectar from flowers and other sources of sugar, such as plant or fruit juices, and honeydew secreted by certain plant sap-sucking insects like aphids. The females of many mosquito species also need to feed on blood for their eggs to develop. 

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What diseases do mosquitoes carry?

The most significant mosquito-borne disease in the world is malaria, Nair said.  Worldwide, mosquitoes also spread dengue, West Nile virus, chikungunya, yellow fever, St. Louis encephalitis, Western equine encephalitis and Eastern equine encephalitis and Zika fever, she said.

What is West Nile virus?

West Nile is a type of RNA virus that causes West Nile fever in humans, other animals and birds. Its preferred hosts are birds and mosquitoes, and it is most commonly transmitted by Culex mosquitoes that feed on infected birds like crows, ravens and jays.

It's not just humans who can contract West Nile virus from a mosquito bite, Nair said. Mammals including horses, dogs and cats are fair game. Even reptiles can be infected. However, compared with humans, animals may not develop the same or as severe symptoms, Nair said. 

The West Nile virus is not easily transmitted between humans. Nair said there have been rare cases in which the virus was passed through blood transfusion, organ transplant and from mother to child during pregnancy or breastfeeding. 

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West Nile virus symptoms             

Eight out 10 people who are infected with West Nile virus develop no symptoms. Some develop a fever and flulike symptoms such as headache, body aches, joint pains, vomiting, diarrhea or rash. Most people recover completely, but fatigue and weakness can last for weeks or months.

Severe illness affecting the central nervous system such as encephalitis (inflammation of the brain) or meningitis (inflammation of the membranes that surround the brain and spinal cord) can develop in some people.

How to get rid of mosquitoes

According to Nair, larvae are easier to manage than adult mosquitoes due to their lack of mobility.

Larvae live in water, so the best way to get rid of them is to reduce places where mosquitoes can breed. Eliminate open containers of water. Such containers can vary from as small as a bottle cap to as large as a poorly maintained swimming pool or a tarp covering a vehicle, Nair said.

Adult mosquitoes can be managed by using traps or spraying pesticides, although these can affect people and pets. Make sure screens on windows and doors are intact and fit snugly. If you're bothered while doing outdoor recreation, apply insect repellent.

Listen:Why is West Nile virus on the rise in Arizona? Valley 101 podcast explores

You can connect with Arizona Republic culture and outdoors reporter Shanti Lerner through email at shanti.lerner@gannett.com  or you can also follow her on Twitter

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