By June 7, 2016

The Real Buzz on Mosquitoes in Arizona

The Aedes aegypti mosquito, which has moved into Arizona, can spread many diseases including the Zika virus. Only females can feed on blood, and this one is doing. PHOTO USDA

The Aedes aegypti mosquito, which has moved into Arizona, can spread many diseases including the Zika virus. Only females can feed on blood, and this one is doing. PHOTO USDA

By Robert Roy Britt — Mosquitoes can be annoying, but a recent outbreak in Anthem’s Arroyo Grande neighborhood made outdoor life all but impossible. Swarms of tiny bloodsuckers got so bad, residents banded together to declare war on the bugs and take back their backyards.

Neighbors “flooded the county with calls,” said Arroyo Grande homeowner Douglas Spurlock.

The county’s mosquito hotline fielded 30 calls from the neighborhood, said David Guerrieri, a vector control supervisor with the Maricopa County Environmental Services Department. “That is a lot compared to what we have previously received for the area,” he said.

The county’s response was prompt because, aside from being pesky, mosquitoes can carry a host of viruses that can infect humans, from West Nile to Zika. They can also carry a nematode that gives dogs heartworm. Among the mosquito-borne viruses Arizona officials worry about are Zika, Dengue and Chikungunya. To date, no one has been known to contract any of these within Arizona—all known cases reported in the state involved infections occurring elsewhere.

But with three cases of the mosquito-borne Zika virus reported in Arizona, officials are on alert. The risk of Zika spreading within Arizona is low, they say, but people are advised to take precautions to help reduce the mosquito population, and to reduce the risk of bites and infections of Zika and other viruses.

A county inspector was dispatched to Arroyo Grande in late May to measure the mosquito problem using a trap. No viruses were detected, but “the inspector witnessed a lot of mosquitoes landing in the area and called the supervisor for a fogging,” Guerrieri explained. The neighborhood sits west of the New River wash and is accessed from New River Road.

Zika Fears

Effects of the Zika virus are typically mild, with common symptoms including fever, rash, joint pain and conjunctivitis. Most people infected don’t even know they have it, experts say. “People usually don’t get sick enough to go to the hospital, and they very rarely die of Zika,” according to the CDC.

But a Zika infection during pregnancy can cause a severe birth defect known as microcephaly; the baby’s head is smaller than normal. The worst cases lead to multiple disabilities.


Maricopa County Environmental Services’ Jim Will checks a mosquito trap used to monitor the prevalence of mosquitoes. PHOTO COURTESY OF MARICOPA COUNTY ENVIRONMENTAL SERVICES

Zika is transmitted by a mosquito species called Aedes aegypti. This mosquito, not native to Arizona, is here now, and it is known to be aggressive during daytime.

“A mosquito that bites a Zika-infected person can then get Zika. If that mosquito bites another person, it can spread Zika to that person,” said Jessica Rigler, chief of the Bureau of Epidemiology and Disease Control at the Arizona Department of Health Services.

“We expect to continue to see travel-associated cases in Arizona, and because we have the right kind of mosquito here, we could also see cases spread locally,” Rigler told In&Out. “However, the likelihood of widespread transmission in Arizona is relatively low.”

In March, when health officials became aware of the first case of a person in Arizona infected with Zika while traveling, “the individual was contacted to ensure she stayed indoors and avoided being bitten by mosquitoes to prevent further spread of the virus,” Bob England, director of Maricopa County Department of Public Health, said in a statement.

West Nile Virus

With all the worry over Zika, it’s important to remember that West Nile is the most common mosquito-borne virus in Arizona. The first known infection in the state was in 2003. In 2015, there were 32 confirmed cases of West Nile in Arizona (26 in Maricopa County) and 71 more considered “probable” in the state.

Mosquitoes pick up West Nile from birds, and can in turn infect other birds, horses and people. Only some species of mosquito carry West Nile, including those that are common in Arizona.

Most people infected with West Nile virus experience no symptoms. About one in five will develop a fever and other symptoms, including headache, body aches, joint pain, diarrhea, vomiting or rash. Fewer than 1 percent develop a serious condition.


Mosquito map

Mosquito traps have been set up at the three dotted locations; one was recently moved to Arroyo Grande. The red square shows the area fogged on May 22. MAP COURTESY OF MARICOPA COUNTY ENVIRONMENTAL SERVICES

What’s Being Done

Maricopa County has long operated a program to monitor, trap and spray (“fog”) for mosquitoes. Each week, the team deploys hundreds of traps, explained Johnny Diloné, a spokesperson for Maricopa County Environmental Services Department. If the traps exhibit West Nile, or a threshold number of total mosquitoes, prevention efforts are undertaken including, in some cases, fogging with a pesticide that kills adult mosquitoes, as was done in Arroyo Grande. [See map.]

The agency is now testing mosquitoes for Zika virus, Diloné said in a phone interview.

The agency used to advise people to be vigilant about mosquitoes at dawn and dusk, when the species carrying West Nile are most active. But with more species to worry about now, and their different habits, the warning has gone 24/7. “Fight the bite day and night” is the advice now, Diloné said.

The state health department coordinates with county agencies and others to identify cases of Zika, West Nile and other diseases, “and are taking actions to prevent disease spread,” Rigler said.

What You Can Do

Mosquito larvae need just a thimble of water to develop, and can hatch in as little as three days. May through October are typically the worst months, when temperatures are warm and rains come to the Valley. Mosquito activity peaks during the monsoon.

This year has been busy. The county’s hotline has received 2,249 mosquito complaints through May 26, a 25 percent increase compared to this time last year.

The Arroyo Grande neighborhood is unique in that the homes were built with catch basins in their yards, which fill with rainwater. Theoretically, the water should dry quickly, but when the basins fill with leaves and debris, or when rain is heavy, water lingers for days. “We got as many neighbors as we could and drilled holes in the catch basins,” Spurlock said.  

Guerrieri, the vector control supervisor, agreed the catch basins are a problem.

Keeping your yard free of standing water is important, but you may want to keep an eye on the neighborhood in general. Many mosquito species travel no more than 300 feet or so. Others are known to range a mile or more.

Catch basins in the Arroyo Grande neighborhood are contributing to the mosquito infestation

Catch basins in the Arroyo Grande neighborhood are contributing to the mosquito infestation. PHOTO BY NADINE SHAALAN

“If you see mosquitoes in your yard, the breeding site could be anywhere near your neighborhood,” Diloné told In&Out. He encourages people who notice an abundance of mosquitoes to do what the Arroyo Grande neighbors did and call the mosquito hotline, 602-506-0700. If needed, the County will contact neighbors (confidentially), and otherwise aim to find the source of mosquitoes, set traps and fog, if necessary.

“We need everyone to do their part,” Diloné said. io


Avoid Bites/Reduce Mosquito Population


Use insect repellent. The CDC considers these safe. Three main types:

  • DEET
  • Icaridin (or picaridin)
  • Oil of lemon eucalyptus

Cover up Pants, socks and long-sleeve shirts offer additional protection.

Keep bugs out Use A/C; make sure window screens are in good repair. Be particularly vigilant from dusk to dawn, when mosquitoes are most active.

Eliminate breeding spots Don’t leave standing water outside—whether in small containers, rain gutters, birdbaths, old tires, or low spots on the ground—for more than two days. Make sure water is circulating properly in a pool or pond.

If you travel to a country where Zika is common, take extra precaution to avoid bites, and if you become infected, contact health officials immediately.

SOURCE Centers for Disease Control, Mayo Clinic

More Information

Advice on Mosquito Prevention:

County Mosquito Hotline
Report unusual mosquito activity or ask questions: 602-506-0700

All About Zika


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