Mosquitoes carrying West Nile virus are in Arizona year-round and are most active a few hours after sunset and before sunrise, a county official said.
Maricopa County officials collect mosquitoes in traps throughout the region, attracting the insects to containers put in trees, David Guerrieri, a field supervisor with the county’s Vector Control Division, said April 30. He spoke at a free workshop on preventing roof rats and mosquitoes.
(See an exclusive video of him discussing how to prevent roof rats here: Video by Richard H. Dyer.)
About 15 people attended the workshop at the Red Mountain Branch Library, 635 N. Power Road in east Mesa.
“They’re filled with dry ice,” Mr. Guerrieri said of the traps. “As the dry ice melts, it produces carbon dioxide, which is an attractant and that attracts the mosquito. And then the mosquito gets caught up in the fan and gets caught up in this net and then we bring them back to our office.”
Officials will fog an area with pesticide from a truck if more than 30 culex tarsalis, or stagnant water mosquitoes, are caught in a trap; if there are more than 300 floodwater mosquitoes swarming; and if any of the samples collected test positive for WNV, he said.
As temperatures start to heat up, so does the mosquito population, according to a press release. Maricopa County Environmental Services Department has reported an increased number of mosquitoes, including one sample that tested positive for West Nile virus. Increased mosquito activity will occur as nighttime temperatures get warmer, according to the release.
West Nile virus
Four out of five people – 80 percent – who have the West Nile virus carried by mosquitoes will not show signs of it, Mr. Guerrieri said.
“They won’t even know they’ve had it. You wouldn’t know unless you got tested for it,” he said.
Of the remaining 20 percent who have WNV, they may have mild signs similar to flu, such as swollen glands and an upset stomach, he said.
“Out of those, 1 percent of those people will come down with meningitis or encephalitis; and one out of 150 infected with West Nile virus could actually die from it. So we do take it seriously and so that’s why we’re here talking about it,” Mr. Guerrieri said.
Meningitis is the inflammation of the lining of the brain and spinal cord and encephalitis is the inflammation of the brain, according to the county’s vector control site, http://www.maricopa.gov/envsvc/VectorControl/.
A map of where traps are set up is on the vector control division’s website, he said. It is under maps and resources. The website also shows mosquito-reducing techniques to use at home to eliminate mosquito breeding.
“We are here to try to reduce the population of mosquitoes to reduce your exposure to West Nile Virus,” Mr. Guerrieri said.
He recommended using insect repellent and covering arms to ward off mosquitoes.
“The best way to protect yourself against mosquitoes is to be aware of when they’re coming out, when they’re most active, when you’re going to be most active,” Mr. Guerrieri said. “Make sure you wear your repellent. Make sure, if you want to, wear a long-sleeved shirt – you don’t have to wear flannel, but something that covers your arms. There is no magic pill, there is no magic button that is going to protect you.”
Joe and Marci Myers were two of about 15 people who listened to Mr. Guerrieri speak on mosquitoes and roof rats and how to prevent them.
Mrs. Myers said the lecture was very informative, “especially looking at the map, to see what the (county) is doing to prevent the mosquitoes and the other things. And what I liked also was being able to go to their website and see what’s going on – to help us understand how they’re helping us,” Mrs. Myers, of the Painted Mountain area of east Mesa, said.
She and her husband have lived in the area for more than 25 years, she said.
“This was a good presentation. The golf course is right behind us and they have … water running, with ducks and all of the animals,” she said.
They have begun seeing mosquitoes at night, Mrs. Myers said.
“We were just out Friday night in the evening and we already felt the mosquitoes, already starting up,” she said.
“What I’ve learned from here is going to my local hardware store and seeing if I can find some of those pheromones that he calls it,” she said.
Mr. Myers said they use an ultraviolet light lamp inside the house for bugs.
“We didn’t know you need a bait. We thought just the light itself would attract them. That’s not enough – you need the bait,” Mr. Myers said.
“When you’re going in and out of the house, the bugs come in with you,” Mrs. Myers said.