Watching For The Zika Virus In Maricopa County, One Mosquito At A Time

Published: Thursday, November 17, 2016 - 9:23pm
Updated: Friday, November 18, 2016 - 12:11pm
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(Photo by Lauren Gilger - KJZZ)
When Howe removes the net full of mosquitoes, he puts each net in a bag that's dated and labeled.
(Photo by Lauren Gilger - KJZZ)
Mosquitoes are broken down into a "mosquito soup" and then tested in the lab.

Late one morning, Nathan Howe is out at the Tres Rios Wetlands west of Phoenix, dismantling a mosquito trap he set up the night before.

The trap looks like a high school science project. There’s a bucket filled with dry ice hanging from a post and hanging from it is a little battery-powered fan and a long, skinny net.

“We use dry ice, it attracts them," Howe said. And the fan? “It pulls them down inside of the net and keeps them there.”

And, sure enough, inside the net are a few dozen tiny mosquitoes that he’s caught.

Howe takes the net off, and places it a plastic bag with the date and location written on the outside. “Just put them in a bag and close it up, then we put it in the cooler with dry ice so it keeps them cold until we can get them back to the lab,” he said.

Howe is a field tech for Aquatic Consulting and Testing, a contractor hired by the city of Phoenix to track mosquitoes here.

Just a few months ago, the potential spread of the Zika virus dominated the news. A few years before that, it was West Nile virus that had people worried.

But, whether or not the public is focused on a dangerous mosquito-borne illness, people like Howe still fan out across the country every day, collecting thousands of mosquitoes and testing them, to keep the public safe.

The traps Howe is collecting give off carbon dioxide (CO2) from the dry ice, which some breeds of mosquitoes are attracted to. But, the Aedes aegypti mosquito, the one that’s spreading the Zika virus, is attracted to something else.

“The bait we use, rather than CO2, we tend to use an artificial bate that smells like humans because they are more attracted to that,” said Rick Amalfi, the vice president of Aquatic Consulting and Testing.

He said they’ve been getting more requests lately to track Aedes aegypti mosquitoes in particular, because people are concerned about the spread of the Zika virus, which can cause severe birth defects in unborn babies, among other complications.

“We have seen not huge numbers of those mosquitoes, but we seem to collect them more frequently than we used to,” he said.

These mosquitoes are ankle biters, Amalfi said, “They go low!”

And, for that, and a few more reasons, he said they can be harder to track than the ones found out here in the wetlands.

“Your sprinkler system goes off at night and there’s a bucket or something left in the yard and the water gets in there, the floodwater mosquitoes, the Aedes aegypti mosquito, will love that!” he said.

And, they feed all the time, not just at dusk and dawn, so, Amalfi and his team leave their traps out for a full 24 hours.

“We have, actually, motor cycle batteries power those,” he said.

After they collect the dozen nets full of mosquitoes this morning, they take them to a lab where they’ll be frozen, sorted by breed and then tested for various diseases, from West Nile Virus and dengue fever to Zika.

John Townsend, division manager for Maricopa County Vector Control, said his department has nearly 800 traps set throughout the 2,500 square miles of the Phoenix metro area.

When they are collected and brought into the county’s lab, they’re put into a DNA amplifier machine to be tested.

“And if there’s any virus present that they’re looking for, in those mosquitoes, it’ll show up in here,” he said.

There are no local cases of Zika yet here in Maricopa County, but, Townsend said there are about 50 travel-related cases that he and his team are tracking closely.

“We will go out there, trap the area where those people are sick, and collect those mosquitoes to make sure that we don’t have any locally acquired mosquitoes that are infected that could potentially spread those diseases to other people that haven’t gone anywhere,” he said.

And Townsend said the Zika virus is different than most mosquito-borne illnesses, because it can be transmitted sexually, as well as through mosquitoes.

“All it takes is, seems like a plane ride nowadays to get something spread from one area to the other,” he said.

Townsend thinks it’s pretty unlikely that Zika will spread locally here because of their robust monitoring program.

“We do our job, we sample, we do our surveillance,” he said. “But, you know, even in a 2,500-square-mile area, there’s so many areas that we can’t get to, and don’t know about.”

So, he said it comes down to you.

“You can do something," he said. “You can look for areas that are breeding mosquitoes in your backyard.”

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