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Orange County hunts the Zika mosquito to prevent virus' spread

Jared Dever is driving through a quiet, tree-lined neighborhood in Anaheim. He pulls up in front of a corner home.

"There are probably fifty potted plants in the front yard, which is a good indicator there's probably 500 potted plants in the backyard," says Dever, director of communications for the Orange County Mosquito and Vector Control District.

Properties like this one are nightmares for the vector control agency, he says. But they're heaven to Aedes aegypti mosquitoes, which can carry the Zika virus, as well as dengue and chikingunya. The mosquitoes look for small containers of water where they can lay their eggs.

The Aedes mosquitoes first showed up in California's Central Valley in 2013. Since the beginning of this year, the Orange County mosquito district has found four of them. None carried Zika.

But the virus could still show up, so health officials have gone to war against Aedes aegypti. In neighborhoods where they've found the invasive mosquitoes, Orange County investigators are going door-to-door in search of mosquito breeding sites.

"Every time we find one of these invasive mosquitoes, we have essentially removed one of their players from the battlefield," Dever says.

On a recent morning, agency inspector Pino Rodriguez knocks on the door of a home on a quiet Anaheim cul-de-sac.

"We found the mosquito that carries the dengue fever and Zika virus in the neighborhood so we're checking every single backyard, with the permission of the property owner," he explains.

Rodriguez enters the backyard and begins searching for sources of standing water. He wears long sleeves and long pants. He carries a turkey baster to suck up mosquito eggs in water, chemicals to kill mosquito larvae and a vacuum gun to capture adult mosquitoes that are flying around.

This ground offensive is critical to suppressing the Aedes mosquito. Since 2013, California has confirmed 10 cases of Zika virus; all were in people who contracted it abroad. The work of Rodriguez and the other mosquito investigators is intended to prevent any local transmission of the disease.

But it’s time-consuming work and challenging, because this breed of mosquito is incredibly resilient, explains county entomologist Laura Krueger.

"I think I overheard another entomologist describe them as the cockroach of the mosquito world," Kruger says.

Even the Aedes' eggs are tougher than those of your garden-variety mosquito. Typical mosquitoes lay rafts of eggs on water; the Aedes glue each individual egg to the side of containers, right above the water line.

Krueger says the eggs are also very hardy: They don't dry out in the sunlight, they're not affected by temperature, and they can remain stuck to containers for up to seven or eight years.

They're hard to spot, even for people who are looking for them. The average mosquito egg is one-tenth of an inch; the Aedes egg is one-fiftieth of an inch. To the untrained eye, the eggs look like flecks of dirt.

In a nearby yard filled with fruit trees, resident Ousama Ali Hassan had buried Mason jars filled with water - his homemade irrigation system. Rodriguez identifies them as a prime mosquito breeding ground.

Then one of his colleagues spots mosquito larvae and an adult mosquito in one of the jars.

Rodriguez uses the turkey baster to suck up the larvae and the mosquito. Then he convinces Hassan to remove the Mason jars from his yard.

Later, Rodriguez sends the mosquito sample off to a lab. It turns out this was not an Aedes aegypti mosquito. Still, it's a small victory: the team has eliminated one more mosquito stronghold.