Mosquito district brings in big guns after West Nile virus found early

Aerial foggers will spray mosquito-killing insecticides over sewage lagoons near Grandview tonight after the first mosquitoes carrying West Nile virus were detected there weeks earlier than usual.

“We find West Nile virus every year. The question is when,” said Angela Beehler, manager of the Benton County Mosquito Control District.

The district detected the virus in mosquitoes trapped near Grandview’s sewage lagoons on the Yakima side of the Benton-Yakima county line.

Beehler said a carbon dioxide trap designed to mimic a human being captured a staggering 2,800 insects. Anything over 500 is considered high.

“That number scares me,” she said.

In 2015, there were 24 cases of West Nile virus in Washington, including one death, the most of any year since 2009, according to the Washington State Department of Health.

Hot temperatures coupled with a permanent water and food source at the sewage lagoons conspired to drive up the presence of the Celux genus of mosquito, which carries the virus.

The district increased the concentration of insecticides targeting both larvae and adults. Today’s fogging mission will cost nearly $49,000, including the insecticide and pilot time.

It’s expensive, but Beehler said it pales in comparison to the cost to treat West Nile Virus — about $37,000 per case.

“How many potential exposures do you prevent?” she asked.

The area is not typically inhabited by humans, but it is well traveled by birds. The Celux mosquito prefers feeding on birds to humans and can infect birds, which can then fly into more populated areas where they can infect additional mosquitoes.

Though they prefer birds, the mosquitoes will feed on humans or horses if they’re convenient.

Beehler said the early appearance of West Nile virus doesn’t suggest the mosquito season will end early. Typically, peak human exposure to mosquito-borne illnesses happens in the second week of August.

“This just makes it longer,” she said.

There are no signs of the mosquito strains that carry the Zika virus in Washington.

The state health department encourages area residents to prevent infection by using an EPA-registered insect repellant, wearing long sleeves, pants and socks when outdoors and avoiding mosquitoes that typically feed at night.

Residents are encouraged to empty standing water from flowerpots, gutters, buckets, pool covers, discarded tires and birdbaths on a regular basis to reduce the number of mosquitoes.

This story was originally published June 3, 2016 at 1:44 PM with the headline "Mosquito district brings in big guns after West Nile virus found early."