Mosquito-Borne Disease Testing Reveals Virus Unseen In The North State For Decades

Sep 1, 2017

We may not have Zika, Malaria or any of the classically terrifying mosquito-borne diseases here in the North State, but our resident insects still carry a number of potentially life-threatening diseases. County agencies are now hard at work to determine which ones are around this summer. Mike Kimball is the manager of Yuba Sutter mosquito abatement. He explains one of the many ways they test mosquitoes for viruses.

Credit Adia White

“Basically you take this vial, slip it in a machine that vibrates it and these beads will beat up 50 mosquitos in there into a paste or liquid and that’s pipetted into trays to do the test,” he says.

He says this year, when they sent a sample of that paste to the University of California, Davis, it came back positive for a virus unseen in the county in decades. It’s called St. Louis Encephalitis. While the name might inspire panic, it’s only rarely deadly.

“It’s going to be very similar to West Nile,” Kimball says. “So most people will not show any symptoms. They won’t even know they had the virus. The ones that do, it will be flu-like symptoms. They will be tired, fever, may have a rash. And then if you’re unlucky, a very small percentage of people will have encephalitis, and sometimes it will be fatal.”

Encephalitis meaning swelling of the brain. It can also cause confusion and paralysis. But again, a very small percentage of people with SLE will notice any symptoms at all and only 1 percent of cases are deadly. So far mosquitos carrying the virus have only shown up in one area in the North State. It’s in Plumas Lake, just south of Yuba City.

Credit Adia White

Meanwhile, they are using a number of other methods to survey the area. Amanda Bradford is an entomologist with Yuba-Sutter mosquito abatement.

She sticks a needle into a chicken’s comb, or the fleshy red frill on the top of its head.

We do a few of those pricks on their comb, and we’ll use a piece of paper, it’s called a nubuto paper and it will absorb their blood really quickly,” she says.

Yuba-Sutter Mosquito abatement has a flock of 49 chickens. They loan them out to property owners in different areas of the county, who get to keep their eggs. Bradford comes by every other week to take blood samples. None of the chickens in the county have tested positive for St. Louis. But in the this particular location, six out of seven have tested positive for West Nile. Bradford says to always take precautions when outside.

“We should absolutely be worried and make sure that we take the correct measures to protect ourselves, and when the mosquitos are out during dawn and dusk,” she says.

West Nile is fairly common in this area, and these results are concerning, but not surprising.

Credit Adia White

It’s the presence of St. Louis that is puzzling. Bradford is glad that none of her chickens have turned up with it yet. As far as how it got here? She can only speculate.

Meanwhile, her colleague, Mike Kimball has a promising theory. He says that the virus is more common in Southern California and that migratory birds, attracted by this year’s wet winter, may have carried St. Louis to region.

“I think we had some birds that came further north and I think that’s what brought it up here possibly,” he said.

For now, all the Sutter-Yuba abatement team can do is increase their surveillance programs and continue to spray hot spots with pesticides to kill as many mosquitoes as they can.