Mosquito concerns in wake of the North Bay Fires

SANTA ROSA, Calif. (KTVU) - In the wake of the North Bay Fires, came mosquitoes, perhaps millions of them. They found brackish swimming pools in burned backyards – an ideal environment to lay eggs.

Now, a few weeks later, they are about to hatch, and vector control officials are concerned. 

"Oh, tens of thousands of mosquitos are in just one pool, " said Nizza Sequeira of the Marin/Sonoma Mosquito and Vector Control District. 

"These mosquitos can fly over a mile," said Sequeira. "So whether we're in the burn area or have residents on the outside of those areas, the mosquitos will fly into those neighborhoods." 

And she predicts people on the fringe of the fire zones will notice it immediately. 

"They will just go outside in the evening, and they will just be instantly attacked by mosquitos biting them." said Sequeira. 

Aerial maps show the neighborhoods of northeast Santa Rosa: Fountain Grove, Coffee Park, and Larkfield dotted with sparkling blue pools, hundreds of them in the burn areas.  

"This pool was probably fully maintained up until the fire damage, so it just turned that fast, " said vector control technician Kevin Beardsley, taking samples from several polluted pools in Fountain Grove. 

The water was alive with larvae, in various stages of development, the largest resembling pollywogs.

"You're looking at three to four days before the bigger ones hatch off into adult mosquitos," Beardsley said. "So in an average pool, thousands of mosquitos could hatch off within a week if we don't treat it, so we're trying to get out as quickly as possible to all of them." 

Beardsley and a dozen other technicians are spread out across the fire escape, checking about fifty pools and hots tubs each day. When they find the larvae, they toss packets of biological larvaecide into the pool, which kills them, but must be re-applied every few weeks. 

And the oncoming winter weather will add to the challenge. "When we go into the rainy season, foundations will fill up with water, so we might have to go house to house, checking every one," said Beardlsey.

"Our next step is looking for septic tanks where the lids may have melted off,” said Sequeira. "As rains start, anything in these areas that can hold water." 

Burned properties are scattered with planters, buckets, barrels, and debris – all potential places for mosquitos to lay eggs. 

The district was already monitoring about 500 pools in Santa Rosa, known to be poorly-maintained, and in need of surveillance. Now that number could double, even triple, overnight due to the fire disaster. 

So far, teams have checked more than 300 pools, and 90 percent tested positive for larvae.   

Considering what fire victims are grappling with, the condition of their swimming pools is probably insignificant. But the technicians occasionally run into homeowners when visiting the ruined sites. 

"It's heartbreaking, and we try to interact with those people," said Beardsley. "Because our focus is mosquitos but you can't forget the people and their loss." 

In time, swimming pools and hot tubs will be drained, but because of contamination issues, it's is not a simple process.  

The hunt for mosquitos is also proceeding in Bennett Valley and the Sonoma Valley, where the Nuns Fire destroyed homes, and blackened backyard pools.  

So far, the species of mosquito being found is very common, and not associated with West Nile Virus, but that could change as pool waters deteriorate further, attracting other types of mosquitos.