Mosquitoes redux

It’s happened before. Spring rain clouds in Sacramento give way to a different kind of cloud as summer heats up: swarms of bloodsucking mosquitoes.

And with the insects comes the possibility of another outbreak of West Nile virus, a mosquito-borne disease that has menaced the region for the better part of a decade. After a late spring, and even downpours as recent as last week, drenched the area with above-average rainfall, Sacramento could experience another epidemic, according to David Brown, manager of the Sacramento-Yolo Mosquito and Vector Control District.

“I think conditions are unfortunately setting themselves up for a potentially bad year,” said Brown, adding that the district has been busy warning area residents about leaving standing water in their yards to prevent another outbreak.

Yet public health officials hope Sacramento can avoid a crisis like the one that happened in 2005, when there were 177 reported human cases of West Nile virus and one death. While the disease is still present in the region, Sacramento County only had 27 reported human cases in 2010.

“I do think we are unlikely to see as bad a year as 2005 again,” said Dr. Glennah Trochet, public health officer for Sacramento County. “We may have a segment of our population that is now immune.”

Last year, despite the smaller number of reported human cases, the district still conducted aerial spraying more than 72,000 acres in Sacramento County with EverGreen 60-6, a pyrethrin-based insecticide that the U.S. Environmental Protection Agency says is safe.

Brown said the decision to spray from the air depends on whether the public follows guidelines to eliminate standing water and use preventative measures, like adding mosquito fish to ponds and pools. It’s usually a last resort once an epidemic hits.

“Really, our intent is to break the transmission cycle when we have to do those types of treatments, particularly in urban areas,” Brown said, adding that just five infected mosquitoes in a sample of 1,000 is considered an epidemic. “If we can get a certain level of control that breaks the transmission cycle, we consider that to be effective.”

The treatments initially sparked controversy in 2005, when spraying opponents angrily protested the aerial insecticide treatments at informational meetings held by the district. But in the past few years, Brown said he hasn’t seen as much opposition to the spraying.

“I think we demonstrated that, no, we didn’t have the devastating effects on the environment that was being discussed by some of our anti-spraying advocates,” Brown said.

Not true, opponents claim. Kim Glazzard, executive director for Organic Sacramento, said the controversy only disappeared because anti-spraying advocates thought the district had recognized the virus was now chronic endemic to the region—meaning birds and animals that survived the epidemic are immune and will be less likely to pass on the disease.

“It was shocking that the mosquito district decided to go ahead and spray anyway last year,” said Glazzard.

Others are hoping the district can continue using nontoxic measures to contain the mosquito population. Glazzard said people can protect themselves with organic remedies such as mugwort and citronella sprays that are available at many area natural-food stores.

“There’s significant scientific research that says the spraying isn’t the best way to solve this problem,” said Asael Sala, a community organizer with Pesticide Watch, an environmental group based in Sacramento. “There are other ways to go about doing this, such as using the larvae-eating fish or implementing integrated pest-management techniques that would actually be more effective at getting at the root cause of the West Nile virus.”

Brown maintains that the spraying is safe and has little ecological impact. “I think there was a concern about the spraying and, in some cases, I think they thought it was going to have devastating effects on the environment,” he explained, “and yet we were very open about what we were doing.”