THIS STORY HAS BEEN FORMATTED FOR EASY PRINTING

Mosquitoes already? That’s the buzz

Rains gave them a head start

By Stephen Smith
Globe Staff / May 28, 2010

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The epic rains of March and April, followed by mild nights this month, have spawned an unwanted legacy as Memorial Day weekend dawns: swarms of mosquitoes buzzing and biting weeks earlier than usual in Massachusetts.

At the offices of the Norfolk County Mosquito Control Project, the phone has jangled with increasing urgency as residents call with a lament and a plea: There are lots of bugs, the callers report. Come and do something.

Workers have taken to yards with traps and harvested bumper crops of mosquitoes. This week, spraying to kill adult mosquitoes began in the most bug-besotted swatches of Norfolk County.

“It is very unusual,’’ Chan Suom, the entomologist at the Norfolk mosquito office, said yesterday. “We don’t see this kind of mosquito abundance this early.’’

David Henley, superintendent of the East Middlesex Mosquito Control Project, has seen the insects when he’s working, and when he’s not. They have intruded on nighttime tennis matches, and stalked him as he nurtures freshly planted grass.

“The whole mosquito cycle has been pushed ahead,’’ Henley said. “And they’re actively biting people because we’ve had so many warm nights.’’

So far, those bites are more stinging nuisance than nagging health threat.

There is no evidence that West Nile virus or eastern equine encephalitis are widely circulating right now. That isn’t much of a surprise: It takes months of interplay between bugs, birds, and humans for those viruses to get amplified to the point that they present a threat to people. That point is usually reached later in summer or early in the fall.

Last year, there were no human cases of West Nile or eastern equine encephalitis. But disease trackers are keenly interested to see whether the early debut of mosquitoes foreshadows an early arrival of the illnesses they can carry.

“You’re starting with a higher population,’’ said Dr. Alfred DeMaria, top epidemiologist at the Massachusetts Department of Public Health. “And mosquitoes beget mosquitoes.’’

Still, if the weather turns dry for several weeks, it could deprive mosquitoes of the habitat they need to create their progeny, reducing prospects that diseases will start spreading.

“The only thing that’s harder to predict than mosquitoes,’’ DeMaria said, “is influenza.’’

The rain torrents of early spring provided one of the three necessary ingredients for mosquito propagation. The other two are temperature and sunlight, Suom said. And there was ample warm weather in spring.

The water and warmth thawed blankets of ice that can, in cooler, drier years, extend into March in New England wetlands. So slumbering mosquitoes got an early wake-up call, and their eggs bathed in water that assured larvae would appear.

In some cases, Suom said, mosquitoes began their life cycle as much as a month ahead of schedule.

Henley’s crews, for example, began to see adult mosquitoes in late April.

“I think a lot of nature came out early,’’ Henley said. “It’s usually the second or third week in May when people start getting bitten.’’

Traps in some spots have lured 1,000 mosquitoes, an unseasonably high catch. Norfolk County mosquito counters have found bountiful populations bordering the Neponset and Charles rivers.

In Middlesex County, there has been spraying from air and ground to combat developing mosquitoes before they can take flight. And in Norfolk, the ground-level spraying this week concentrated on the adult insects.

State public health authorities yesterday issued their annual warning to hikers, gardeners, and barbecuers to cover up and slather on bug repellent, especially between dusk and dawn. They also urged homeowners to fix tattered screens and drain potential mosquito breeding grounds, including gutters, trash cans, recycling bins, and wading pools.

DeMaria, the state epidemiologist, said he advises protective measures now even though there’s no suggestion mosquitoes are spreading disease.

“It’s dangerous to say that you don’t need to worry before July 3 or whenever,’’ he said. “We want people to start precautions before the risk comes up.’’

Stephen Smith can be reached at stsmith@globe.com.

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