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Mosquito control agencies already hard at work

Bill Mehaffey, district supervisor for Northeast Mass. Mosquito Control & Wetlands Management District, demonstrates how to he checks for mosquito larva in an area of marsh in Essex.
Bill Mehaffey, district supervisor for Northeast Mass. Mosquito Control & Wetlands Management District, demonstrates how to he checks for mosquito larva in an area of marsh in Essex.(Mark Lorenz for The Boston Globe)

The late snow melt and dry spring kept the early-season mosquito population normal to light in most places. But the downpours that spotted late May and June brought a spike of summer mosquitoes in floodwater areas that were soaked.

As the summer kicks into gear, mosquito control experts and the state's Department of Public Health already have begun the season-long effort to maintain and monitor the mosquito population, and to educate the public on the need to take precautions.

Rainfall changes always make mosquito predictions tougher.

"There are years where you get massive rains, where it might drop six inches of rain in a few days, and that will change everything," said David Henley, superintendent of both the East Middlesex and Suffolk County mosquito control projects, which cover 28 communities north and west of Boston.

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"High rain totals will increase the mammal-biting mosquito population, but there have been studies that show that West Nile virus is a greater risk during abnormally hot summers," Henley said. Culex pipiens — the common backyard mosquito that is the primary carrier of West Nile — breeds best in water that collects in containers such as catch basins, neglected swimming pools, and bird baths, Henley said.

There have been no early findings of any kind of virus, but when it comes to managing mosquitoes, the experts say, they hope for the best and plan contingencies for whatever comes. "Right now, we're just waiting," said Ellen Bidlack, entomologist for the Plymouth County Mosquito Control Project, which covers 28 towns south of Boston.

The insect is a carrier for both West Nile virus and Eastern equine encephalitis. West Nile virus is easier to contract, and 70 percent to 80 percent of those infected experience no symptoms, according to the Centers for Disease Control and Prevention. About one in five people will develop flu-like systems, and less than 1 percent will develop a serious neurologic illness, according to the CDC.

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"EEE is more deadly, and people are likely to have long-term neurological problems if they get it," Bidlack said. "In point of fact, there are more West Nile cases in a year than EEE, generally."

The state's 11 mosquito control agencies spend their summers sending technicians into the field to treat catch basins and other potential breeding spots with larvicide; to regularly survey mosquito traps for mosquitoes that are then tested for virus; and to spray pesticides either as a regularly scheduled precaution or in response to findings of EEE or West Nile virus in samples or in areas where there are large populations.

"For years, we were basically nuisance control, but when West Nile hit New York City in 1999, there was a big change to public health," said Bill Mehaffey, district supervisor for the Northeast Massachusetts Mosquito Control and Wetlands Management District, which services 33 cities and towns, primarily in Essex County.

There are 11 agencies that manage mosquitoes in Massachusetts, each one independent and with different approaches. Northeast Massachusetts and East Middlesex, for example, develop individual management plans for each member city and town, while Plymouth County has the same management plan for all its communities. East Middlesex mosquito technicians often travel on bicycles, something that's practical in urban areas but less so in communities where catch basins are spread farther apart.

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In East Middlesex and Suffolk counties, Henley's technicians have sprayed in sections of 10 communities — West Roxbury, Hyde Park, East Boston, North Reading, Reading, Wakefield, Bedford, Sudbury, Framingham, Weston, and Waltham — after finding large numbers of infected mosquitoes in traps. At the request of residents, Plymouth County Mosquito Control has been truck-spraying weekdays from 2 to 5 a.m. in communities south of Boston, where EEE has historically been a high risk.

So far this season, the Northeast Mosquito Control & Wetlands Management District has done salt marsh aerial spraying from Salisbury to Ipswich twice after testing yielded high numbers of mosquito larvae in the wetlands. It also is responding to about 90 resident requests each week for truck spraying throughout the district.

While the tools used to control and monitor mosquito populations are worthwhile, public health experts advise that the best protection is taking precautions: applying insect repellent with DEET (or other approved chemicals) while outdoors; being mindful of mosquito activity, particularly during peak activity hours at dawn and dusk; wearing light, long-sleeved shirts and pants and white socks when outdoors; and repairing broken screens to keep mosquitoes out of the house.

Another important precaution is to drain standing water from items such as bird baths, gutters, or flower pots, which offer the prime breeding environment for the type of mosquito that carries West Nile virus.

"We don't want people to be scared of mosquitoes or to go outside," said Dr. Catherine Brown, state veterinarian for the Department of Public Health. "Awareness and personal protection. It's just part of the summer."

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David Rattigan can be reached at DRattigan.Globe@gmail .com.