EagleTribune.com, North Andover, MA

July 22, 2013

Heat, humidity ripe for breeding mosquitoes

Heavy rain, followed by heat spurs breeding

By Doug Ireland

---- — If it seems like there are more mosquitoes biting this summer, it’s not your imagination.

Several days of rain, followed by a week of 90-degree heat, have provided ideal breeding grounds for mosquitoes, including those carrying the potentially deadly West Nile virus and Eastern equine encephalitis. Mosquitoes carrying West Nile have been found in several Massachusetts towns.

“It’s mosquito weather,” said Sarah MacGregor, owner of Dragon Mosquito Control. “Heat, humidity and we’ve had lots of rain — it’s perfect for mosquito production.”

MacGregor’s firm sprays and traps mosquitoes in nearly two dozen Granite State communities. The mosquitoes are then tested by the New Hampshire Department of Health and Human Services.

Mosquitoes carrying West Nile have already been trapped in seven Bay State communities, including Newbury, according to Massachusetts Department of Public Health spokeswoman Anne Roach.

Although the first infected mosquito was found a month ago in Whitman, there have been no human cases, she said. Infected mosquitoes have also been trapped in Belmont, Lynn, Pittsfield, Waltham and Westport, Roach said.

MacGregor said the mosquito problem is the worst she’s seen in several years.

“We’re seeing pretty healthy populations of mosquitoes, especially some of the ones that carry disease,” MacGregor said. “I’m very concerned about the amount of mosquitoes we’re seeing in our traps.”

New Hampshire public health officials have tested 278 pools of mosquitoes in 35 communities over the last three weeks, but there have been no infected mosquitoes, according to Whitney Howe, the state’s vectorborne disease surveillance coordinator.

“There has been a lot of standing water around and that’s a good breeding source,” Howe said. “It’s a good sign there are no positives yet.”

But that can change quickly.

“I do think it could be any day,” MacGregor said.

She said her crews have been busy spraying and collecting mosquitoes for testing. Howe said DHHS has been busy as well.

“We’ve been constantly testing mosquito pools since July 1,” she said. “We are keeping a close watch on what’s happening.”

That same day, DHHS issued an advisory asking that residents take precautions to protect themselves from mosquito bites. They are urged to use insect repellent, wear long-sleeved clothing, remove standing water, and make sure screens on doors and windows fit tightly and do not have holes.

The first infected mosquitoes are usually trapped between mid-July and early August, Howe said.

MacGregor said the rainy weather provides prime conditions for mosquitoes that carry EEE. Species that carry West Nile are more prevalent in hot, dry conditions, she said.

Roach said the populations of mosquitoes that could potentially carry EEE are “slightly above average” in southeastern Massachusetts. Although populations of those that carry West Nile are not particularly large, the weather conditions are favorable for breeding mosquitoes, she said.

Last summer, mosquitoes carrying West Nile or EEE were trapped in several Merrimack Valley and Southern New Hampshire communities.

An Amesbury woman contracted EEE and died Sept. 24. A Georgetown man with the virus died Sept. 27. A horse in Derry contracted EEE and died.

For more information on mosquito-borne illnesses and how to avoid them, visit the state health department websites. In Massachusetts, go to mass.gov/dph/mosquito or call (617) 983-6800. In New Hampshire, visit dhhs.nh.gov. or call 1-800-852-3345, Ext. 4496.