Officials on alert for EEE, West Nile

Walter Montgomery isn't taking any chances.

Massachusetts public health officials don't start routine collection and testing of mosquitoes for West Nile virus and Eastern equine encephalitis until June 1. But Montgomery, the top mosquito tracker for many northern suburbs, has been on the hunt for the past three weeks, setting and checking automated traps to make sure his agency's surveillance system is ready.

Ever since EEE cropped up three years ago in mosquito samples in southeastern New Hampshire, and then spread over the border to Essex County, area bug specialists have been on guard.

"Our biggest concern this year will be keeping an eye out for Eastern equine encephalitis. We're still not sure about this, because it is still relatively new to us," said Montgomery, director of the Northeast Massachusetts Mosquito Control and Wetlands Management District. The agency tracks and kills mosquitoes in 31 communities north of Boston.

Since 2004, EEE has been detected in dozens of mosquito samples in southeastern New Hampshire and in Essex County, especially along the border communities of Amesbury, Haverhill, and Merrimac. Several people also have been infected with the virus in both states. New Hampshire reported eight cases and two deaths since 2004, and Massachusetts reported 13 infections resulting in six deaths, including a 58-year-old woman from Everett last September. Public health officials think she contracted the virus during a visit to Hull, in Plymouth County, where mosquitoes carrying the virus are more widespread.

Predicting the risk of bug-borne viruses is tricky in any year, say disease specialists, because part of the equation depends on precipitation. Some mosquitoes thrive in soggy conditions; others flourish in times of drought. And because EEE is so rare -- fewer than 100 cases have been reported in Massachusetts since 1938 -- scientists are still learning about many facets of the virus. On both sides of the border, for instance, specialists are still trying to pinpoint the species of mosquitoes that are most likely to pose disease risks to humans, because not all bite humans.

"We need to try to use our money most effectively for surveillance and control procedures," said Jason Stull, public health veterinarian for New Hampshire's Department of Health and Human Services.

Last year, New Hampshire tested 12,000 mosquito samples, Stull said. This year, the Granite State, home to 47 mosquito species, will be more selective in its testing, trying to put more emphasis on the species that are thought to be the most likely transmitters, he said. The state also for the first time will reimburse communities that spend money to kill mosquito larvae, which breed in catch basins and shallow pools of water. Previously, reimbursements were available only to communities that sprayed adult insects, later in the season.

Larvae "are easier to attack when they are in the water . . . when you can potentially have a large impact on the mosquito season," Stull said.

Back in Massachusetts, Montgomery also has been focusing on killing mosquito larvae in urban communities where mosquito pools last year tested positive for EEE or West Nile: Haverhill, Nahant, Saugus, and Winthrop. Lynn and Peabody have also been targeted because the virus was detected last year in certain birds, which are part of the disease cycle. And Georgetown is included in Montgomery's spring battle plan because EEE was detected in 2005 in one sample of human-biting mosquitoes in that community.

"Surveillance data show an 80 percent reduction in Culex species [mosquitoes that typically transmit disease] in communities where basins are treated, as compared to communities with untreated basins," Montgomery wrote in his mosquito management plan for this season.

Disease trackers in both states say EEE outbreaks typically last two to three years, with as many as 10 to 20 years between occurrences. With New Hampshire detecting its most recent outbreak starting in 2004, and Essex County recording its first ever documented signs of the virus in 2005, officials aren't sure what to expect this season. But they remain vigilant.

"Upstate New York this past season experienced what appears to be a fourth year of an EEE cycle," Montgomery wrote in his mosquito management plan. "Therefore, the district will continue to enhance and expand our EEE surveillance and preemptive control strategies."

Kay Lazar can be reached at klazar@globe.com.

Northtalk
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