Mosquitoes collected this week in Beverly, Hamilton and several other Essex County communities have tested positive for West Nile virus.
Health officials in Hamilton, however, have decided not to spray mosquito insecticide. It’s a change from last summer, when insecticide was sprayed multiple times after infected mosquitoes were found in Hamilton.
This time around, Hamilton’s Board of Health decided that insecticide spraying is not the best option to reduce the risk of human infection, said Leslie Whelan, the town’s health agent.
“We’ve been preparing for this moment (a positive West Nile test),” said Whelan. “The Board of Health has been researching this for about a year now ... (and found that) spraying is the least effective means of controlling mosquito-borne disease in humans.”
“(Truck-sprayed insecticide) only kills mosquitoes for 20 minutes, and then new mosquitoes are hatching. And it’s toxic for the environment,” she said.
The state releases results of the week’s mosquito testing each Friday afternoon. In addition to Hamilton, mosquitoes in Beverly, Swampscott, Middleton, Saugus, Lynn and several other Essex County towns tested positive for West Nile virus this week.
West Nile mosquitoes were discovered in Beverly in the first week of August, and insecticide was sprayed in portions of Beverly in the following week. Beverly City Hall was closed yesterday afternoon and city health officials could not be reached for comment.
This week marks the first time a West Nile mosquito has been found in Hamilton this summer. The mosquito was collected Tuesday in a trap on Chebacco Road, said Whelan.
Hamilton’s Board of Health has been researching and discussing whether to spray since last summer, after several residents called with concerns about spraying, said Whelan. The board made the decision not to spray this spring and reaffirmed its choice at a meeting last week.
Municipalities often decide to spray because it’s the only thing a government agency can do, widespread, as a precaution against mosquito-borne illness, said Whelan.
However, the best defense is the measures residents can take on their own, such as avoiding going outdoors when mosquitoes are out, using bug spray and draining standing water where mosquitoes breed, she said.
“That’s the most important public health message there is about mosquitoes,” Whelan said. “... The most effective thing is to avoid getting bitten.”
Municipal spraying can give residents a “false sense of security,” she said, and they lower their guard.
State health officials have said two people — residents of Norfolk and Plymouth counties — have contracted West Nile virus this year. The disease can be fatal, but health officials estimate that fewer than 1 percent of people infected with West Nile develop severe illness.
Last year, mosquito samples collected in Hamilton tested positive for both West Nile virus and Eastern equine encephalitis, or EEE, and the town sprayed insecticide multiple times. Hamilton’s Board of Health adopted a ban on organized outdoor activities in the first week of October after a horse in neighboring Essex contracted EEE.
Since then, Hamilton Board of Health members have been researching the pros and cons of spraying, talking with state health officials and the Northeast Massachusetts Mosquito Control, said Whelan.
“All insecticides are toxic,” she said. “They aren’t without risk.”
Beekeepers in several North Shore towns have expressed concern over mosquito spraying recently, out of concern for their bees. Whelan said several Hamilton residents called health officials with concerns about last year’s spraying, but they were not beekeepers.
Bethany Bray can be reached at firstname.lastname@example.org and on Twitter @SalemNewsBB.