By Dave Rogers
Staff writer
—
Risks of the potentially fatal mosquito-borne disease Eastern equine encephalitis appear to have been abated locally by the region's dry summer, even as other nearby areas remain on heightened alert due to cases being discovered in three Bay State horses and a man in Rhode Island who is in critical condition.
Though health officials continue to warn people to take precautions when outdoors and some pesticide spraying will take place later this month, the lack of rain in this corner of the state has kept mosquito populations down, particularly among the kind that carry the disease.
While concentrations of mosquitoes testing positive for mosquito-borne disease are severe on the South Shore, Worcester County and in parts of New Hampshire, for the first time in several years, no mosquitoes in Greater Newburyport have tested positive for EEE or West Nile virus, according to Walter Montgomery, director of the Northeast Massachusetts Mosquito Control and Wetlands Management District.
The reason, Montgomery said, is the lack of rain in this area, which has been as little as half as much as other parts of the state have received, has reduced breeding habitat for the mosquito species, or so-called vectors, that are known to be carries of Eastern equine encephalitis and West Nile virus.
The same can't be said for the South Shore, which has seen more rain and more mosquitoes. Since the beginning of summer, there have dozens of mosquitoes testing positive for EEE, the majority located in Plymouth County. Three horses have also tested positive for EEE, two located in Plymouth County and another in Worcester County. All of the horses died.
On Aug. 15, the Department of Public Health reported a Rhode Island man had contracted EEE. The patient, a man in his 20s who lives in Newport County, was listed in critical condition.
The Massachusetts Department of Public Health determined the man likely contracted the illness in the southeastern part of Massachusetts. There have been no reported cases of people contracting West Nile virus this year.
In recent years, wetlands areas in Amesbury, Merrimac and Newton, N.H., have proven to be hot spots for EEE, a disease that can cause fatal brain swelling. In 2005, a Newton, N.H., girl died from the disease, and in 2008, a Newburyport man died after being bitten in Maine.
There is no cure for EEE, which is spread from mosquito to mosquito via the birds they feed on. Since the virus was identified in 1938, there have been 100 human cases in Massachusetts. The last outbreak took place between 2004 and 2006, when 13 cases were reported.
The state's last human case was reported in 2008. Locally, however, mosquitoes have tested positive virtually every year since that last outbreak. On Aug. 19 last year, warnings went out after two mosquitoes tested positive in Merrimac. In years when higher concentrations of the virus have been detected, schools have gone as far as to move sports practices inside as a precaution.
The disease gets its name because it often affects horses. The three horses that contracted the disease this year all died, most recently last week in Lancaster.
West Nile virus is spread the same way as EEE but isn't as deadly. Between 2000 and 2008, 60 known human cases have been diagnosed in the state with six people dying, according to the Massachusetts Department of Public Health's website. West Nile has been detected as close as North Andover.
Montgomery said mosquitoes will continue to be trapped and tested for EEE and West Nile virus until the end of summer.
"We trap twice a week all summer long in all of the communities right up until the end of September," Montgomery said.
The mosquito population typically dies out in October when the first frost of the season takes place, he added.
Montgomery said his agency is more concerned with mosquitoes carrying West Nile virus because more of them have been caught. This summer mosquitoes testing positive were found in North Andover and Winthrop.
The agency will likely be conducting a round of aerial spraying sometime in September, concentrating on coastal salt marsh areas where mosquitoes are of particular concern. Montgomery said the public will be notified beforehand via area newspapers when another round of spraying is scheduled.
Dr. Al DeMaria, medical director for the department's Bureau of Infectious Disease, said most of the mosquitoes found in Essex County come from border communities in southern New Hampshire.
"And that tends to spill over to northern Essex County," DeMaria said.
Despite the lack of EEE cases in Essex County, DeMaria stressed the importance of remaining vigilant when it comes to interactions with mosquitoes. DeMaria said people should avoid outdoor activity during dawn and dusk when mosquitoes are most active. If you are going outside, be sure to use mosquito repellent with DEET. Screen windows and doors should be checked to make sure there aren't any holes. And people shouldn't allow water to collect inside bird baths, overturned garbage can lids and other places where water tends to stand for days, he added.
"We know the virus can be out there and why would you put yourself at risk of this unnecessarily?" DeMaria said.
