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Mosquito Response Protocol

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News Release
RI Department of Environmental Management
235 Promenade Street, Providence, RI 02908
(401) 222-2771 TDD/(401) 222-4462

For Release: September 25, 2006
Contact: Gail Mastrati 222-4700 ext. 2402
Stephanie Powell 222-4700 ext. 4418

Mosquito Numbers Down, but Still Infected Mosquitoes in Environment

PROVIDENCE - The Department of Environmental Management announces that test results from one mosquito pool, or sample, from a trap set in Chapmans Swamp in Westerly has been confirmed positive for Eastern Equine Encephalitis. The positive EEE result, the first in Rhode Island this year, was from a Culex species that prefers biting birds and rarely bites humans.

The positive finding came from mosquitoes trapped by DEM staff on September 19 and tested at the RI Department of Health (HEALTH) laboratory. The results were confirmed late this afternoon. As a result, DEM will be setting extra mosquito traps in Chapmans Swamp.

According to Alan Gettman, Ph.D., DEM's mosquito abatement coordinator, it was not surprising to find it in Chapmans Swamp at this time of year. It is in a location where infected mosquitoes have been found in past years toward the end of the mosquito season. Although mosquito numbers have declined throughout the state, the positive result is confirmation that there are still infected mosquitoes in the environment. Therefore, all Rhode Islanders should take extra care to protect themselves, particularly when mosquito-biting activity is high.

Biting activity depends on several conditions. It generally is greatest from dusk to dawn. During the day it decreases in sunny areas at lower temperatures and increases in shady areas at higher temperatures. Biting activity also generally increases with high humidity and with low wind.

Personal protection is the first line of defense against mosquitoes that can carry diseases such as West Nile Virus and EEE and is by far the most effective way of avoiding infection. People should routinely use mosquito repellent and cover up when mosquito-biting activity is greatest. They should place mosquito netting over playpens and carriages outside, and be sure that screens are in good repair. Mosquito repellent should contain no more than 30 percent DEET, and it should not be used on infants.

This year to date, in Rhode Island, 10 mosquito pools have tested positive for West NileVirus, and one mosquito pool has tested positive for EEE. West Nile Virus is well-established throughout the state and, indeed, throughout the country, and EEE has been found in most areas of Rhode Island in prior years. The unusually high number of mosquitoes testing positive for Eastern Equine Encephalitis in Southeastern Massachusetts suggests that the Rhode Island area is this year at a higher than normal risk for EEE, according to DEM officials.

Mosquitoes in Rhode Island are trapped every week statewide by DEM staff and tested at the RI Department of Health laboratory. DEM will normally report mosquito test results once a week on a routine basis, generally by Wednesday, with additional reports as necessary. Routine test results from remaining pools of mosquitoes trapped during the week of September 17 will be included in next week's announcement.

For online information about mosquito-borne diseases, go to DEM's website,, and click on "Public Health Updates", or go to the HEALTH website,, and click on "E" (Eastern Equine Encephalitis) or "W" ((West Nile Virus)) under "Health Topics".


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