Days and nights are cooler at this time of year and usually less buggy.

That may not be entirely true when it comes to mosquitoes, although with a hard frost any one of these days the pesky insects would be gone.

“This is not the time to let down your guard,” says Allan Gettman, mosquito abatement coordinator for the Department of Environmental Management.

Last week DEM announced a horse in Tiverton tested positive for Eastern Equine Encephalitis (EEE). The animal was euthanized. This was the first death of a horse this year attributed to EEE, a disease transmitted by mosquitoes.

Gettman said cases of EEE in humans is very rare, but carries with it a high level of mortality. He said there have been two cases of EEE in humans in the northeast this summer, one that killed a man in upstate New York and another affecting a 3-year-old New Hampshire girl. He said the girl went into a coma, but now is recovering.

EEE, he said, is largely carried by mosquitoes in rural areas while West Nile Virus that is less deadly to humans is more commonly found in urban areas.

Last week the agency announced that test results from 54 mosquito pools, or samples, from 32 traps set during the week of Sept. 14 are negative for both West Nile Virus and Eastern Equine Encephalitis (EEE.) As was previously reported, one mosquito pool in the Woodlawn/Fairlawn area of Pawtucket has tested positive for West Nile Virus. There are no traps in Warwick, Gettman said, although there is on the Cranston/Warwick line.

Gettman said the mosquito population shot up during August because of the especially rainy July. Now, he said, the numbers are declining as mosquitoes die of old age. He said the first “hard frost” would pretty much “wipe them out.”

Nonetheless, the department continues to urge people to take precautions.

In its weekly report of mosquito tests, DEM urges residents to eliminate mosquito breeding grounds from yards by removing anything that holds standing water, such as old tires, buckets, junk and debris, clean gutters so that they drain correctly and maintain swimming pools properly.

Mosquitoes breed in standing water. Just one cup of standing water can produce hundreds of mosquitoes. Avoid mosquito bites by using screens on windows and doors, covering up at dawn and dusk and putting mosquito netting over playpens and baby carriages when they are outside. Also, use mosquito repellent, but with no more than 30 percent DEET. Do not use repellent on infants, the department says.

In the Tiverton horse case, DEM’s Division of Agriculture was notified last Monday that the horse had been displaying neurological symptoms of EEE for about 18 hours. DEM’s state veterinarian, Scott Marshall, DVM, euthanized the comatose animal and submitted samples to the HEALTH Laboratory for analysis. The specimen tested negative for rabies. The 2-year-old horse had not been properly vaccinated against EEE.

According to the DEM, the most common signs of viral encephalitis in horses are depression, stumbling, poor coordination, hind limb weakness, partial paralysis and muscle twitching. Fever can occur but is not present in all cases. These symptoms can occur in many equine diseases and should be reported to a veterinarian as soon as they are noticed so that a quick and accurate diagnosis can be made.

Mosquitoes are trapped every week statewide by DEM staff and tested at the R.I. Department of Health (HEALTH) laboratory. DEM will normally report mosquito test results once a week on a routine basis, with additional reports as necessary. Test results from mosquitoes trapped this week will be included in next week's announcement. Positive mosquito test results will generally trigger additional trapping to assess risk. This year, to date in Rhode Island, two mosquito pools have tested positive for West Nile Virus, and two mosquito pools have tested positive for EEE. West Nile Virus and EEE have been found in mosquito samples in New England states, including Massachusetts and Connecticut.

For online information about mosquito-borne diseases, go to DEM's Web site at www.dem.ri.gov, and click on “Public Health Updates,” or go to the HEALTH Web site at www.health.ri.gov, and click on “E” (Eastern Equine Encephalitis) or “W” (West Nile Virus) under “Health Topics.”