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First Mosquitoes Trapped Test Negative for WNV and EEE

PROVIDENCE - The Department of Environmental Management announces test results from the first mosquitoes trapped this season. All of the 104 mosquito pools collected by DEM staff from 15 traps set statewide on June 9 have been confirmed negative for both West Nile Virus and Eastern Equine Encephalitis. Test results are pending at the RI Department of Health Laboratory for 104 mosquito pools collected from 21 traps set on June 16.

DEM will normally report mosquito test results once a week on a routine basis, with additional reports as necessary. Positive mosquito test results will generally trigger additional trapping to assess risk.

With West Nile Virus and Eastern Equine Encephalitis (EEE) established throughout the state, DEM and the Department of Health (HEALTH) are reminding Rhode Islanders that personal protection is the first line of defense against mosquito-borne diseases.

Residents should, as part of their normal seasonal routine, protect themselves from exposure to West Nile Virus and EEE by avoiding mosquito bites and eliminating mosquito breeding grounds. At this time of year, they are urged to get rid of anything in their yards that holds standing water, such as old tires, buckets, junk, and debris, and to make sure their gutters are clean so that they drain properly. Mosquitoes breed in standing water. Just one cup of standing water can produce hundreds of mosquitoes.

Personal protection and larviciding are cornerstones of the state's mosquito response protocol. Aerial or ground spraying will be recommended only when a team of mosquito-control experts determines that the public is at substantial risk of contact by infected mosquitoes.

DEM distributed the "Four Star" larvicide product, which is a briquette that releases environmentally-benign bacteria over a 90-day period, to municipalities on June 3 at East Farm at the University of Rhode Island for treating all public area catch basins. Catch basins are considered prime breeding areas of mosquitoes in both urban and suburban settings, and the use of larvicide is the best way for communities to reduce mosquito numbers and risk. Some communities will also be applying Bti "donuts" to standing water bodies and small areas that are hard to treat. Both products are specific to mosquito larvae and have excellent environmental track records.

Tips for Horse Owners Because horses are susceptible to West Nile Virus and EEE, Rhode Island horse owners should vaccinate their horses early in the season and take measures to control and prevent mosquito exposure. Those controls should include: removing or covering all areas where standing water can collect; applying mosquito larvicide in appropriate locations; and avoiding turning animals outside at dawn, dusk and during the night when mosquitoes are most active. Horse owners should insect-proof facilities where possible; use approved repellants frequently; monitor animals for symptoms of fever, in-coordination, stumbling and neurological signs; and report all suspicious cases to a veterinarian immediately.

2013 Rhode Island Roundup Last year, in Rhode Island, four isolations of EEE were found in communities across the southern part of the state including Westerly, South Kingstown, Exeter and Tiverton. Test results also confirmed seven findings of WNV in six Rhode Island communities including Providence (two positives), Charlestown, South Kingstown, Barrington, East Providence and North Kingstown. Mosquitoes were tested at the Department of Health Laboratory in Providence.

The Viruses EEE, a cyclical virus, while not nearly as common as West Nile Virus, has a higher fatality rate. It is a viral disease contracted through the bite of an infected mosquito. In most years, the virus is limited to native bird populations and bird-biting mosquitoes, but occasionally the virus can be transmitted to humans and domestic animals. EEE virus affects the brain with symptoms that appear 5 to 15 days after being bitten by an infected mosquito. Symptoms may include high fever, headache, stiff neck and decreased consciousness. Up to 50 percent of cases may result in fatality. Individuals with symptoms suggestive of EEE should contact their physician immediately.

West Nile Virus is also a mosquito-transmitted, viral disease that causes encephalitis. However, mortality rates are much lower than those of EEE. Most people bitten by WNV-infected mosquitoes do not get sick. However, the elderly and people with weakened immune systems are more prone to infections. Symptoms begin 3-15 days after the bite from an infected mosquito. Symptoms may include fever, headache, nausea, rash, stiff neck, muscle weakness, and disorientation. Of cases with serious symptoms, up to 15 percent may result in fatality. West Nile Virus made its first appearance in the Western hemisphere, in the New York City area in 1999, and has since spread throughout the country.

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  • Department or agency: Department of Environmental Management
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  • Release date: 06-23-2014

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