2009-06-04 / News

Take precautions to avoid mosquito-born illness

As mosquito season approaches, and with West Nile Virus and Eastern Equine Encephalitis so firmly established throughout the state, the Department of Environmental Management and the Department of 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 will distribute the larvicide Altosid, as well as Bacillus sphaericus, a naturally derived bacterium, to municipalities for treating all public area catch basins. DEM will trap mosquitoes on a weekly basis throughout the state beginning the week of June 8. The mosquitoes will be tested at the HEALTH laboratory, and DEM will provide, at minimum, weekly updates on test results to the media, with additional reports as necessary. Positive results will generally trigger additional trapping to assess risk.

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, incoordination, stumbling and neurological signs; and report all suspicious cases to a veterinarian immediately.

2008 roundup

Last year, in Rhode Island, nine mosquito pools trapped in Providence, Pawtucket, Central Falls and Westerly and tested at the RI Department of Health laboratory were confirmed positive for West Nile Virus. However, no mosquitoes in Rhode Island tested positive last year for Eastern Equine Encephalitis.

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 birdbiting 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 to 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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