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Mosquito Advisory: State Confirms Fourth Positive Finding Of Eastern Equine Encephalitis And First West Nile Virus Detection In Latest Round Of Mosquito Trapping

In response to the elevated risk of mosquito-borne disease, the state has begun trapping in five new communities since last week bringing to 23 the number of municipalities where trapping now is being conducted and is scheduled to begin aerial larvicide applications at Chapman Swamp in Westerly on Thursday, weather permitting.

PROVIDENCE The Department of Environmental Management (DEM) and the Rhode Island Department of Health (RIDOH) today announced that a second mosquito sample trapped at Chapman Swamp in Westerly tested positive for Eastern Equine Encephalitis (EEE). The agencies also confirmed that mosquitoes trapped in Tiverton became the first sample to test positive for West Nile Virus (WNV) in Rhode Island in 2019. With the latest trapping and testing results, there have now been four EEE detections two in Central Falls and two in Westerly and one WNV detection statewide to date. On August 29, DEM confirmed EEE in a horse in Westerly. The following day, RIDOH confirmed the first human case of EEE in West Warwick.

Last week DEM and RIDOH, supported by the Rhode Island Emergency Management Agency (RIEMA), announced that the state would ramp up mosquito testing, control, and outreach measures. Since the last round of trapping on August 26, DEM has added 10 new traps in five new communities and now is trapping at 38 locations in 23 municipalities. RIDOH's State Health Laboratories worked over this past weekend to test the mosquitoes and expedite testing results. RIEMA continues to coordinate communications between state government and the state's 39 cities and towns. By increasing trapping and tracking mosquito species, volume, and infection, the state is working to assess the risk of further human disease.

In the latest round of trapping, DEM collected 123 pools, or samples, from 28 traps August 26. The mosquitoes testing positive for WNV came from a trap set in Tiverton. DEM has trapped WNV-positive mosquitoes from this same location in previous years. The second EEE-positive mosquito sample was trapped in Westerly from the same trap in Chapman Swamp that produced an EEE-positive mosquito detection on August 19. DEM has trapped two species of mosquitoes that have tested positive for EEE at Chapman swamp this year. Mosquitoes carrying the EEE virus have previously been found in Chapman Swamp in 1996, 2003, 2013, and 2016.

With the input of public health experts at RIDOH and entomology experts at the University of Rhode Island, DEM traps mosquitoes at locations throughout Rhode Island from early June to late September annually. DEM places the traps strategically based on knowledge of the environmental conditions conducive to EEE and WNV amplification in the mosquito population. Typically, DEM sets between 25 and 30 traps in Westerly, Charlestown, South Kingstown, North Kingstown, Exeter, Warwick, Cranston, Johnston, Providence, Central Falls, Pawtucket, East Providence, Barrington, Warren, Bristol, Tiverton, Portsmouth, and Newport.

Since the last round of trapping on August 26, DEM has added traps in West Warwick, where the state's first human case of EEE originated; West Greenwich, near the state line with southeastern Connecticut where there have been numerous EEE detections in mosquitoes and two cases of EEE virus infection reported in horses; and Burrillville, North Smithfield, and Cumberland. These towns border several Worcester County communities that Massachusetts public health officials have identified as areas of high risk.

The latest trapping detections of mosquito disease reaffirm the need for aerial spraying, and as announced on August 30, the state is taking all necessary preparations for conducting spraying to kill both larval and adult mosquitoes. RIDOH and DEM are actively evaluating options and will continue to provide updates. Spraying affects all mosquito species and reduces risks for both EEE and WNV infections. The application of larvicide designed to eliminate the larvae before they mature into adult mosquitoes could begin as early as Thursday in Chapman Swamp in Westerly, with other limited priority areas still being identified. Aerial applications of pesticides are contingent on weather conditions, which must be calm. The state will release a spraying schedule before any aerial applications to eliminate either larval or adult mosquitoes occur.

Previous recommendations from RIDOH still are in effect and are related to the prevention of both EEE and WNV. On Monday of last week, RIDOH recommended to schools and municipal leaders that games, practices, and other outdoor activities scheduled to occur during early morning or dusk hours be rescheduled to earlier in the afternoon or relocated to an indoor venue. The "smart scheduling" of events is intended to help minimize the risk of mosquito bites for players, coaches, and spectators. RIDOH recommends that smart scheduling stay in effect for the remainder of the mosquito season, which typically ends in mid-October (after the first hard frost).

In addition to following this smart scheduling recommendation, there are other measures that Rhode Islanders should take to protect themselves from mosquito bites, and to help minimize mosquito breeding.

Protect yourself

o Put screens on windows and doors. Fix screens that are loose or have holes. o At sunrise and sundown (when mosquitoes that carry EEE and WNV are most active), consider rescheduling outdoor activities that occur during evening or early morning. If you must be outside, wear long-sleeved shirts and long pants and use bug spray. o Use EPA-approved bug spray with one of the following active ingredients: DEET (20-30% strength); picaridin, IR3535; and oil of lemon eucalyptus or paramenthane. Always read the label and follow all directions and precautions. o If you plan to hike in the woods in daylight, it is advisable to wear repellent to prevent being bitten by daytime mosquitoes. o Do not use bug spray with DEET on infants under two months of age. Children should be careful not to rub their eyes after bug spray has been applied on their skin. Wash children's hands with soap and water to remove any bug spray when they return indoors. o Put mosquito netting over playpens and baby carriages.

Get rid of mosquito breeding grounds

o Get rid of anything around your house and yard that collects water. Just one cup of water can produce hundreds of mosquitoes; an unused tire containing water can produce thousands of mosquitoes. o Clean your gutters and downspouts so that they can drain properly. o Remove any water from unused swimming pools, wading pools, boats, planters, trash and recycling bins, tires, and anything else that collects water, and cover them. o Remove or treat any shallow water that can accumulate on top of a pool cover. Larvicide treatments, such as Mosquito Dunks can be applied to kill immature mosquitoes. This environmentally-friendly product is available at many hardware and garden stores and on-line. o Change the water in birdbaths at least two times a week and rinse out birdbaths once a week.

Best practices for horse owners

Horses are particularly susceptible to WNV and EEE. Horse owners are advised to vaccinate their animals early in the season and practice the following:

o Remove or cover areas where standing water can collect. o Avoid putting animals outside at dawn, dusk, or during the night when mosquitoes are most active. o Insect-proof facilities where possible and use approved repellents frequently. o Monitor animals for symptoms of fever and/or neurological signs (such as stumbling, moodiness, loss of appetite) and report all suspicious cases to a veterinarian immediately. If you are unsure if your horse is properly vaccinated, you should consult with your veterinarian.

For more information about DEM divisions and programs, visit www.dem.ri.gov. Follow us on Facebook at www.facebook.com/RhodeIslandDEM or on Twitter (@RhodeIslandDEM) for timely updates.

Visit http://www.health.ri.gov/mosquito for additional mosquito prevention tips, videos, and local data. For more information about DEM divisions and programs, visit www.dem.ri.gov. Follow us on Facebook at www.facebook.com/RhodeIslandDEM or on Twitter (@RhodeIslandDEM) for timely updates.

Related links

  • Department or agency: Department of Environmental Management
  • Online: http://www.dem.ri.gov/
  • Release date: 09-03-2019

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