[updated with aerial spraying in Westerly, Hopkinton and Charlestown]
WESTERLY — Samples taken last week from mosquitoes trapped at Chapman Swamp returned positive tests for both Eastern Equine Encephalitis and West Nile Virus.
The state departments of Environmental Management and Health announced Tuesday that the latest round of trapping on Sept. 3, which included 116 samples from 28 locations across the state, led to the fifth positive test for EEE and second for West Nile Virus in Rhode Island this year. Both positive results came from mosquitoes trapped at Chapman Swamp, according to DEM spokesman Michael Healey.
EEE has been detected in five mosquito pools this year: two in Central Falls and three in Westerly, and West Nile Virus has been detected in Tiverton and Westerly. On Aug. 29, DEM also confirmed EEE in a horse in Westerly; the horse was euthanized. Mosquitoes carrying the EEE virus have previously been found in Chapman Swamp in 1996, 2003, 2013, and 2016.
Healey said that Rhode Island was nearing completion of aerial spraying to kill adult mosquitoes in four areas assessed to be at critical risk for the EEE virus. He also noted that Massachusetts had announced additional aerial spraying in 78 communities assessed to be at critical and high risk for the disease.
Parts of Westerly, Hopkinton and Charlestown have been identified as “critical risk communities” and were sprayed Tuesday night as part of the abatement effort. Sunday’s efforts in the region were canceled after temperatures dropped below 58 degrees and DEM officials postponed a Monday night aerial spraying of insecticide for mosquitoes because of ground fog.
Tuesday’s spraying began shortly after 7 p.m. and the plan was to make 61 short runs over parts of the three towns covering 24,994 acres, Healey said. The product being sprayed, Anvil 10+10, is extensively used in both ground-level and aerial spraying in the U.S. to control mosquitoes.
According to a news release from the town, “While spraying is occurring, it is best to err on the side of caution and limit time outdoors, bring any pets inside and keep your windows closed. The product being sprayed is being used at very low concentrations. No adverse health risks are expected with its use for mosquito control. However, it is generally good for people to limit their exposure to pesticides.”
Spraying won’t be performed over bodies of water and other sensitive areas, state officials said.
The state’s first human case of EEE since 2010 was reported last month, in an unidentified West Warwick resident. The person died Sunday, the health department announced. The case was the state’s first EEE fatality since 2007.
For more information, call 2-1-1 or visit the DEM website at www.dem.ri.gov/mosquito.
— Jason Vallee