Rain Boosts Mosquito Bite Illness Risk

PROVIDENCE, RI – State agencies report no recent signs of mosquito bite illness risk of West Nile Virus (WNV) or Eastern Equine Encephalitis (EEE), but recent rain is expected to change that.

On Tuesday, the Department of Environmental Management (DEM) announced recent mosquito testing by Rhode Island Department of Health (RIDOH) State Health Laboratories found no cases of either WNV or EEE. DEM collected 87 samples of mosquitoes from 37 traps set statewide during the week of Aug. 14. Results from mosquitoes collected during the week of Aug. 22 are pending, according to the DEM’s announcement.

To date, Connecticut has reported 114 positive WNV samples but no WNV human or animal cases, and no EEE in mosquitoes, humans, or animals. Massachusetts reports 54 positive WNV samples and one human case and no EEE in mosquitoes, humans, or animals.

However, recent rain is expected to cause dormant mosquito eggs to hatch, so numbers of the Asian tiger mosquito will rise. This species became prevalent in Rhode Island urban environments in 2021. It is notable as a daytime biter encountered in shaded backyards.

It has a striking black and white pattern evident to the naked eye. It develops from eggs laid in artificial containers, so residents are urged to remove standing water from containers such as buckets, pots, wheelbarrows, boats, and pools. Clogged rain gutters and puddles formed on tarps also can support the larvae of this species. The Asian tiger mosquito is known to transmit several diseases, including WNV.

Pre-pandemic, mosquito populations carrying the diseases were considered numerous enough to warrant aerial spraying, but so far, that has not  been the case  in recent  years.

Protect yourself  from Mosquito bites

• Put screens on windows and doors. Fix screens that are loose or have holes.
• At sunrise and sundown (when mosquitoes that carry EEE 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.
• 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.
• 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.
• Put mosquito netting over playpens and baby carriages.

Get rid of mosquito breeding grounds

• 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.
• Clean your gutters and downspouts so that they can drain properly.
• 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.
• Remove or treat any shallow water that can accumulate on top of a pool cover. Larvicide treatments, such asMosquito Dunks can be applied to kill immature mosquitoes. This environmentally-friendly product is available at many hardware and garden stores and on-line.
• Change the water in birdbaths at least two times a week and rinse out birdbaths once a week.

Best mosquito 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:

• Remove or cover areas where standing water can collect.
• Avoid putting animals outside at dawn, dusk, or during the night when mosquitoes are most active.
• Insect-proof facilities where possible and use approved repellents frequently.
• 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.

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.