Bad bugs
The Department of Environmental Management (DEM) and Rhode Island Department of Health (RIDOH) are announcing that the first set of mosquito samples of the 2024 season tested by the Rhode Island State Health Laboratories (RISHL) have confirmed the first two detections of Eastern Equine Encephalitis (EEE) virus in the state in 2024. The mosquito samples testing positive for EEE virus were collected in Tiverton and Coventry on June 10.
These
positive findings of EEE virus are notable because they were detected earlier
in the mosquito season than usual, indicating that EEE virus is present in the
environment in two geographically distant municipalities.
All
other samples tested negative for West Nile Virus (WNV), EEE virus, or
Jamestown Canyon Virus (JCV). These results are from the 104 mosquito samples
collected from 20 traps set statewide by DEM on June 3 and 10.
To
date, neither the Commonwealth of Massachusetts or State of Connecticut have
reported any EEE virus, WNV, or JCV findings. The 2023 mosquito season was a
higher-than-average risk year for mosquito-borne disease in southern New
England.
Although
extremely rare in humans, EEE virus is very serious and has a much higher human
mortality rate than WNV. Approximately 30% of people with EEE virus die and
many survivors have ongoing neurological problems. Unlike WNV, which is
prevalent in Rhode Island every year, EEE virus risk is variable, changing from
year to year.
With continued trapping and testing, DEM and RIDOH will be able to assess the EEE virus risk level this mosquito season. For more information on EEE virus and ways to prevent it, please visit www.health.ri.gov/eee.
WNV is
the leading cause of mosquito-borne disease in the continental United States
and is much more prevalent than EEE virus. Cases of WNV occur during mosquito
season, which starts in the summer and continues through fall. There are no
vaccines to prevent or medications to treat WNV in people.
Fortunately,
most people infected with WNV do not feel sick. About one in five people who
are infected develop a fever and other symptoms. About one out of 150 infected
people develop a serious, sometimes fatal, illness. For more information about
WNV, please visit www.health.ri.gov/wnv.
EEE
virus and WNV are typically present in wild bird populations. Birds are
reservoirs of the diseases and mosquitoes transmit these viruses among birds.
During an active mosquito season, the viruses are amplified in the environment
with each generation of mosquitoes.
At a
certain point, several mosquito species that bite both birds and mammals serve
as a bridge between infected birds and uninfected mammals. Most bridge
species are within the Aedes, Coquillettidia, and Culex genera.
The
testing of mosquito samples for JCV is new for Rhode Island due to a new
Polymerase Chain Reaction (PCR) testing method, but the virus is not new to the region. JCV is a mosquito-borne pathogen that
circulates widely in North America, primarily between deer and mosquitoes, but
can also infect humans. Human cases can occur from late spring through mid-fall
and is most common early and late in the mosquito season with cooler weather.
Four
human JCV cases have been reported in Rhode Island residents since 2013. People
can be infected and not develop any symptoms, or only develop very mild
symptoms. Early symptoms can include fever, muscle aches, headaches, and
fatigue. Rarely, more serious central nervous system disease, including
meningitis or encephalitis, can occur. There are no vaccines to prevent or
medicines to treat JCV.
Local communities voluntarily participate with mosquito control through DEM’s larvicide distribution program, which provides municipalities with a limited free supply of mosquito larvicide briquettes that release environmentally-benign bacteria over a 90-day period in underground stormwater catchment basins that are prime breeding areas of mosquitoes, requiring only one application per season.
In
April, the Town of Westerly conducted an aerial application of mosquito larvicide across
500 acres of Chapman Swamp and nearby swamplands by helicopter
recommended as part of the state's action plan to reduce mosquito populations
and related disease risk.
Mosquito Control:
Residents
can help control mosquitoes by removing backyard mosquito breeding grounds. The
Asian Tiger Mosquito has become prevalent in Rhode Island urban environments,
and it is expected to be common again this season. 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.
Rhode
Islanders should take the following measures 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 carrying EEE virus
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
Do not use bug spray with DEET on infants under two months
of age. Check the product label to find the concentration of DEET in a product.
The American Academy of Pediatrics recommends that repellents should contain no
more than 30% DEET when used on children. 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.
Remove mosquito breeding grounds!
o
Remove items around your house and yard that collect 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 online.
o
Clean and change water in birdbaths at least once a week.
Best practices for horse owners!
Horses
are particularly susceptible to WNV and EEE virus. 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 signs 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 health.ri.gov/mosquito for additional
mosquito prevention tips, videos, and local data. Mosquitoes are trapped weekly
by DEM and tested at the RIDOH State Health Laboratories. DEM issues advisories
on test results from June through September, with additional reports as
necessary. Typically, positive test results trigger additional trapping to
assess risk.
For
more information on DEM programs and initiatives, visit www.dem.ri.gov.
Follow DEM on Facebook, Twitter (@RhodeIslandDEM), or
Instagram (@rhodeisland.dem) for timely updates.