public health

Eastern Equine Encephalitis Rarely Documented in Wild Mammals; DEEP and DPH Advise Continued Precautions to Avoid Mosquitoes

The Connecticut Department of Energy and Environmental Protection (DEEP) today announced that a white-tailed deer that exhibited neurologic symptoms and died on August 12, 2024, in Lisbon, Connecticut, was infected with the eastern equine encephalitis (EEE) virus.

EEE is a serious but rare illness caused by a virus that is transmitted by mosquitoes. It is the most severe mosquito-transmitted disease in the U.S., with approximately 40 percent mortality and significant brain damage in half of survivors. No human or horse cases of EEE have been reported in Connecticut this year, although human cases have been documented in Massachusetts, Vermont, and New Jersey.

The CT Veterinary Medical Diagnostic Laboratory at the University of Connecticut (UCONN) conducted a necropsy and tested the deer for various diseases, including rabies, hemorrhagic disease, West Nile virus (WNV), and EEE, and determined that the EEE virus caused the deer’s neurologic symptoms.

This finding is rare in wild mammals but is not surprising since EEE-positive mosquitoes have been documented by the Connecticut Agricultural Experiment Station (CAES) in nearby towns. However, this finding also indicates that the EEE virus is present in mammal-biting mosquitoes, prompting Connecticut’s Mosquito Management Program to continue to advise residents to take proper precautions to protect themselves from mosquito bites, such as wearing mosquito repellent and covering bare skin, especially during dusk and dawn when mosquitoes are most active.

“DEEP urges residents to continue to take appropriate precautions to avoid contact with mosquitoes,” said DEEP Commissioner Katie Dykes. “With EEE now detected in mammal-biting mosquitoes in Eastern Connecticut, residents should continue to be vigilant when taking part in outdoor activities to avoid exposure to mosquito bites.”

“Infection with EEE virus can cause serious illness affecting the brain. Symptoms include high fever, headache, stiff neck, and decreased consciousness,” said Department of Public Health (DPH) Commissioner Manisha Juthani, MD. “The disease is fatal in 25-50 percent of cases and many of those who recover experience lasting health problems. Individuals with symptoms suggestive of EEE infection should contact their physician immediately. No human vaccine against EEE virus infection or specific antiviral treatment for clinical EEE virus infections is available.”

The CAES maintains a network of 108 mosquito-trapping stations in 88 municipalities throughout the state to test mosquitoes for various pathogens, including EEE and WNV. So far this season, WNV-positive mosquitoes have been found in 31 towns and EEE-positive mosquitoes have been detected in 5 eastern Connecticut towns: Canterbury, Ledyard, North Stonington, Sterling, and Voluntown. Positive findings are reported to local health departments and on the CAES website.

To reduce the risk of being bitten by mosquitoes, residents should take the following personal precautions:

• Minimize time spent outdoors when mosquitoes are most active, especially dawn and dusk.
• Consider the use of mosquito repellents containing an EPA-registered active ingredient, including DEET, Picaridin, IR3535, oil of lemon eucalyptus, para-methane-diol (PMD), or 2-undecanone when it is necessary to be outdoors.
• After returning indoors, wash any treated skin with soap and water.
• Wear shoes, socks, long pants, and a long-sleeved shirt when outdoors for long periods of time, or when mosquitoes are more active. Clothing should be light-colored and loose-fitting and made of tightly woven materials that keep mosquitoes away from the skin.
• Use mosquito netting when sleeping outdoors or in an unscreened structure and to protect infants when outdoors.

Residents are also encouraged to take steps at home to protect against mosquitoes, such as making sure door and window screens are tight-fitting and in good repair, and not letting stagnant water collect around your home. Dump water out of old tires, wheelbarrows, and wading pools. More information on mosquito control around the home can be found on the Connecticut Mosquito Management Program website.

Late summer and early fall is a popular time to enjoy the wide variety of outdoor recreation opportunities here in Connecticut – such as hiking, camping, fishing, birdwatching, boating or hunting. Anyone enjoying the outdoors in Connecticut should protect themselves against mosquito bites while out in the field.

Fall hunting seasons start soon and extend over the next few months in Connecticut, including the archery deer and turkey season, which opens in mid-September. The EEE virus cannot by contracted by people who eat the meat of harvested animals, although, as with all wild game, the meat should be prepared properly and cooked to the proper temperature.

The response to mosquito transmitted diseases in Connecticut is a collaborative inter-agency effort involving DEEP, CAES, DPH, the Department of Agriculture, and the Department of Pathobiology at UCONN. These agencies are responsible for monitoring mosquito populations and the potential public health threat of mosquito-borne diseases.

For information on WNV and EEE, what can be done to prevent getting bitten by mosquitoes, the latest mosquito test results, and human infections, visit the Connecticut Mosquito Management Program website.