Mosquito Borne Disease

Mosquito Borne Diseases are rare but can be serious or even fatal. Each summer, the Connecticut Agricultural Experiment Station’s Mosquito Management Program collects mosquitoes from all over the state and tests them for different diseases. There are trapping stations in every municipality within LLHD (New London and Waterford have a shared one, right on the town line).

As of September 30, 2004, mosquitoes collected in East Lyme, Groton, North Stonington and Stonington have tested positive for West Nile Virus and mosquitoes collected in Groton, Ledyard, Lyme, North Stonington and Stonington have tested positive for Eastern Equine Encephalitis. There has been one human case of West Nile Virus and have been no human or horse cases of Eastern Equine Encephalitis identified to date for this year.

There are steps you can take to reduce the presence of mosquitoes on your property – mainly reducing standing water. Even a little bit of standing water – that might accumulate in the saucer of a plant pot after a rainstorm – can be an active breeding ground for mosquitoes.  Other places that could be good mosquito breeding grounds include:

• Discarded tires
• Rain barrels, buckets
• Abandoned boats
• Clogged roof gutters
• Bird baths
• Abandoned or untreated swimming pools, wading pools
• Ceramic pots, empty cans
• Wheelbarrows
• Anywhere water can collect!

Section 19-13-B31 of the Connecticut Public Health Code states that “no person shall maintain or permit to be maintained any pond, cesspool, well, cistern, rain barrel or other receptacle containing water or accumulation of stagnant water in such a condition that mosquitoes may breed therein or may injure health or cause offense to other persons”.

If you need assistance or advice treating standing water on your property, a member of our Environmental Health staff can help. An Environmental Technician will visit your property and provide education on how to prevent and eliminate mosquitoes. Contact Patti Myers at (860) 434-1605 ext. 214 for more information.

Some things you can do to avoid mosquito bites include:

• Minimizing time outdoors at dusk and dawn.
• Ensuring door and window screens are tight-fitting and in good repair.
• Wearing 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.
• Using mosquito netting when sleeping outdoors.
• Using mosquito repellent containing an EPA-registered active ingredient when it is necessary to be outdoors. EPA-registered ingredients include DEET, Picaridin, IR3535, oil of lemon eucalyptus, para-menthane-diol (PMD), or 2-undecanone. EPA registration of skin-applied repellent products indicates that they have been evaluated and approved for human safety and effectiveness when applied according to instructions on the label.
• Wearing clothing and gear treated with permethrin. Permethrin is an insecticide that kills or repels mosquitoes and ticks.
• Covering strollers and baby carriers with mosquito nets when outside.
• Using tents or mosquito nettings when sleeping outdoors. Treat camping gear with permethrin when possible.

West Nile Virus

West Nile Virus (WNV) is a rare mosquito-borne viral infection. Most people infected with the virus experience no symptoms; however, the disease may be serious or even fatal. Certain populations such as the very young, the elderly and the immune-compromised may be a special risk. In some individuals, the virus affects the central nervous system – the brain and spinal cord. The onset of symptoms generally occurs 3 to 14 days following the bite of an infected mosquito. Symptoms may range from a slight fever, headache, body aches, rash, nausea, and swollen lymph nodes to the rapid onset of severe headache, high fever, stiff neck, disorientation, muscle weakness, coma, and, rarely, death. There is no vaccine, or cure for WNV, though treatment can reduce the severity of the symptoms.

Eastern Equine Encephalitis

Eastern Equine Encephalitis (EEE) is a rare but serious disease caused by a virus that is transmitted by mosquitoes. On average, there are five cases each year in the United States. In 2013, there was one reported human case of EEE in Connecticut. In 2019, Connecticut had four human cases of EEE, three of which were fatal.

The virus responsible for EEE attacks the central nervous system of its host. Horses are particularly susceptible to the infection and mortality rates approach 100%. Onset is abrupt and horse cases are almost always fatal. Signs of the disease in horses include unsteadiness, erratic behavior, loss of coordination, and seizures. There is no effective treatment and death can occur within 48 to 72 hours of the horse’s first indications of illness. Horses can and should be inoculated against this disease, especially in areas where EEE is known to circulate.

In humans, symptoms of EEE appear from three to 10 days after being bitten by an infected mosquito. Some infected people may not develop the illness. For those who become ill, the clinical symptoms may include high fever (103 to 106 degrees F), stiff neck, headache, and lack of energy. Inflammation of the brain, encephalitis, is the most dangerous. The disease gets worse quickly and some patients go into a coma within a week. Once symptoms develop, treatment for EEE is supportive and aimed at reducing the severity of the symptoms. As many as one-third of people who get the disease die from it and, of those who survive, approximately one-half will have permanent neurological damage. Presently, there is no available vaccine for use in humans.

Jamestown Canyon Virus

Jamestown Canyon Virus is a mosquito-borne viral infection that is circulated between mammalian-biting mosquitoes and white-tailed deer. Human cases are rare but have been increasing in the northeast and northcentral U.S. Most people infected with the virus experience no symptoms. Symptomatic infections range from mild (flu-like, fever, headache, fatigue) to severe (meningitis, encephalitis).

Highlands J Virus

Highlands J Virus in mosquitoes is being monitored by the Mosquito Management Program and has been identified in mosquitoes trapped in our area as of 2024. Highlands J Virus is not known to cause disease in humans.