Eastern equine encephalitis

Eastern equine encephalitis (EEE) is a vector-borne disease that can be spread to humans or horses through the bite of an infected mosquito. In the past, EEE has mainly affected horses; however, in recent years, mosquitoes carrying the EEE virus have been identified in Ontario. To date, there have been no human cases of EEE reported in Ontario or Canada.

If someone gets EEE, the person will typically not experience any signs or symptoms. If symptoms do occur, they will often be very general and may include:

• fever
• chills
• muscle pain
• weakness

General symptoms do not involve the nervous system and can last for two weeks. Some people infected with EEE can develop a more severe form of illness called encephalitis (swelling of the brain). This type of illness is rare.

Symptoms of encephalitis can include:

• sudden onset of severe headache
• fever
• drowsiness
• loss of appetite
• vomiting
• coma

About one-third of all patients who develop encephalitis will die from the disease or suffer permanent mental and physical side effects. If you experience any of these symptoms and think you might have EEE, see your doctor right away.

EEE is a virus. There are currently no anti-viral medications available to treat humans infected with EEE. In Ontario, humans have a very low risk of becoming infected with EEE. There have been no recorded human cases of EEE in Ontario or Canada to date.

While there is no treatment for humans, a seasonal vaccination for horses is available. Horses can also be infected and die if they are bitten by a mosquito that is carrying EEE. By vaccinating horses, these animals will be protected and the hope is, as a result, there will be less spread of EEE to humans.

The transmission cycle (how the virus is passed) begins when mosquitoes feed on the blood of an infected bird. Once a mosquito bites an infected bird, it becomes infected with EEE and could possibly transmit the virus to humans or horses through a bite.

Whether you are in your backyard, exploring local trails, or vacationing, it’s important to protect yourself and your family from mosquito bites. Here’s how:

• use an insect repellent to prevent insect bites
• if possible, stay indoors from dusk to dawn when mosquitoes are most active
• wear light-coloured clothing, including long sleeves, long pants, socks, and a hat whenever you are outdoors
• check all window and door screens in your home to ensure there are no tears or holes for mosquitoes to get through

Mosquitoes need only a small amount of calm, standing water to lay their eggs and for larvae to hatch. Change or remove standing water every two to three days from areas that can hold water, including:

• bird baths
• old tires
• unused containers
• barrels
• flower pot saucers
• swimming pool covers
• wading pools
• clogged gutters and eaves troughs
• clogged drainage ditches
• small containers like cans or bottle tops
• unused children’s toys or vehicles

Public Health Sudbury & Districts is trapping mosquitoes to identify the different species of mosquitoes that are present in the Sudbury and Manitoulin districts and to find out if the mosquitoes are carrying viruses such as Eastern Equine Encephalitis and West Nile viruses. This is called surveillance.

Staff from Public Health Sudbury & Districts are doing the mosquito trapping. Trapping begins at the beginning of the mosquito season and continues until the end of the season. Traps are set up throughout the Sudbury and Manitoulin districts. If you come across a trap, please do not tamper with it. It is important that mosquito traps be left undisturbed so that the surveillance is accurate

Only certain species of mosquitoes feed on birds. Therefore, it is possible to find the Eastern Equine Encephalitis and the West Nile viruses in those mosquitoes. Mosquitoes caught in the traps will be tested to identify their species and to find out if they are carriers of either Eastern Equine Encephalitis virus or West Nile virus. This information will help Public Health Sudbury & Districts inform the public about the risk of infection.

For more information, call Public Health Sudbury & Districts at 705.522.9200 (toll-free 1.866.522.9200).