EEE is spread by the bite of an infected mosquito and can cause a swelling of the brain (encephalitis). The disease is rare in humans, but can occur when an infected mosquito bites a person. EEE disease occurs primarily in areas close to swamps and marshes with high mosquito populations. The last confirmed human case in Maryland was in 1989, and prior to that there were two cases in 1982. The last confirmed case in a horse in Maryland was in 2009 in Wicomico County.
Although EEE occurs in humans less frequently than West Nile virus (WNV), it can be more serious. Only a subset of people infected with either virus develop neurological illness, however of those who develop neurological illness, approximately one-third of all EEE-infected persons may die compared to fewer than 10 percent who die following WNV neurological illness. EEE survivors can have long-term damage to the nervous system.
Typical symptoms of EEE in humans include fever, headache, mental confusion, nausea, vomiting, muscle aches, joint pain, and sometimes seizures and coma. Individuals reporting these symptoms should be referred to their health care provider. Symptoms usually occur four to 10 days after exposure to a mosquito carrying the virus. There is neither a specific treatment nor a vaccine available for use in humans infected with EEE virus.
In horses, EEE is a serious disease that can be fatal; however, well vaccinated horses are generally safe from the disease. The Maryland Department of Agriculture (MDA) encourages all horse owners to consult with their veterinarian to discuss the best vaccination program for their horse and its circumstances. The horse in Worcester County had not been vaccinated. Infected horses show a range of clinical signs that often progress over two to three days, including depression, altered mental status, circling, problems with balance, weakness, aimless wandering, impaired vision, walking (gait) abnormalities, head pressing, paralysis, convulsions and death. Horses that survive serious disease often have permanent nervous system deficits.
MDA, working with Worcester County officials, has mapped out a 6,000 acre area in the Whaleyville area where air spraying for mosquitoes will be conducted tonight, beginning at 5 p.m. .
MDA generally checks mosquito populations in the area every week and conducts ground spraying according to its findings. As a result of the EEE discovery, MDA will increase ground spraying activities to approximately every 5 to 7 days over the next two weeks. Spraying will take place between dusk and dawn.
Measures people can take to protect themselves from diseases spread by mosquitoes include:
- Avoid areas of high mosquito activity
- Avoid unnecessary outdoor activities at dawn and dusk when mosquitoes are most active
- Wear long pants, long-sleeved shirts and hats to reduce mosquito exposure
- Use an EPA-registered insect repellent according to package directions
For additional information on West Nile virus and other mosquito-borne viruses, visit:
- Maryland Department of Health and Mental Hygiene: http://phpa.dhmh.maryland.gov/OIDEOR/CZVBD/SitePages/west-nile.aspx
- Maryland Department of Agriculture: http://mda.maryland.gov/plants-pests/Pages/mosquito_control.aspx
- Centers for Disease Control and Prevention: http://www.cdc.gov/westnile/index.html and http://www.cdc.gov/easternequineencephalitis/
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