EEE Found in Maryland Mosquitoes

Maryland's first Eastern equine encephalitis (EEE) virus positive mosquito sample since 2004 has been confirmed. The mosquitoes were collected from the Pocomoke River swamp in northern Worcester County.

The virus was detected in a pool of Culiseta melanura or "dark swamp mosquitoes," a species rarely found outside of its swamp habitat. The dark swamp mosquito feeds primarily on birds. The Pocomoke swamp is the area of Maryland where EEE is most frequently found due to the high number of mosquitoes and a high population of breeding and migratory birds.

"We have known that EEE is active on the Lower Eastern Shore of Maryland for years and conduct active surveillance to detect its presence," said Maryland Department of Agriculture Mosquito Control Chief Cyrus Lesser. "The presence of EEE in mosquitoes increases the importance for people to take precautions to prevent mosquito bites. The

Maryland Department of Agriculture will continue to monitor mosquito populations in the lower Eastern Shore region and increase mosquito control measures through September."

EEE is spread only by the bite of an infected mosquito and can cause a swelling of the brain (encephalitis). The disease in humans and other animals is rare but can occur when an infected mosquito takes a blood meal. EEE disease occurs primarily in rural areas close to swamps and marshes with high mosquito populations.

Humans, equine and ratites (flightless birds such as ostriches and emus) can contract the virus. Clinical signs of EEE in horses and ratites include apprehension, depression, listlessness, paralysis, lack of coordination, weakness, head-pressing, circling, and stumbling. These symptoms are not exclusive to EEE, so it is important to seek professional veterinary diagnosis immediately if any of the signs are present.

Although EEE tends to occur in humans less frequently than West Nile virus (WNV), it can be far more devastating. Up to 50% of EEE infected persons who develop neurological symptoms may die compared to fewer than 10% who die following WNV neurological illness. Many EEE survivors have long-term neurological damage.

Typical symptoms of EEE in humans include fever, headache, mental confusion, vomiting, extreme tiredness, muscle aches, 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 for use in people. There are however, effective vaccines against both viruses for horses and ratites, and owners are encouraged to get their animals vaccinated and boostered in a timely manner in consultation with their veterinarian.

The last reported human case of EEE in Maryland was in 1989. Two equine cases of EEE in Maryland were confirmed on July 28, 2003, for the first time since 1996. The human and equine cases occurred on the Lower Eastern Shore. This is the second occurrence of mosquito-born virus in Worcester County in 2007. The first was a probable human case of WNV illness reported in August.

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