Insect Shield Shares Eastern Equine Encephalitis Overview, Risks and Protection Methods

A rare and lethal mosquito-borne illness is making headlines across the country. Eastern Equine Encephalitis, otherwise known as EEE, is the most lethal of the arbo-viruses transmitted by mosquito species in the U.S. to humans, horses and other animals. Permethrin-treated clothing is an effective method of staying protected.

Mortality rates for humans are very high, ranging from 30-60%, with survivors at risk for significant neurological deficits. According to the CDC, an average of 7 human cases of EEE are reported annually in the U.S. Recently, human cases have been reported in Massachusetts and Michigan, while the virus has also been found in several horses in Massachusetts, Michigan and Connecticut. Permethrin-treated clothing is an effective method of staying protected.

EEE Impact to Humans and Animals

Eastern equine encephalitis is maintained in a cycle involving Culiseta melanura mosquitoes (primarily bird feeders and avian hosts in freshwater hardwood swamps). Transmission to humans requires mosquito species capable of creating a “bridge” between infected birds and uninfected mammals such as some Aedes, Coquillettidia, and Culex species that feed on both types of hosts such as humans and horses.

“As humans continue to move into hardwood swamps, they will come into increased contact with the bridge vectors and potential disease transmission,” explains Joe Conlon, Technical Advisor of the American Mosquito Control Association. “Fortunately, there are generally very few cases countrywide yearly, however, it only takes one case and one fatality to remind us that we must protect ourselves,” Conlon adds.

Which Mosquitoes Can Transmit EEE

When compared to other diseases such as West Nile and others, EEE is far less prevalent yet more lethal and potentially incurable. Certain mosquitoes, such as Aedes vexans, one of the most numerous human-biters, lay eggs in ground depressions that can remain viable for years, awaiting rains. Coquillettidia perturbans, which breeds in among cattail swamps is another vector, while Ochlerotatus canadensis, a woodland swamp breeder and Oc. sollicitans, which breeds in saltmarshes, also serve as vectors.

Signs and Symptoms of EEE

Symptoms of EEE generally occur a few days or up to two weeks after infection. Symptoms can include:

  • high fever
  • headache
  • Tiredness
  • nausea/vomiting
  • neck stiffness

According to Boston Children’s Hospital, the symptoms of encephalitis depend on the part of the brain that is inflamed, the amount of inflammation and the person’s age and overall health.

Some of the most common symptoms of encephalitis include:

  • seizures
  • confusion (disorientation)
  • coma

In one-third of cases, encephalitis can be fatal or lead to permanent brain damage.

Best practices for prevention

  • Keep repellents available when outside, and wear permethrin-treated clothing.
  • Fill in or drain any low places (puddles, ruts, etc.) in the yard.
  • Keep drains, ditches, and culverts free of weeds and trash so water will drain properly.
  • Keep grass cut short and shrubbery well-trimmed around the house so adult mosquitoes will not hide there.
  • Install bird or bat houses to attract these insect-eating animals has been suggested as a method of mosquito control.