Eastern Equine Encephalitis Virus: What You Need to Know

Although not talked about as much as other mosquito-borne diseases, the Eastern Equine Encephalitis virus (EEEV) is one of the most serious and deadly diseases transmitted by a mosquito. When infected, symptoms occur between four and ten days after contracting the disease and begin with headache, vomiting, chills and fever. EEEV often ends with severe brain damage, seizures or coma. Since there is no specific treatment, cure, or vaccine, the severity of this disease is extremely high. According to the Center for Disease Control and Prevention, approximately 35% of humans who develop EEEV die, representing the highest mortality rate among arboviruses. Many of those who survive will have mild to severe permanent neurologic damage.

Eastern Equine Encephalitis Virus is the most severe mosquito-transmitted disease in the U.S. with a 33% mortality rate among people that display symptoms.

There were 82 human cases of EEEV reported between the years 2004-2013. The Eastern Equine Encephalitis Virus has been reported mostly in the Atlantic and Gulf Coast states and according to the CDC, it occurs primarily from late spring through early fall. This rare disease is carried by the Aedes, Coquillettidia and the Culex mosquito species. These mosquitoes are usually found around freshwater hardwood swamps, with the most human cases reported in Massachusetts (24 EEEV cases) and Florida (15 EEEV cases).

 Eastern Equine Encephalitis Virus is typically found in the Eastern United States (as far west as Michigan) and in the south along the Gulf Coast.

The disease is significantly more severe among horses, where the mortality rate may be as high as 90%. It is also more prevalent in horses, with 607 confirmed equine cases occurring in the United States between 2012 and 2015. A vaccine does exist to prevent the disease among horses, and it is typically recommended by veterinarians. Experts also recommend horse owners change the water in troughs at least twice a week to prevent mosquito breeding.

Eastern Equine Encephalitis Virus transmission.
 Eastern Equine Encephalitis Virus is thought to confer lifelong immunity against reinfection.

The only way to prevent EEEV among humans is to not get bitten by an infected mosquito. Since there is no known cure or treatment, bite prevention is essential.

Effective bite prevention begins with limiting potential breeding sites for mosquitoes, primarily by removing standing water wherever possible. Every effort should be made to eliminate standing water in buckets, old tires, gutters, birdbaths, flower pots and more. Additional protection inside the home includes the use of air conditioning and properly maintained window screens. For time spent outdoors, experts recommend use of mosquito repellents containing DEET and loose fitting clothing. More mosquito prevention tips for homeowners can be found at mosquito-awareness.com.

For mosquito abatement professionals, the key to control is to establish an integrated mosquito management (IMM) approach that includes surveillance of breeding sites and the early use of larvicides for prevention as well as the use of adulticides to address problem adult mosquito populations. IMM is designed to attack mosquitoes at each stage of their life cycle. No two mosquito habitats are alike – and neither are the ways they need to be treated. The mosquito products from Central Life Sciences provide solutions for both easy-to-access and difficult-to-treat areas.

For the most efficient control of Culex mosquitoes, larvicides should be proactively administered to known breeding sites. Altosid® larvicides are available in multiple formulations containing (S)-methoprene, an insect growth regulator (IGR) that stops mosquitoes from becoming breeding, biting adults. For an alternate approach, FourStar® Microbials feature a larvicide that kills mosquito larvae before they become adults by using the naturally occurring bacteria Bacillus sphaericus (Bsph) and Bacillus thuringiensis israelensis (Bti).

For the remaining adult populations, adulticides kill the fully developed mosquitoes that spread diseases and offer the quickest approach to reduce the size of mosquito populations. Zenivex® adulticides feature Etofenprox, and they are classified as reduced risk by the EPA.

Eastern Equine Encephalitis virus and other mosquito-borne diseases can be a threat to public health, but one that can be minimized through effective vector control efforts. To learn more about mosquito control, contact Senior Field Technical Service Manager Mel Whitson at 321-480-0478 or mwhitson@central.com or find your local sales representative.