Eastern / Western Equine Encephalomyelitis

Eastern / Western Equine Encephalomyelitis


Encephalomyelitis on its own means inflammation of the brain and spinal cord.  Eastern Equine Encephalomyelitis (EEE) and Western Equine Encephalomyelitis (WEE) are viruses that are spread by mosquitos.  The reservoir for the disease is actually birds and mice, but it is spread by mosquito bite.  Humans are also susceptible to the disease when bitten by an infected mosquito, but people rarely contract the disease from horses because horses do not shed enough virus to be contagious.


If your horse contracts EEE they develop an acute fever, depression, loss of appetite and stiffness in their body.  As the disease progresses over the course of a few weeks symptoms become more severe and your horse will show confusion, excitability, trembling and other neurological symptoms such as head tilt, loss of vision, stumbling and eventually paralysis.  Horses with advanced EEE usually press their head against a wall to ease internal pressure.  The mortality rate off EEE is very high; 75 – 100% of horses with EEE do not survive.  Paralysis progresses and the infected horse will eventually lose function in its limbs and organs.  The whole cycle happens very quickly in just a few weeks.  Horses that do recover usually have irreversible neurological damage.  WEE starts out with similarly, with fever and stiffness, but the horse is more likely to fight it off and recover.


Both of these diseases are preventable with EEE/WEE vaccines.  Most boarding stables and competition associations require proof of vacation to bring your horse on the premises to reduce occurrence of this terrible disease.  Mosquito control is another good way to help reduce your horses’ chances of contracting EEE.  Bug sprays, fly sheets, fans, and avoidance of standing water will all help keep mosquitos away from you and your horse.





Comparative Study of the pathological effects of western equine encephalomyelitis virus in four strains of culex tarsalis coquillett (diptera: culicidae).


Risk of exposure to eastern equine encephalomyelitis virus increases with the density of northern cardinals.


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Eastern equine encephalitis in Latin America.


Natural variation in the heparin sulfate binding domain of the eastern equine encephalitis virus E2 glycoprotein alters interactions with cell surfaces and virulence in mice.


Liposome-antigen-nucleic acid complexes protect mice from lethal challenge with western and eastern equine encephalitis viruses.


Zoonotic encephalitides caused by arboviruses: transmission and epidemiology of alphaviruses and flaviviruses.


Eastern equine encephalitis in children, Massachusetts and New Hampshire, USA, 1970-2010.