equine encephalitis /ē″kwīn, ek″win/ [L, equus, horse; Gk, enkephalon, brain, itis, inflammation] , an arbovirus infection with a member of the Togaviridae family, Alphavirus, characterized by inflammation of the nerve tissues of the brain and spinal cord. Other characteristics include high fever, headache, nausea, vomiting, myalgia, and neurological symptoms, such as visual disturbances, tremor, lethargy, and disorientation. The virus is transmitted by the bite of an infected mosquito. Horses are the primary host of the viruses that cause the infection; humans are secondary hosts. Because horses are deadend hosts, they are not a significant risk factor for human infection. Eastern equine encephalitis (EEE) is a severe form of the infection, with a mortality rate of 33%. The main EEE transmission cycle is between mosquitoes and birds, specifically the mosquito Culiseta melanura. EEE occurs primarily along the eastern seaboard of the United States and lasts longer and causes more deaths and residual morbidity than western equine encephalitis (WEE), which occurs throughout the United States and produces a mild, brief illness, as does Venezuelan equine encephalitis (VEE), which is common in Central and South America, Florida, and Texas. See also encephalitis, encephalomyelitis, eastern equine encephalitis, western equine encephalitis, Venezuelan equine encephalitis.
