n :  any of three encephalomyelitides that attack chiefly equines and humans in various parts of No. and So. America and are caused by three related strains of arbovirus  a  :  one that occurs esp. in the eastern U.S. - called also eastern equine encephalomyelitis   b  :  one that occurs esp. in the western U.S. - called also western equine encephalomyelitis   c  :  one that occurs esp. from northern So. America to Mexico - called also Venezuelan equine encephalitis , Venezuelan equine encephalomyelitis  .
 
 
 
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