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January 7, 1939

Current Comment

JAMA. 1939;112(1):52. doi:10.1001/jama.1939.02800010054016

VENEZUELAN EQUINE ENCEPHALOMYELITIS  Coincident with the recent severe epidemics of equine encephalomyelitis in Canada and the United States, a similar disease was recognized in Venezuela. Portions of the brains of horses dying of this disease were sent to Beck and Wyckoff 1 of the Lederle Laboratories for comparison with the northern types. When inoculated into guinea pigs and mice the Venezuelan virus produced symptoms similar to those of eastern encephalomyelitis. The virus, however, was from ten to a hundred times more virulent (or in greater concentration) than the usual eastern strain. Vaccines made from the Venezuelan strain and treated with formaldehyde would confer a solid immunity against the Venezuelan type. Cross protection tests, however, showed that solid immunity against the western virus was not accompanied by a demonstrable increase in resistance against the Venezuelan strain. Eastern immune guinea pigs also could be infected with the South American strain. A solid