Equine herds as sentinels for Venezuelan Equine encephalitis virus activity, Nicaragua 1977.

The Central American equine epizootic and epidemic of Venezuelan equine encephalitis (VEE) that began in June 1969 near the Guatemala-El Salvador border has been welldocumented (1-S). That outbreak spread southeast, reaching Guanacaste, Costa Rica, by 1970, and north, reaching southern Texas in 1971. The last known cases of equine infection by the exotic equine-virulent subtype I-AB strain of VEE virus in Central America occurred in Nicaragua’s Chinandega Department during April-July 1972 (7). Whether that activity was caused by virus remaining from the 1969 outbreak in Nicaragua or whether it resulted from reintroduced virus is unknown (7). Extensive searches for persistent activity by epizootic strains of VEE virus in Guatemala, El Salvador, and Nicaragua during 1970-1975employing sentinel horses and sentinel hamsters, serologic surveys of humans and wild rodents, and attempts to isolate the virus