title: Venezuelan equine encephalitis virus: comparison of infectivity and virulence of strains V-38 and P676 in donkeys.
abstract: Two strains of Venezuelan equine encephalitis (VEE) virus were examined for the ability to replicate in, as well as to produce death among donkeys. One, a low passage strain known as strain P676 was originally isolated from mosquitos in Venezuela. The other, strain V-38 was isolated from a horse brain in 1938 and had undergone an unknown number of laboratory passages; it is used extensively for the preparation of inactivated VEE vaccine. Both strains were found to be approximately equal in their ability to infect donkeys. However, a quantity as small as 50% hamster intraperitoneal infectious units of strain V-38 resulted in fatal infection. On the other hand, as much as 631 million infectious units of strain P676 were nonfatal in one of two donkeys. It appears that strain V-38 is approximately 100 million times more virulent than strain P676 in equine species. One donkey which received strain P676 demonstrated a biphasic pattern of clinical illness and viremia, and there is suggestive evidence that another animal experienced a second and fatal clinical response 3 weeks after virus inoculation.
mesh_terms: D000818:Animals; D004666:Encephalitis Virus, Venezuelan Equine / Q000254:growth & development / Q000276:immunology / Q000472:pathogenicity*; D004683:Encephalomyelitis, Equine / Q000401:mortality*; D004685:Encephalomyelitis, Venezuelan Equine / Q000401:mortality*; D010527:Perissodactyla; D014774:Virulence; D014779:Virus Replication