USE OF THE SERUM NEUTRALIZATION TEST FOR EQUINE VIRAL ARTERITIS WITH DIFFERENT VIRUS-STRAINS

Serum cross neutralisation tests were conducted with a recent American isolate (84KY-A1) and a European isolate, (Wroclaw-2) and compared wi th the prototype and modified viruses of the Bucyrus strain of equine arteritis virus by using virus specific immune horse sera. The modifie d Bucyrus strain was neutralised and showed high neutralisation titres with all the immune sera. The prototype Bucyrus strain was also subst antially neutralised, followed by the 84KY-A1 strain. As a result of t he tests with the modified Bucyrus strain as the antigen, 20 seroposit ive horses mere discovered among home-bred horses which had no previou s record of clinical equine viral arteritis. Heat inactivation of the sera at 62 degrees C for 30 minutes caused the disappearance of all bu t the most positive reactions. When the prototype Bucyrus strain was u sed instead of the modified virus, no positive reactions mere detectab le. A serological survey, using the Bucyrus strain in a microtitre neu tralisation test, was conducted with 1656 horse sera collected between 1988 and 1990 in Japan. The test disclosed only eight foreign-bred ho rses positive to the virus; they had been imported as competition hors es. No circumstantial evidence of an effect of such horses as a source of infection for horse populations free of the virus was obtained.