Serum neutralisation (SN) and immunoblotting were used in attempts to
distinguish between natural infections with the closely related viruse
s equine herpesvirus 1 (EHV-1) and equine herpesvirus 4 (EHV-4), Horse
sera (n = 323) collected in 1990 from studs with no experience of EHV
-1 abortions as well as 197 sera collected in 1992 from studs with a h
istory of EHV-1 abortions were tested by SN. The two groups differed i
n the proportion with measurable EHV-1 antibody, the 1992 group being
significantly higher. Both groups had high proportions with EHV-4 anti
body and no serum had antibody to EHV-1 alone, Pools of positive sera
were prepared as probes in immunoblots. High molecular weight (> 200 k
Da) polypeptide bands specific for EHV-4 were detected. No bands speci
fic for EHV-1 only were found. The specific EHV-4 polypeptides shared
some properties with gp2 of EHV-1.