TRANSMISSION OF OVINE HERPESVIRUS-2 IN LAMBS

The pattern of acquisition of ovine herpesvirus 2 (OHV-2) infection in lambs was examined by a competitive-inhibition enzyme-linked immunoso rbent assay and PCR Newborn lambs (n = 118) did not exhibit antibody a t birth, Viral DNA in peripheral blood leukocytes was detected in only 3% (n = 77) of newborn lambs before suckling, After nursing, viral DN A was sporadically present in about 10 to 20% of lambs until about 3 m onths of age. Thereafter, strong DNA signals began to appear in increa sing numbers of lambs, reaching 100% by 5.5 months of age, Viral DNA i n nasal secretions began to be detectable in about 30% of lambs at 5.5 months of age, achieved significant levels in 88% of lambs by 7.5 mon ths of age, and then declined. The kinetics of the humoral immune resp onse in lambs paralleled those of viral DNA in nasal secretions but di d not parallel its presence in blood leukocytes. In the experiment to define the time of infection of OHV-2 in lambs, all five lambs separat ed from the flock at 2.5 months of age remained uninfected until the t ermination of the experiment at 1 year of age, In contrast, lambs wean ed at 2.5 months of age and returned to the flock had become infected at 3.5 months of age, Weaning and separation from the flock at 3.5 mon ths of age did not prevent infection, The study showed that OHV-2 infe ction does not commonly occur in perinatal lambs and that OHV-2-free s heep can be established by separation of lambs at the proper time, whi ch has important implications for potential control measures.