In the epidemiology of bovine viral diarrhoea (BVD),
immunotolerant – persistently infected
animals (IPI) appear to be major sources of contamination. These animals
produce large
quantities of replicating virus and have therefore been proposed as being
responsible for
generating antigenic variability. However, limited studies have failed
to detect antigenic or
genetic changes in viruses isolated at different times from IPI. An hypothesis
is that the
immunotolerance of IPI against their homologous strain is accompanied by
immune
elimination of antigenic variants. The presence of an IPI in a herd could
therefore limit
antigenic variation, eventually leading to the existence of herd specific
strains. To verify this
hypothesis we characterized, against a panel of monoclonal antibodies,
37 BVD virus strains
isolated from IPI of 12 herds in Eastern Belgium. Intra-herd antigenic
variation was compared
to inter-herd variation. Antigenic variation within herds was found to
be surprisingly high but,
nevertheless, significantly lower than variation between herds.