Advances in BHV1 (IBR) research

Bovine Herpesvirus Type 1 (BHV1) is the aetiological agent of a number of diseases and not only of IBR, namely infectious pustular vulvovaginitis (IPV), infectious balanoposthitis (IBP), conjunctivitis, encephalomyelitis, mastitis, abortion, enteritis, and lesions in the interdigital space. The serological identical strains differ, however, in some aspects. Typical genital strains usually cause a mild illness, sometimes not even detected clinically, but serologically. They hamper eradication programmes and do not cause IBR when inoculated intranasally. The other--modern--strains are, however, always able to induce a severe disease in the genital tracts. But infection of field or vaccine virus leads to the development of humoral and cell-mediated immunity. The latter is, however, not transmitted to neonates via colostrum. BHV1 antibodies can be found in bovines in all continents, and in many wild species. Prevalences vary greatly depending on herd size and management. Because seronegative cattle play a role in international trade a number of European countries have eradicated BHV1, with very high costs involved. Marker and conventional vaccines can prevent disease but not infection followed by the state of latency. The genomes of several strains, including the marker strains can remain latent in the same animal and be reactivated after stress or injection of corticosteroids. For the detection of humoral antibodies the ELISA is widely used. It is useful for testing bulk milk samples for antibodies derived from field virus and conventional vaccines but not from gE-deleted marker vaccines. Importing countries should consider only vaccinated animals for import. They should require that the animals are seronegative prior to vaccination.