BHV1 infections: relevance and spread in Europe.

Infections caused by BHV1 are very common in Europe, but the disease pattern is quite different: the diseases of the genital tract are most common, those of the respiratory tract vary in intensity and prevalence. Digestive disorders connected with BHV1 are in general only observed in calves and mainly in Belgium. Virus strains causing abortion or encephalitis are only present in a few countries. The same is true for BHV1 induced mastitis. Dermatitis and lesions in the interdigital space seem to be a rare event. BHV1 infections are frequently complicated by bacterial secondary infections, but there is evidence that BHV1 infections can occur simultaneously with bovine virus diarrhoea (BVD) and/or parainfluenza-3 (PI 3) virus. The biggest problem associated with BHV1 infection is the ability of the agent to become latent following a primary infection. The genome of the virus probably remains during the life of the animal in the ganglia of the region where the primary infection occurred. No vaccination can overcome this latent stage. By prophylactic vaccination it is possible to prevent an outbreak of clinical disease but it is impossible to prevent infection followed by the establishment of latency. Eradication programmes in Austria, Denmark and Switzerland have removed most of the seropositive cattle from the bovine populations. Currently a sanitary programme is also being conducted in Germany.