Virulence and genotype of a bovine herpesvirus 1 isolate from semen of a subclinically infected bull.

A bovine herpesvirus 1 (BHV-1) isolate from the semen of a subclinically infected bull was administered to cattle by various routes to assess its virulence. Cattle that were artificially inseminated or inoculated intrapreputially did not develop clinical signs, but did transmit the virus to contact cattle. However, the isolate induced severe signs of rhinotracheitis and vulvovaginitis in cattle that were inoculated by the intravaginal, intranasal or intravenous routes, but did not infect the fetus. The isolate was therefore not of low virulence. Analysis with DNA restriction enzymes could not assign the isolate to either the BHV-1.1 or BHV-1.2 genotype.