Detection of bovine herpesvirus 1 from an outbreak of infectious bovine rhinotracheitis

Clinical symptoms from the respiratory tract were observed in cattle after the introduction of pregnant heifers into the dairy herd. Sera and nasal swabs from all animals and tissue samples from two dead animals were tested for BHV1. Specific antibodies against BHV1 were found in serum samples of 24 animals. Only one sample reacted doubtfully in gB ELISA. The virus was isolated only from nasal swabs and lungs collected from 2 weeks old calf. The remaining samples were negative in virus isolation test. PCR with external primers detected the presence of BHV1 in 11 nasal swabs and in lung and liver samples of 2 weeks old calf. In nested PCR almost all tested samples were positive. Restriction enzyme analysis confirmed the specificity of amplification. Results of laboratory diagnosis revealed that introduction of newly purchased animals into the herd initiated the outbreak of disease caused by BHV1.