Detection of bovine herpesvirus type 1 in blood from naturally infected cattle by using a sensitive PCR that discriminates between wild-type virus and virus lacking glycoprotein E

In the present study, we report for the first time on the detection of bovi ne herpesvirus type 1 (BHV-1) in whole-blood samples derived from naturally infected cattle. Sensitive PCR assays specific for glycoprotein B (gB), gC , and gE of BHV-1 allow the detection of one BHV-1 DNA copy in 10(5) to 10( 7) peripheral blood leukocytes (PBLs). The incidence of BHV-1-positive PBLs in naturally infected cattle appears to be quite high (92.2% positive PBLs among all samples tested), although in most cases only between 10(-5) and 10(-7) positive leukocytes were present. The results demonstrate that the v iral DNA is detectable not only in the peripheral blood of acutely infected animals but, more importantly, also in the peripheral blood of subclinical ly infected cattle. The gE-specific PCR described in the report allows disc rimination between wild-type (WT) virus-infected and vaccinated animals, wh ich is of importance for control programs that use the recently introduced vaccination strategy with a gE-negative virus. The results further show tha t doubtful serological results can be verified or falsified and that indivi dual animals can be monitored for the presence or absence of WT BHV-1 or gE -negative virus in cattle herds. The PCR protocols allow the detection of B HV-1 prior to seroconversion or in BHV-1-seronegative cattle. Finally, the results indicate the simultaneous presence of WT and gE-negative vaccine vi rus in the PBLs of several cattle. Therefore, investigations of viremia in naturally and experimentally infected cattle and on the identification of i nfected cell types of bovine PBLs can be now performed.