The aim of the study is determination of the BHV 1 incidence among the bovine population in Bulgaria by using various ELISA tests for antibody detection and diff erent methods for proving viral antigen. Commercial diagnostic ELISA kits were used for screening as well as for confi rmation of the antibodies. Serological examination encompassed 2973 serum samples from bovine population in Bulgaria (cattle, calves and bulls) originating from 21 country regions. Total 408 cattle and 150 bulls’ samples originating from artifi cial insemination centers (AIC), commune and private farms from 21 country regions were subjected to virology testing. Identifi cation of isolated viruses was performed using conventional and nested PCRs for BHV 1 gB gene detection. Th e percentage of positively reacting cattle sera were signifi cantly (p < 0.001) higher (38.3%) then that of bulls (29.3%) after ELISA testing of 2240 cattle serum samples and 733 bulls’ sera. Seven strains with BHV 1 characteristics were isolated from Dobrich, Lovech – 2 strains, Plovdiv, Targovishte, Pazardjik and Svishtov regions after cultivation 408 samples from cattle and calves (buff y coats, nasal, eyes, vaginal swabs, tissues and organs) on cell cultures. Th ree BHV 1 strains were isolated from Sliven, Shumen and Blagoevgrad regions aft er examining 150 bulls’ samples (nasal, eyes, preputial, semen samples and buff y coats). Confi rmation of virus isolation was accomplished using PCR gB gene based primers (amplified 478 bp) Th e amplicons from 3 bulls isolated strains with the same size and location as the referent Oxford strain were observed. After performance of nested PCR for gB gen, products with size of 385 bp were obtained in all samples as well as in the referent Oxford strain.
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