Comparative pathogenicity of bovine herpesvirus 1 (BHV-1) subtypes 1 (BHV-1.1) and 2a (BHV-1.2a)

Abstract

The study aimed to examine the capacity of two bovine herpesvirus type 1 (BHV-1) isolates of different subtypes (EVI 123/96, BHV-1.1; SV265/98, BHV-1.2a) to induce respiratory disease in calves. These two isolates are representative of the BHV-1 subtypes prevalent in Brazil. Viral subtypes were confirmed by monoclonal antibody analysis and by restriction enzyme digestion of viral genomes. The viruses were inoculated intranasally into seven 3 months old calves (four with BHV-1.1, three with BHV-1.2a). Three other calves of identical age and condition were kept as uninfected controls. In both groups of infected calves, the clinical signs observed were consistent with typical infectious bovine rhinothracheitis (IBR), including pyrexia, apathy, anorexia, nasal and ocular mucopurulent discharges, erosions on the nasal mucosa, conjunctivitis, lachrymation, redness of nasal mucosa, dyspnoea, coughing, tracheal stridor and enlargement of retropharingeal, submandibular and cervical lymphnodes. No significant differences were observed between the clinical scores attributed to both groups. Virus shedding in nasal and ocular secretions were also similar, apart from a significant difference in nasal virus shedding on day 1 to 3 post-inoculation, which was higher for BHV-1.1 than for BHV-1.2a. Following corticosteroid induced reactivation of the latent infection, recrudescence of clinical signs was also observed, with no significant differences on both groups. It was concluded that both subtypes BHV-1.1 and BHV-1.2a were able to induce clinically undistinguishable respiratory disease in calves, either subsequent to a primary infection or following reactivation.

Phylogenetic analysis of glycoprotein B gene sequences of bovine herpesvirus 1 isolates from India reveals the predominance of subtype 1.1.

“…[30] who demonstrated that BoHV 1.1 is the common subtype in India. Subtypes 1.1 and 1.2 of BoHV-1 usually infect respiratory and genital tract of cattle, but many reports found that each subtype can be better adapted to either respiratory or genital tract [26,31]. Although a product length of 443 nucleotides (nts) was generated by PCR, only 400 nts corresponding to the position from 56,086 to 56,485 of Cooper strain (AJ004801) was aligned and used for nt sequence analysis due to non availability of that stretch of sequence from many other types/subtypes.…”

Bovine herpesvirus 1 infection and infectious bovine rhinotracheitis

“…Although most BoHV-1.1 strains have been isolated from respiratory tract diseases or abortion cases and BoHV-1.2 strains from genital organ lesions, the only reliable distinctive criterion is the viral DNA analysis by restriction endonuclease fingerprinting [45,128,137]. Indeed, calves infected experimentally by the nasal route with BoHV-1.2 strains showed respiratory clinical signs [44,190] and were able to transmit the respiratory infection to control calves [44,188]. Otherwise, reproductive tract lesions in heifers were observed after intrauterine inoculation with BoHV-1.1 [134].…”

Safety and immunogenicity of a glycoprotein E gene-deleted bovine herpesvirus 1 strain as a candidate vaccine strain

“…It should be emphasized that we performed a highly stringent challenge, using a high dose of a highly virulent virus (Spilki et al 2004). Unfortunately, no BoHV-1 vaccine has been shown to completely abolish virus shedding upon challenge, raising a concern about possible selection of escape mutants.…”