Isolation, identification and extent of positivity of Bubaline alphaherpesvirus 1 (BuAHV1) in India.

Abstract

Infectious bovine rhinotracheitis (IBR), caused by bovine alphaherpesvirus 1 (BoAHV1), is a significant economic challenge to the dairy industry worldwide. This study investigated the prevalence and characteristics of bubaline alphaherpesvirus 1 (BuAHV1) in water buffaloes in India, a species crucial to the country's dairy industry. Extended frozen semen (EFS) from cattle and buffaloes was screened for ruminant herpesvirus using MDBK cell lines. Cytopathic effects (CPEs) indicative of herpesvirus infection were confirmed by real-time PCR targeting the gB gene. Phylogenetic analysis of glycoprotein genes [UL27 (gB), UL44 (gC), US6 (gD), and US8 (gE)] identified three BuAHV1 isolates, which clustered with Brazilian strains. Serum samples collected from the infected bulls were positive in gB ELISA and negative in gE ELISA test. Cross-neutralization assays revealed that, the serum neutralized both the BoAHV1 and BuAHV1 viruses, with higher titres recorded for the BuAHV1 virus. Epidemiological analysis of IBR-positive serum samples (n = 677) by a differential ELISA indicated widespread BuAHV1 infection in buffaloes (29.6%) and cattle (6.6%). The results of the majority of the samples (54.1%) were inconclusive suggesting likely co-infection. The presence of both BoAHV1 and BuAHV1 was recorded in 24 out of the 39 farms studied. These findings underscore the need for further research to understand the epidemiology, pathogenic potential and impact of BuAHV1 on productivity in ruminants, facilitating the development of targeted control measures.