Emerging Evidence of Border Disease Virus in Indian Buffaloes Co-infected with Sheep Associated MCF: Clinical Signs, Molecular Characterization and Phylogenetic Insights

Abstract

Aim: To investigate the etiological agents involved in mortality of buffaloes in Andhra Pradesh, India. Study Design: This was an observational diagnostic study involving clinical evaluation, molecular diagnostics, sequencing and phylogenetic analysis to confirm the etiological agent. Place and Duration of Study: The study was conducted in Srungavarapukota, Vizianagaram, Andhra Pradesh, India during November 2023. Methodology: Three adult buffaloes aged between 5 to 6 years showing clinical signs such as pyrexia, congested eyes with ocular discharge, respiratory distress, mucopurulent nasal discharge and diarrhoea were suspected for viral infections such as Infectious Bovine Rhinotracheitis (IBR), Malignant Catarrhal Fever (MCF), or Bovine Viral Diarrhoea (BVD). To identify the etiological agents involved blood and Nasal swabs were collected aseptically and molecular diagnostic assays such as PCR were employed to detect IBR by amplifying the glycoprotein B (gB) gene, MCF by Ovine herpesvirus 2 (OvHV-2) tegument gene and BVD by Pestivirus-specific 5′ UTR. Additionally, samples were tested using the BVD P80 antigen capture ELISA. PCR products from one animal that tested positive for both OvHV-2 and Pestivirus were sequenced and Phylogenetic trees were constructed using the resulted sequences. Results: All three buffaloes tested negative for IBR by PCR and for BVD by ELISA. However, PCR testing revealed that all samples were positive for both OvHV-2 and Pestivirus. In BLAST analysis the PCR products were confirmed as OvHV-2 and Border Disease Virus (BDV). Phylogenetic analysis revealed that the OvHV-2 sequence clustered with previously reported isolates from Andhra Pradesh, while the Pestivirus sequence showed high genetic identity with a BDV-3 isolate reported in sheep from NIHSAD, Bhopal, India and exhibited significant genetic divergence from Classical Swine Fever Virus (CSFV), Bovine Viral Diarrhoea Virus (BVDV), and other BDV sub genotypes. Conclusion: The findings of this study conclusively demonstrate that the affected buffaloes were co-infected with sheep associated Malignant Catarrhal Fever Virus (OvHV-2) and Border Disease Virus. The synergistic action of these viruses exacerbated the pathogenicity resulting in mortality of the three affected animals. Notably, sheep acted as primary reservoir for both diseases, underscoring the risk of interspecies transmission within mixed farming systems.