The immunogenicity and efficacy of acommercially available Infectious Bovine Rhinotracheitis (IBR) virus vaccine against a Pakistani field IBR strain.

Infectious bovine rhinotracheitis (IBR) is a highly communicable disease of cattle and wild ruminants that is caused by Bovine alphaherpesvirus 1 (BoHV­1). For IBR control, several developed countries have adopted the immunization and eradication programs focusing on IBR­positive animals. In Pakistan, livestock producers are importing commercially available vaccine of BoHV­1, but no studies on the efficacy of these commercial vaccines against local isolates are available. Therefore, the present study was aimed to evaluate the efficacy of a commercially available vaccine of BoHV­1 against local field isolates of virus. The rabbit model was used and the vaccine was evaluated for immunogenicity and protection after challenge with a highly virulent strain of a field virus. The immune response was measured by virus neutralization titers (VNT). This vaccine induced a humoral response in rabbits but that was not sufficient to completely protect the vaccinated animals against the wild­type BoHV­1 strain challenge. While a low virus titer compared to control rabbits was observed in the vaccinated rabbits (p<0.05), there was no sterilizing immunity or freedom from infection. However, complete freedom from disease, for example, the absence of pyrexia was noticed in the vaccinated group. In conclusion, the present study demonstrated that imported vaccine stock provoked only a partial protection against indigenous isolated of BoHV­1. However, tests performed on rabbits are preliminary, as only those performed on the source species can determine more reliable results.