Epidemiological survey of bovine gammaherpesvirus 4 (BoHV-4) infection in cattle and buffalo from Pakistan

Abstract

This study was conducted to evaluate the prevalence of bovine gammaherpesvirus 4 (BoHV-4) among healthy cattle and buffaloes as well as those associated with different diseases (respiratory tract infection, mastitis and reproductive tract infection) in District Chakwal, Pakistan. Blood, swab and milk samples of cattle and buffaloes were randomly collected from different areas of Chakwal. DNA was isolated from the samples and subjected to nested PCR using thymidine kinase gene primers. Out of 300 samples (200 blood, 50 swab and 50 milk samples) from both species (cattle and buffalo), an overall prevalence of BoHV-4 of 3.33% was obtained. Samples from cattle showed a higher species-specific prevalence (4.16%) than samples from buffalo (2.78%). One sample out of 50 swab samples and 1 out of 50 milk samples were also positive for BoHV-4. DNA sequencing of a positive PCR product from cattle confirmed that the sequence was from the thymidine kinase gene of BoHV-4. Phylogenetic analysis also revealed close similarities with other BOHV-4 thymidine kinase sequences. To detect BoHV-4 antibodies, an indirect ELISA was also performed. Two hundred blood samples were also collected from the same animals in nonanticoagulant-containing tubes for the isolation of serum and were subjected to indirect ELISA. Sixteen samples (8%) were positive for BoHV-4 antibodies. This study will be useful in further diagnoses of BoHV-4 in Pakistan and in devising measures to control the spread of BoHV-4.

Keywords: Bovine gammaherpesvirus 4; Mastitis; Nested PCR; Pakistan.