First detection and impact of bovine herpesvirus type 4 on dairy cattle reproduction in Thailand.

Abstract

Background and aim: Postpartum reproductive tract infections pose significant challenges to dairy farms, leading to economic losses due to reduced fertility associated with uterine inflammation. In veterinary practice, numerous research groups have explored the underlying causes of subfertility in cows, including surveying endemic viral infections related to endometritis in local areas. This study investigated bovine herpesvirus 4 (BoHV-4) infection in Thai dairy herds and assessed its impact on endometritis and subsequent reproductive outcomes.

Materials and methods: The present study analyzed BoHV-4 DNA in various samples, including milk, blood, and endometrial tissue, from 44 Holstein-Friesian cows 21-47 days postpartum across five dairy herds in Central Thailand. BoHV-4 glycoprotein B and thymidine kinase DNA sequences were detected using the polymerase chain reaction (PCR) and nested PCR, with sequence comparisons made to GenBank data for phylogenetic analysis. The endometritis status was diagnosed through vaginal mucus examination and endometrial cytology, with reproductive performance monitored up to the subsequent calving.

Results: BoHV-4 DNA was identified in blood and endometrial tissues (15.91%) but not in milk samples. Phylogenetic analysis revealed that the local BoHV-4 strains are similar to those identified in Brazil and Japan. Notably, the presence of BoHV-4 was correlated with reduced postpartum reproductive performance, particularly extending the interval from calving to the first service.

Conclusion: Our findings underscore the importance of integrating BoHV-4 genomic surveys and uterine health assessments to refine reproductive management strategies within the dairy industry.