Bovine gammaherpesvirus 6 (BoGHV6), previously known as bovine lymphotropic virus, is a member of the Macavirus genus, subfamily Gammaherpesvirinae. Other members of the genus Macavirus include viruses that produce malignant catarrhal fever (MCF) in mammalian hosts, collectively referred to as the MCF virus (MCFV) complex, and the porcine lymphotropic herpesvirus (PLHV). However, the current role of BoGHV6 in the development of diseases and/or disease syndromes remains uncertain and controversial. This paper investigated the participation of BoGHV6 in the development of pulmonary disease in a cow with interstitial pneumonia by histopathology and molecular testing. Tissue antigens of common viral agents of respiratory diseases and Mycoplasma bovis were not identified by immunohistochemistry. Additionally, molecular assays designed to amplify common bacterial and viral pathogens of pulmonary disease did not amplify the nucleic acids of these agents. However, a pan-PCR assay amplified the DNA of the herpesvirus polymerase gene, while the specific BoGHV6 nested-PCR assay amplified the partial fragment of the BoGHV6 polymerase gene derived from the pulmonary tissue with interstitial pneumonia. Phylogenetic analysis revealed that the BoGHV6 strain herein identified had 99.8% nucleotide (nt) sequence identity with reference strains of BoGHV6, but only 72.2–73.5% and 67.9–68.6% nt identity with reference strains of MCFV and PLHV, respectively. Consequently, these results suggest that BoGHV6 was associated with the pulmonary disease observed in this cow.

Bovine respiratory disease (BRD) is a significant global health issue in cattle farming, leading to substantial economic losses. This study analyzed the microbiological profiles of BRD outbreaks in nine dairy cattle herds in southern Brazil. We examined 36 biological samples, including 24 deep nasopharyngeal swabs (NS) and 12 lung tissue, from 29 suckling and 7 weaned heifer calves with acute BRD. PCR and RT-PCR techniques were used to partially amplify the genes of five viruses and four respiratory bacteria. A total of 8 different microorganisms, 4 viruses (bovine viral diarrhea virus, n = 5; bovine coronavirus, n = 3; bovine alphaherpesvirus 1, n = 3; and bovine parainfluenza virus 3, n = 2), and 4 bacteria (Pasteurella multocida, n = 16; Mycoplasma bovis, n = 8; Histophilus somni, n = 7; and Mannheimia haemolytica, n = 4) were identified in 29 (80.5%) samples. Seven samples (four lung tissue and three NS) were negative for all the microorganisms. Mixed infections were more common (62.1%) than single infections (37.9%). Bacterial nucleic acids were more commonly co-detected in NS than in lung tissue. Nucleic acids from a single pathogen were more frequently detected in lung tissues than in NS. M. bovis was the only bacterium detected in the lower respiratory tract. Understanding the microbiological profiles of the respiratory tracts of dairy calves with clinical signs of BRD is crucial for implementing effective biosecurity measures to prevent BRD in suckling and weaned dairy heifer calves.