Experimental infection of calves with bovine gammaherpesvirus 4

Authors: BAUERMANN, FERNANDO - South Dakota State University; Falkenberg, Shollie; Dassanayake, Rohana; SILVERIA, SIMONE - Federal University Of Rio Grande Do Sul; MARTINS, M - South Dakota State University; Neill, John; Ridpath, Julia; BUYSSE, A - South Dakota State University; MOHR, A - South Dakota State University; DIEL, DIEGO - South Dakota State University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/17/2018
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Bovine gammaherpesvirus 4 (BoHV-4) has been one of the most frequently isolated viruses from bovine samples collected from cattle at the South Dakota State University, Animal Disease Research and Diagnostic Laboratory. However, the potential role of BoHV-4 in the bovine respiratory disease complex (BRDC) remains largely unknown. In the present study, it was investigated if a contemporary BoHV-4 isolate could induce clinical disease and whether the virus could be transmitted to naïve contact animals. For this, 10 colostrum-deprived calves were inoculated intranasally with BoHV-4 isolate SD16-38 (5 x 106.5 TCID50; 2.5 ml/nostril), and on day 3 post-inoculation (pi) four non-inoculated contact animals were comingled with four of the inoculated calves. Four control calves were mock inoculated intranasally with cell culture medium and housed separately from the inoculated animals. Serial necropsies were conducted to evaluate the progression of infection on days 5, 10 and 35 pi. Blood samples were collected prior to inoculation on day 0 and on days 3, 5, 7, 10, and 35 pi and used for flow cytometric analysis, complete blood counts, virus neutralization assays, and assessment of viremia by nested PCR. At necropsy, tissues were collected for viral detection by nested PCR and RNAscope. No clinical signs of respiratory disease were observed in any of the BoHV-4 inoculated calves nor in the contact animals. A slight increase in temperature was observed in the BoHV-4-inoculated calves on days 7-9 pi. Additionally, lymphopenia was observed in BoHV-4 inoculated animals on day 5 pi and this decrease appeared to be more pronounced in the B-lymphocytes (sIgM+). Virus shedding was detected in nasal secretions from all BoHV-4-inoculated calves, however no virus was detected in the contact animals. The virus DNA was also detected in tissues of all but one BoHV-4-inoculated calf necropsied at 5dpi, no virus was detected in tissues from direct contacts. RNAscope analysis in the tissues confirmed the presence of BoHV-4 in lymph nodes and nerve fibers surrounding the trigeminal ganglia from calves necropsied on day 35 pi. Interestingly, neutralizing antibodies were only detected late after infection in the two animals that were kept until day 35 pi. Results here show that BoHV-4 caused subclinical infection in calves and further suggest that the virus is not readily transmitted by direct contact. Detection of the virus DNA in lymph nodes and trigeminal ganglia on day 35 pi suggest that the virus may establish latent infection in lymphoid- and neuronal cells. This study presents important information on the initial aspects of BoHV-4 respiratory infection in cattle.