Submitted to: Journal of General Virology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/6/2004
Publication Date: 4/21/2005
Citation: Taus, N.S., Traul, D., Oaks, J.L., Crawford, T.B., Lewis, G.S., Li, H. 2005. Experimental infection of sheep with ovine herpesvirus 2 via aerosolization of nasal secretions. Journal of General Virology. 86:575-579. Interpretive Summary: Ovine herpesvirus-2 (OvHV-2) is a gammaherpesvirus that exists in most sheep world-wide as a subclinical, persistent infection. When OvHV-2 infects ruminants, such as cattle, bison, and deer, a fatal disease syndrome known as malignant catarrhal fever (MCF) can result. Because OvHV-2 has not yet been able to be grown in cell culture, a standardized source of virus for animal infection studies is not available. In this study, we have showed that nasal secretions collected from OvHV-2 infected sheep experiencing virus shedding episodes can be used to infect OvHV-2 negative sheep. We developed a pool of nasal secretions containing infectious OvHV-2 that will be used in studies of viral pathogenesis and vaccine development.
Technical Abstract: Ovine herpesvirus-2 (OvHV-2) is the causative agent of sheep-associated malignant catarrhal fever in clinically susceptible ruminants, including cattle, bison, and deer. Studies of OvHV-2 have been hampered by the lack of an in vitro propagation system. We examined the use of nasal secretions collected from OvHV-2 infected sheep experiencing intense virus shedding episodes as a source of infectious virus for experimental animal infections. OvHV-2 uninfected sheep were nebulized with nasal secretions containing approximately 108, 106, 104, 103, 102, and 101 copies of OvHV-2 DNA. Control sheep were nebulized with nasal secretions collected from OvHV-2 uninfected sheep. Blood and nasal secretion samples were examined with semi-nested and real-time PCR for viral DNA. Plasma was examined with competitive-inhibition ELISA for virus specific antibody. Beginning 7-21 days post exposure, OvHV-2 DNA was detected in peripheral blood leukocytes (PBL) from sheep nebulized with inoculum containing 108 to 103 genome copies of OvHV-2. Virus specific antibody was detected beginning at 9-32 days post exposure. The time to detectable viral DNA and virus specific antibody tended to vary with the dose of inoculum administered. Control sheep and sheep nebulized with inoculum containing 102 and 101 genome copies of OvHV-2 remained negative for virus specific antibody and viral DNA for 120 days. We have defined the use of nasal secretions as a source of infectious OvHV-2 and determined the minimum infectious dose of a pool of nasal secretions that can be used in further studies of viral pathogenesis and vaccine development.