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United States Department of Agriculture

Agricultural Research Service

Title: Demonstration of Sheep-Associated Malignant Catarrhal Fever Virions in Sheep Nasal Secretions

Authors
item Kim, Okjin
item Li, Hong
item Crawford, Timothy - WASHINGTON STATE UNIV

Submitted to: Virus Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 2, 2003
Publication Date: October 1, 2003
Citation: Kim, O., Li, H., Crawford, T.B. 2003. Demonstration of sheep-associated malignant catarrhal fever virions in sheep nasal secretions. Virus Research. 98:117-122.

Interpretive Summary: Ovine herpesvirus-2(OvHV-2)is the causative agent of sheep-associated malignant catarrhal fever, which has never been isolated in cell culture. Previous studies from this laboratory found high levels of the viral DNA in sheep nasal secretions, suggesting a likely avenue of transmission. In order to confirm that the high levels of viral DNA in nasal secretions represent active viral shedding, we designed an experiment to demonstrate the presence of intact OvHV-2 viral particles in nasal secretions. The sheep experiencing an episode of intense viral DNA shedding were identified by quantitative real-time PCR. The presence of intact cell-free enveloped OvHV-2 particles in nasal secretions was examined using a nuclease-resistance assay, based on the ability of the viral outer envelope to shield viral capsid and DNA from enzymatic digestion. The results revealed that all nasal secretion samples from 5 selected individuals experiencing intensive shedding events contained cell-free OvHV-2 viral particles. Viral particles could not be found in secretion samples from 11 OvHV-2 infected sheep that were not experiencing a shedding event. This is the first unequivocal demonstration of cell-free intact OvHV-2 virus. These results suggest that OvHV-2 replication occurs in tissues of sheep upper respiratory tract.

Technical Abstract: Ovine herpesvirus-2(OvHV-2)is the causative agent for sheep-associated malignant catarrhal fever, which has never been propagated in vitro. Previous studies from this laboratory demonstrated significantly high levels of OvHV-2 DNA in sheep nasal secretions, suggesting a likely avenue of transmission. In the present study, real-time PCR was used to identify sheep experiencing an episode of intense OvHV-2 DNA shedding in their nasal secretions. A nuclease-resistance assay was used to examine the secretions for the presence of intact cell-free enveloped OvHV-2 virions. The results revealed that all nasal secretion samples from 5 selected individuals experiencing intensive shedding events contained cell-free OvHV-2 virions. Virions could not be identified in secretion samples from 11 OvHV-2 infected sheep that were not experiencing a shedding event. This is the first unequivocal demonstration of cell-free OvHV-2 virions. These results suggest that OvHV-2 lytic infection occurs in the epithelium of certain tissues in the upper respiratory tract of the natural host.

Last Modified: 7/28/2014