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United States Department of Agriculture

Agricultural Research Service

Research Project: CONTROL OF GAMMAHERPESVIRUS-ASSOCIATED MALIGNANT CATARRHAL FEVER IN RUMINANTS Title: Experimental nebulization of American bison (Bison bison) with low doses of ovine herpesvirus 2 from sheep nasal secretions

Authors
item Gailbreath, Katherine
item O'Toole, Donal - WY ST VET LAB
item Taus, Naomi
item Knowles, Donald
item Oaks, J -
item Li, Hong

Submitted to: Veterinary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 17, 2009
Publication Date: July 14, 2010
Repository URL: http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6TD6-4XSJVN9-6-3&_cdi=5190&_user=7810834&_pii=S0378113509005756&_orig=search&_coverDate=07%2F14%2F2010&_sk=998569997&view=c&wchp=dGLbVzz-zSkzV&md5=a8e20f6cb207a49c02cde55a67209718&ie=/sdarticle.pdf
Citation: Gailbreath, K.L., O'Toole, D., Taus, N.S., Knowles Jr, D.P., Oaks, J.L., Li, H. 2010. Experimental nebulization of American bison (Bison bison) with low doses of ovine herpesvirus 2 from sheep nasal secretions. Veterinary Microbiology. 143(2-4):389-393.

Interpretive Summary: Malignant catarrhal fever (MCF), caused by ovine herpesvirus 2 (OvHV-2), is an important cause of mortality in ranched American bison (Bison bison) in North America. It is now known that some bison are subclinically infected under natural conditions based on serology and PCR. A method of experimental infection has been developed involving intranasal nebulization with nasal secretions collected from sheep shedding high levels of virus. The purpose of this study was to determine the appropriate intranasal dose to give bison in order to induce subclinical infection and the dose required to consistently induce MCF. Sixteen bison were split into four dose groups and the results indicate that the dose required to induce subclinical infection and the lethal dose overlap, making production of subclinically infected animals by experimental methods impractical. In addition, it was determined that some of the animals were subclinically infected prior to nebulization, and all of these animals developed MCF, indicating the subclinical infection does not provide resistance to developing the disease. Another interesting finding was that there was a statistically significant correlation between dose and incubation period and between dose and the time to rise in OvHV-2 DNA level in peripheral blood. Conversely, no relationship was detected between dose and the time from rise in viral DNA to onset of clinical signs. These results suggest that dose may be more important than infection status in determining the outcome of OvHV-2 challenge and that detection of OvHV-2 DNA may be a useful tool for predicting disease onset regardless of inoculation dose.

Technical Abstract: Malignant catarrhal fever (MCF), caused by ovine herpesvirus 2 (OvHV-2), is an important cause of mortality in ranched American bison (Bison bison) in North America. Detection of antibody against MCF-group viruses and OvHV-2 DNA in peripheral blood of healthy bison indicates that some are subclinically infected. Previous studies have shown that bison can be infected by intranasal nebulization with nasal secretions from sheep (the reservoir) that are shedding virus and have provided preliminary information on infectious and lethal doses. The purpose of this study was too refine the minimum infectious and lethal doses of OvHV-2 and to determine if bison that were subclinically infected prior to nebulization are resistant to developing MCF after challenge with a dose that is lethal in uninfected bison. Sixteen yearling bison were split into four dose groups and the results indicate that the minimum infectious dose and minimum lethal dose overlap, suggesting that experimental production of subclinically infected bison is unlikely to be a practical option. In addition, subclinical infection did not confer resistance to MCF, even after low dose challenge. There was a statistically significant relationship between inoculation dose and incubation period, while no relationship was detected between dose and time from rise in OvHV-2 DNA level in the peripheral blood to onset of clinical signs. These results suggest that dose may be more important than infection status in determining the outcome of OvHV-2 challenge and that detection of OvHV-2 DNA may be a useful tool for predicting disease onset regardless of inoculation dose.

Last Modified: 10/22/2014