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United States Department of Agriculture

Agricultural Research Service

Title: Successful Experimental Induction of Acute Malignant Catarrhal Fever in Bison Using Aerosols of Ovine Nasal Mucus Containing Ovine Herpesvirus 2

Authors
item O'Toole, D - UNIVERSITY OF WY
item Taus, Naomi
item Davis, W - WSU
item Crawford, T - WSU
item Li, Hong

Submitted to: American Association of Veterinary Laboratory Diagnosticians
Publication Type: Abstract Only
Publication Acceptance Date: July 5, 2004
Publication Date: October 22, 2004
Citation: O'Toole, D., Taus, N.S., Davis, W.C., Crawford, T.B., Li, H. 2004. Successful experimental induction of acute malignant catarrhal fever in bison using aerosols of ovine nasal mucus containing ovine herpesvirus 2. American Association of Veterinary Laboratory Diagnosticians. 55.

Interpretive Summary: Following the recognition that aerosolized nasal mucus from sheep undergoing intense viral shedding could transmit infection to uninfected sheep (Kim, et al, Virus Res. 2003, 98:117), we conducted two studies to establish whether aerosol exposure could induce MCF in bison. In study 1, four bison were aerosolized with 2 ml nasal secretions containing 2.7 to 4.7 x 10(7) OvHV-2 DNA copies from sheep experiencing intensive shedding events. By 16 to 20 days post-aerosolization (DPA), the four bison were serologically positive. By 16 to 24 DPA, OvHV-2 DNA was detectable by nested PCR in peripheral blood leukocytes of all four bison. The four died 29, 29, 41 and 49 DPA. All four had gross and histological lesions typical of MCF, comprising colitis, cystitis, abomastitis and vasculitis. In study 2, eight yearling bison were used. Four served as inoculated principals, four were used as controls. The principals were nebulized with a mixture of nasal secretions (~2.35 x 10(7) copies from the same inoculum of sheep as in study 1). The control bison were inoculated with nasal mucus collected from an OvHV-2 negative sheep. In the principle group, all animals became PCR-positive between 38 to 75 DPA. Only one animal developed clinical signs of MCF and died at 66 DPA. All control bison remained PCR-negative and none developed clinical signs by the end of the study. In conclusion: 1) aerosolization using nasal mucus derived from sheep experiencing intensive shedding events of OvHV-2 is a viable way to induce clinical MCF in bison; 2) developing pooled, standardized inocula from sheep shedding OvHV-2 is an important goal in order to develop a challenge model of MCF; 3) significantly different outcomes between study 1 and study 2 might be attributable to insufficient nebulization procedures due to a frozen nebulizer tube during the severe weather conditions (-20 C); and 4) dose of inoculum may be a factor determining whether and when bison develop MCF, or become latently infected.

Technical Abstract: Following the recognition that aerosolized nasal mucus from sheep undergoing intense viral shedding could transmit infection to uninfected sheep (Kim, et al, Virus Res. 2003, 98:117), we conducted two studies to establish whether aerosol exposure could induce MCF in bison. In study 1, four bison were aerosolized with 2 ml nasal secretions containing 2.7 to 4.7 x 10(7) OvHV-2 DNA copies from sheep experiencing intensive shedding events. By 16 to 20 days post-aerosolization (DPA), the four bison were serologically positive. By 16 to 24 DPA, OvHV-2 DNA was detectable by nested PCR in peripheral blood leukocytes of all four bison. The four died 29, 29, 41 and 49 DPA. All four had gross and histological lesions typical of MCF, comprising colitis, cystitis, abomastitis and vasculitis. In study 2, eight yearling bison were used. Four served as inoculated principals, four were used as controls. The principals were nebulized with a mixture of nasal secretions (~2.35 x 10(7) copies from the same inoculum of sheep as in study 1). The control bison were inoculated with nasal mucus collected from an OvHV-2 negative sheep. In the principle group, all animals became PCR-positive between 38 to 75 DPA. Only one animal developed clinical signs of MCF and died at 66 DPA. All control bison remained PCR-negative and none developed clinical signs by the end of the study. In conclusion: 1) aerosolization using nasal mucus derived from sheep experiencing intensive shedding events of OvHV-2 is a viable way to induce clinical MCF in bison; 2) developing pooled, standardized inocula from sheep shedding OvHV-2 is an important goal in order to develop a challenge model of MCF; 3) significantly different outcomes between study 1 and study 2 might be attributable to insufficient nebulization procedures due to a frozen nebulizer tube during the severe weather conditions (-20 C); and 4) dose of inoculum may be a factor determining whether and when bison develop MCF, or become latently infected.

Last Modified: 9/22/2014
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