Location: Animal Disease Research Unit
Project Number: 2090-32000-045-003-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jan 31, 2026
End Date: Jan 30, 2029
Objective:
The objective of this collaborative research is to evaluate the safety and efficacy of sheep-associated malignant catarrhal fever (SA-MCF) vaccine candidates through vaccine trials in bison.
Approach:
Sheep-associated Malignant Catarrhal Fever (MCF) is a usually fatal disease of ungulates caused by ovine herpesvirus 2 (OvHV-2), which is transmitted by sheep. ARS has developed a chimeric virus expressing OvHV-2 glycoproteins B, which was tested as a vaccine candidate in a laboratory model (rabbits) and in natural hosts (cattle and bison). These trials demonstrated that the viral-vectored vaccine is safe and immunogenic for all three species. The vaccine candidate provided protection against disease in 71% of rabbits challenged with a fatal dose of OvHV-2, confirming the potential of a vaccine to SA-MCF. However, this formulation provided only limited protection in bison. Since bison is highly susceptible to MCF and the primary target for vaccine development, additional studies are necessary to evaluate new vaccine formulations and alternative OvHV-2 challenge methods in bison. In future trials, groups of bison will be vaccinated, while others will serve as non-vaccinated control and at designated time points post-immunization, animals will be challenged with OvHV-2, by either nebulization of a known amount of virus or by exposure to infected sheep, to assess vaccine efficacy. The trials will be conducted at the bison facilities of the University of Wyoming. The collaborator will assist with animal management, including inoculations, sample collection, euthanasia, necropsies, and pathological examinations. ARS will contribute financially to acquiring experimental animals, supply immunogens and challenge virus stocks, and assist with sample collection and processing. Data analysis and resulting publications will be jointly shared between the parties. Upon completion of the study, we anticipate a significant advancement in the development of a vaccine to protect susceptible species from SA-MCF.