Location: Foreign Arthropod Borne Animal Disease Research
Project Number: 3022-32000-024-017-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jun 1, 2024
End Date: May 31, 2025
Objective:
Rift Valley fever (RVFV) primary control method is the use of attenuated vaccination programs. The long-term protection afforded by these vaccinations in not known. The objective of this project is to determine if a single RVFV attenuated vaccination (Smithburn strain) has the potential to induce and sustain lifelong immunity in sheep in a field setting without boosting through natural infection. Importantly, this would be the first evidence to suggest that only a single vaccine dose in weaned lambs would be suffcient to provide immunity against RVFV for the duration of that individual’s productive lifespan.
Approach:
This project will assess the RVFV long-term efficacy of modified live attenuated vaccinated adult ewes, as well as unvaccinated control sheep that were enrolled in a previous vaccine study. Adult sheep will be challenged using a proven virulent RVFV established infection model and evaluated daily for clinical signs, including abortion, and viremia. Animals showing clinical disease will be euthanized if they reach clearly defined humane endpoints. Surviving animals will be monitored for 2-3 weeks post-challenge, during which regular serum samples will be collected for PCR and serology including virus neutralization test (VNT). At the end of the follow-up period all animals will be euthanized and subjected to necropsy and detailed histopathological and immunohistochemical examination to determine presence and extent of RVFV in tissues, including placenta and fetus.
