Location: Arthropod-borne Animal Diseases ResearchTitle: Development of a Rift Valley fever virus viremia challenge model in sheep and goats) Author
Submitted to: Vaccine
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/12/2014
Publication Date: 3/12/2014
Citation: Weingartl, H.M., Nfon, C.K., Miller, M.M., Wilson, W.C. 2014. Development of a Rift Valley fever virus viremia challenge model in sheep and goats. Vaccine. 32:2337–2344. DOI: 10.1016/j.vaccine.2014.02.066. Interpretive Summary: The study describes the development of a new easier to conduct infection model for evaluation of vaccines for the mosquito-borne virus Rift Valley fever, which causes severe to lethal disease in domestic ruminants and man. The disease is endemic is Sub-Saharan Africa and could be accidentally introduced into non-endemic countries. Current challenge models are useful but are complicated to perform in the required high biological secure facilities because they require synchronized pregnant animals.
Technical Abstract: Rift valley fever virus (RVFV), a member of the family Bunyaviridae, causes severe to fatal disease in newborn ruminants, as well as abortions in pregnant animals; both preventable by vaccination. Availability of a challenge model is a pre-requisite for vaccine efficacy trials. Several modes of inoculation with RVFV ZH501 were tested on goats and sheep. Although all inoculated animals developed viremia based on RNA detection, differences in terms of infectious viremia were observed between using inoculum produced in mosquito C6/36 cells compared to Vero E6 cell-produced inoculum. Only C6/36-RVFV inoculation led to development of viremia in all inoculated sheep and goats. The C6/36 cell- produced RVFV appears to be more infectious with earlier onset of viremia, especially in sheep, and may also more closely represent a field situation. Goats were somewhat more resistant to the disease development with lower and shorter infectious virus viremia, and with only some animals developing transient increase in rectal temperature in contrast to sheep. In conclusion, a challenge protocol suitable for goat and sheep vaccine efficacy studies was developed using subcutaneous inoculation of 10^7 PFU per animal with RVFV ZH501 produced in C6/36 cells.