Livestock Challenge Models of Rift Valley Fever for Agricultural Vaccine Testing.

Andrea Louise Kroeker,William C Wilson,Shawn Babiuk,Juergen A Richt,Bradley S Pickering

doi:10.3389/fvets.2020.00238

Abstract

Since the discovery of Rift Valley Fever virus (RVFV) in Kenya in 1930, the virus has become widespread throughout most of Africa and is characterized by sporadic outbreaks. A mosquito-borne pathogen, RVFV is poised to move beyond the African continent and the Middle East and emerge in Europe and Asia. There is a risk that RVFV could also appear in the Americas, similar to the West Nile virus. In light of this potential threat, multiple studies have been undertaken to establish international surveillance programs and diagnostic tools, develop models of transmission dynamics and risk factors for infection, and to develop a variety of vaccines as countermeasures. Furthermore, considerable efforts to establish reliable challenge models of Rift Valley fever virus have been made and platforms for testing potential vaccines and therapeutics in target species have been established. This review emphasizes the progress and insights from a North American perspective to establish challenge models in target livestock such as cattle, sheep, and goats in comparisons to other researchers' reports. A brief summary of the potential role of wildlife, such as buffalo and white-tailed deer as reservoir species will also be discussed.

Highlights

In the last 20 years there has been a re-emergence of various well-known arboviral diseases, many of which are zoonotic in nature, such as West Nile, Japanese encephalitis, Rift Valley fever, Venezuelan equine encephalitis, and Eastern equine encephalitis [1]
Initial experimental goat infection studies were performed with RVF virus (RVFV) strain ZH501 [112] and were intended to establish the dose required for the induction of viremia, the timing of viremia and a comparison of inoculation virus grown in mammalian and insect cells
We proposed that the p78 present in virions of mosquito-grown viruses may function as a type I interferon antagonist, which may allow for a productive infection of initial target cells [58], as was shown earlier for alphaviruses [145]. (d) Route of inoculation: In addition to the experimental infections performed at NCFAD and Kansas State University (KSU), other studies have shown that viremia can be induced by a wide variety of different routes including intramuscular (IM), intravenous (IV), intraperitoneal (IP), intracerebral (IC), subcutaneous (SQ), conjunctival, and oral inoculations [112, 137, 147,148,149]

Summary

Introduction

AND INTRODUCTIONIn the last 20 years there has been a re-emergence of various well-known arboviral diseases, many of which are zoonotic in nature, such as West Nile, Japanese encephalitis, Rift Valley fever, Venezuelan equine encephalitis, and Eastern equine encephalitis [1]. The challenge controls in these studies developed peracute clinical signs and fever, viremia for 4–6 days with peak titers of 105-106 TCID50, and virus was detected in the liver. Other groups have developed 2–3 month old challenge models with the 56/74 RVFV isolate in Ripolessa [107, 109], Colmenarena [110] and other [111] sheep breeds using subcutaneous inoculation at 105-106 TCID50.

Results

Conclusion