1a.Objectives (from AD-416):
The long term goal of this project is the development of rapid, reliable, and sensitive diagnostic assays for Rift Valley fever that are suitable for use in Differentiate Infected from Vaccinated Animal control strategies. The main objectives are: (1) determine the optimal time points post infection and diagnostic samples (blood, saliva etc.), for detection of RVFV with these assays; and (2) evaluate the compatibility of these assays with a DIVA control strategy which will be determined by comparing the diagnostic results of vaccinated sheep with wild-type infected sheep. These studies may include evaluating the ability of diagnostic assays to detect infectious virus, viral antigen(s) and virus-specific nucleic acids in insects.
1b.Approach (from AD-416):
The National Veterinary Stockpile Recommendations list Rift Valley Fever (RVF) as the third most important agricultural threat to U.S. livestock. There are limited diagnostic assays available, and no RVF vaccines that are licensed for use in the U.S. Early and sensitive detection of an introduction of RVF is critical for an effective control and eradication strategy. The USDA, ARS, Arthropod-Borne Animal Diseases Research Unit (ABADRU), is developing diagnostic reagents for eventual distribution to the National Animal Health Laboratory Network (NAHLN). The RVF diagnostic reagents have to be safe and compatible with a Differentiate Infected from Vaccinated Animal (DIVA) control strategy and must work for both vertebrate hosts and invertebrate vectors.
The specific objective of this project is the development of rapid reliable and sensitive diagnostic assays to differentiate an infected from vaccinated animal (DIVA). The baculovirus system has been used to express RVFV proteins that have been purified and shown to be immunologically reactive. These proteins have produced in large quantities and assays are being optimized in preparation for laboratory and field evaluation.