Technical Abstract: The vulnerability of US livestock to introduction of exotic insect-transmitted pathogens is recognized as a major threat to U.S. agriculture. Rift Valley Fever virus (RVFv) is rated the highest threat to animal agriculture in the Americas based on economic and public health implications, the availability of diagnostic, preventive, and control options, and current status of agent-and disease related research. This presentation summarizes: 1) predicted impacts associated with introduction of Rift Valley Fever virus (RVFv) into the U.S., and 2) research concerning the use of synthetic pyrethroid compounds for their 'repellency activity' in protecting livestock from insect blood feeding and pathogen transmission. Synthetic pyrethroid insecticides are widely used for controlling insects associated with livestock due to there high insect toxicity and low mammalian toxicity. In addition to insect toxicity, many synthetic pyrethroids have inherent properties (rapid effects on the insect nervous system) that irritate (excite) and/or repel insects. This effect, variously described as "host avoidance irritation" or "contact repellency" causes insects that contact a treated surface to depart before blood feeding, but has received little recognition as a means of protecting livestock from insect blood-feeding and transmission of pathogens. Given the vulnerability of U.S. livestock to exotic insect-transmitted pathogens, the potential for using pyrethroid insecticides as repellents to suppress insect feeding assumes a new importance. Especially strategic is protection from insect feeding during the interval between vaccination and development of protective antibodies, particularly for animals that amplify a pathogen to levels infectious for other insects, thus blocking further spread of a pathogen.