Rift Valley fever virus (RVFV) is a mosquito-borne virus in the family Bunyaviridae that has spread throughout continental Africa to Madagascar and the Arabian Peninsula. The establishment of RVFV in North America would have serious consequences for human and animal health in addition to a significant economic impact on the livestock industry. Specific objectives of this thesis are to identify high-risk regions involved in RVFV importation to the U.S., evaluate pathways of introduction, and theoretically quantify the relative importance of local vectors and vertebrate hosts to RVFV transmission should the virus reach the U.S.
To estimate the relative risk of RVFV introduction to the U.S., the number of infectious mosquitoes arriving in the U.S. was quantified for five pathways: infected mosquitoes arriving by airplane, infected mosquitoes arriving by boat, infected mosquitoes arriving through tire trade, infected humans arriving by flight, and the trade of infected mammals. Results suggest that mosquito transport by airplane, mosquito transport by ship, and human travel are important pathways for RVFV introduction to the U.S. New York, Houston, Washington D.C., and Atlanta are high-risk regions for RVFV introduction in the U.S. Further, Saudi Arabia, South Africa, Nigeria, Egypt, Senegal, Ethiopia, Yemen and Angola are identified as regions at-risk for importing RVFV to the U.S.
Published and unpublished data on RVFV vector competence, vertebrate host competence, and mosquito feeding patterns from the United States were combined to quantitatively implicate mosquito vectors and vertebrate hosts that may be important to RVFV transmission in the United States. A viremia-vector competence relationship based on published mosquito transmission studies was used to calculate a vertebrate host competence index which was then combined with mosquito blood feeding patterns to approximate the relative contribution of a mosquito or vertebrate host to RVFV transmission. Results implicate several Aedes spp. mosquitoes and vertebrates in the order Artiodactyla as important hosts for RVFV transmission in the U.S. Moreover, this study identifies critical gaps in knowledge necessary to comprehensively evaluate the different contributions of mosquitoes and vertebrates to potential RVFV transmission in the U.S.
- Hamer, Gabriel Associate Professor