Vector Potential Index: Bridging competence and contribution as an integrative measure of relative transmission capability

1. Vectorial capacity (VC) is a powerful tool for estimating a species’ importance in the transmission of vector-borne pathogens and predicting impacts of specific control measures on the transmission of those pathogens. However, VC is rarely estimated for zoonotic multi-vector, multi-host vector-borne disease (VBD) systems, due to the inherent difficulties of measuring several parameters, especially biting rate and daily probability of survival. 2. We present the Vector Potential Index (VPI), a novel metric for evaluating and comparing the potential of blood-feeding arthropod vectors to contribute to zoonotic VBD transmission using West Nile virus (WNV) in the eastern United States as a model system. Taking a meta-analysis approach, the VPI combines vector competence and host use data obtained from scientific literature to assign relative and absolute VPI ranks across species and transmission cycles. 3. Our case study of WNV demonstrates that the VPI framework effectively quantifies vector species’ potential to contribute to enzootic and epizootic transmission cycles. Most species exhibited low vector potential and although Aedes species were the most competent WNV vectors in the laboratory, only Culex species were assigned higher VPI ranks. Additionally, the VPI suggests that the contribution of Culex salinarius to WNV transmission in the U.S. may be greater than previously assumed based on assessments of individual parameters. Relative and absolute VPI ranks assigned to species aligned with recent work reviewing their role as vectors in the transmission cycles, indicating that by jointly considering vector competence and host use, the VPI provides a realistic approximation of a vector species’ potential to contribute to VBD transmission in the natural environment. 4. The VPI is a practical and highly versatile metric that is useful either as a stand-alone application or integrated with existing approaches, where it can be used to evaluate and compare vector species across different VBD systems or spatiotemporal scales at the species, population, or community level. We recommend the objective and reproducible VPI as a powerful yet simple tool for scientists and public health practitioners, where this trait-based approach has considerable potential to provide new insights into disease systems and enhance VBD surveillance and intervention strategies.