Evolutionary Evidence for Multi-host Transmission of Cetacean Morbillivirus

Cetacean morbillivirus (CeMV) has emerged as the pathogen which poses the greatest risk for triggering epizootics in dolphin and whale populations worldwide, and has a high propensity for interspecies transmission, including sporadic infection of seals. In this study, we investigated the evolutionary history of CeMV by deep sequencing wild-type viruses from tissue samples representing cetacean species with different spatio-temporal origins. Bayesian phylogeographic analysis generated an estimated evolutionary rate of 2.34x10-4 nucleotide substitutions/site/year and showed that CeMV evolutionary dynamics is neither host- nor location-restricted. Moreover, the dolphin morbillivirus strain of CeMV has undergone purifying selection without evidence of species-specific mutations. Cell-to-cell fusion and growth kinetics assays demonstrated that CeMV can use both dolphin and seal CD150 as a cellular receptor. Thus, it appears that CeMV can readily spread among multiple cetacean populations and may pose an additional spillover risk to seals.