Ranavirus Distribution and Host Range

Abstract

Ranaviruses are globally distributed pathogens in amphibian, fish, and reptile communities that appear to be emerging. Cases of ranavirus infection or disease have been confirmed in at least 177 amphibian species (25 families), 49 fish species (25 families), and 37 reptile species (17 families). Transmission of individual strains between animal classes has been documented. While ranaviruses are frequently associated with mass die-offs, host susceptibility differs among species, with some species harboring subclinical infections and likely serving as reservoirs for the virus and other highly susceptible species amplifying the virus. Currently, there are seven recognized species of ranavirus, with stark differences in pathogenicity between strains and hosts. Several strains among these species have been named, and changes in taxonomy in this genus can lead to some confusion. Frog virus 3 is the best studied species of the genus Ranavirus and appears to be the most globally distributed species, with viruses of this species infecting ectothermic vertebrates across three vertebrate classes. International commerce involving infected ectothermic vertebrates undoubtedly has contributed to the global distribution, diversity, and emergence of ranaviruses. Herein, we describe the global distribution of ranaviruses in amphibians, fish, and reptiles, host range of the different Ranavirus species, the implications of interclass transmission, and the impact of trade on ranavirus distribution. The Global Ranavirus Reporting System (GRRS), which documents global detections of ranaviruses, is also presented.