Establishment of a Zebrafish Infection Model for the Study of Wild- Type and Recombinant European Sheatfish Virus

Amphibian-like ranaviruses include pathogens of fish, amphibians, and reptiles that have recently evolved from a fish-infecting ancestor. The molecular determinants of host range and virulence in this group are largely unknown, and currently fish infection models are lacking. We show that European sheatfish virus (ESV) can productively infect zebrafish, causing a lethal pathology, and describe a method for the generation of recombinant ESV, establishing a useful model for the study of fish ranavirus infections. Amphibian-like ranaviruses (ALRVs) are a subgroup of closelyrelated viruses within the genus Ranavirus isolated from dif-ferent amphibian, reptile, and fish host species (1). Epizootic he-matopoietic necrosis virus (EHNV), a rainbow trout pathogen belonging to the ALRV found exclusively in Australia, was the first ALRV isolated from fish to be completely sequenced (2). More recently, we obtained the complete genome of a second fish ALRV isolated from European sheatfish (ESV) (3). Both the dot plot analyses as well as a phylogenetic tree, including completely se-quenced vertebrate ranaviruses (Fig. 1), confirm that ESV is very closely related to EHNV, with the short branch length amon