Abstract

Rhabdoviruses possess bullet-shaped nucleocapsids enclosing the negative-sense single-stranded RNA genome that ranges in size from 10–16 kilobases. The family Rhabdoviridae within the order Mononegavirales includes 18 genera and 131 known species that infect plants, arthropods, and vertebrates including fish, reptiles, birds, and mammals. They are responsible for noteworthy diseases in human and veterinary medicine including rabies. To date, only a single report characterizing a rhabdovirus from a cetacean has appeared involving a white-beaked dolphin (Lagenorhynchus albirostris) that stranded along the coast of the Netherlands in 1992.¹ In 2017, an adult male harbor porpoise (Phocoena phocoena) stranded off the coast of Alaska and displayed scattered, mild ulcerative dermatitis, and necrotizing balanoposthitis. Body condition was poor and the lung, liver, subcutaneous tissues, and gastrointestinal tract were heavily parasitized. Histopathologic findings from the skin lesions included pustular epidermitis and dermatitis, with epithelial cell hydropic and ballooning degeneration. Occasional intracytoplasmic eosinophilic inclusion bodies were present. There was a necroulcerative subacute balanoposthitis. Skin and penile swabs were processed for virus isolation resulting in cytopathic effect on both primary beluga whale kidney (BWK) and Vero cells. Transmission electron microscopy revealed abundant bullet-shaped nucleocapsids within the cytoplasm of BWK cells consistent with a rhabdovirus. A cDNA library was prepared using RNA extracted from the infected BWK supernatant and sequenced on an Illumina MiSeq sequencer. The de novo assembly of 2,607,928 paired-end reads using SPAdes genome assembler recovered the near complete genome of a novel rhabdovirus, the harbor porpoise rhabdovirus (PRV), that was completed by PCR and Sanger sequencing. Maximum Likelihood phylogenetic analysis based on the L gene revealed the PRV branches as the sister group to the white-beaked dolphin rhabdovirus (DRV). The cetacean rhabdovirus clade (PRV and DRV) was found to be nested within the genus Perhabdovirus which includes finfish rhabdoviruses. These data are consistent with a previous hypothesis¹ that cetacean rhabdoviruses arose following a jump from a finfish host.

* Presenting author

Literature Cited

1.  Siegers JY, van de Bildt M, van Elk CE, Schürch AC, Tordo N, Kuiken T, Bodewes R, Osterhaus ADME. 2014. Genetic relatedness of dolphin rhabdovirus with fish rhabdoviruses. Emerging Infectious Diseases. 20:1081–1082.