Abstract

Polar bears under managed care can be exposed to and contract infection with novel opportunistic pathogens not present in their natural environment.^1,2 A 4-month-old polar bear (Ursus maritimus) living in an isolated enclosure with his mother in Tierpark Berlin, Germany, was suffering from diarrhea and loss of appetite and died in early 2017. Histopathology revealed severe hepatic degeneration and necrosis without evidence of inflammation or viral inclusion bodies. Pathogen nucleic acids were sought from liver, kidney, small intestine and lymph node tissue by high throughput sequencing (HTS) after RNA and DNA extraction. A novel Mastadenovirus was identified, and a nearly complete genome was assembled from the sequences. Viral DNA concentration was highest in blood as determined by quantitative PCR (qPCR) suggesting virus tropism for white blood cells. Positive immunofluorescence staining of virus cultured on several mammalian cell lines highlighted that the virus was able to replicate in the kidney cells during early passage, but virus propagation could not be sustained. Phylogenetic analysis demonstrated that the virus is highly divergent from other previously identified Mastadenovirus species and in most analyses is basal to known viral groups. Additional polar bear individuals were tested for the presence of the discovered virus and were all negative. It is therefore likely that the polar bear was infected from an unknown reservoir in or near its enclosure, illustrating that adenoviral diversity remains largely uncharacterized.

Literature Cited

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