Detection of macropodid alphaherpesvirus 2 infection and lesions in sudden death of a captive Virginia opossum and a water opossum

Abstract

Macropodid alphaherpesvirus 2 (MaAHV2) is best described in macropods and has been implicated in outbreaks among captive marsupial populations in Australia. Natural disease caused by herpesviruses has not been reported previously in opossum species, to our knowledge. One Virginia opossum ( Didelphis virginiana) and 1 water opossum ( Chironectes minimus) were submitted for postmortem examination from a zoo that housed 6 opossums, all of which died within several weeks. Red kangaroos ( Macropus rufus) and red-necked wallabies ( Macropus rufogriseus) were also present at the facility. Liver samples from both opossums were submitted for transmission electron microscopy and whole-genome sequencing. Microscopically, both opossums had multifocal necrosis in the liver and lung, with intranuclear inclusion bodies within hepatocytes and pneumocytes. Another significant finding in the Virginia opossum was sepsis, with isolation of Streptococcus didelphis from various organs. Ultrastructural analysis of formalin-fixed liver tissue identified herpesviral replication complexes in both opossums; negative-stain electron microscopy of unfixed liver tissue repeatedly yielded a negative result. The herpesvirus had >99% nucleotide identity with MaAHV2. These 2 cases indicate that both opossum species are susceptible to MaAHV2 infection, and the outbreak has implications for mixed-species facilities that house macropods.