A novel alphaherpesvirus and concurrent respiratory cryptococcosis in a captive koala (Phascolarctos cinereus)

Abstract

A novel alphaherpesvirus was detected in a captive adult, lactating, female koala (Phascolarctos cinereus) admitted to James Cook University Veterinary Emergency Teaching & Clinical Hospital in March 2019, showing signs of anorexia and severe respiratory disease. Postmortem examination revealed gross pathology indicative of pneumonia. Histopathology demonstrated a chronic interstitial pneumonia, multifocal necrotising adrenalitis and hepatitis. Intranuclear inclusion bodies were detected by light microscopy in the respiratory epithelium of the bronchi, bronchioles, alveoli, and hepatocytes, biliary epithelium and adrenal gland associated with foci of necrosis. Cryptococcus gattii was isolated from fresh lung on necropsy, positively identified by PCR, and detected histologically by light microscopy, only in the lung tissue. A universal viral family-level PCR indicated that the virus was a member of the Herpesviruses. Sequence analysis in comparison to other known and published herpesviruses, indicated the virus was a novel alphaherpesvirus, with 97% nucleotide identity to macropodid alphaherpesvirus 1. We provisionally name the novel virus phascolarctid alphaherpesvirus 3 (PhaHV-3). Further research is needed to determine the distribution of this novel alphaherpesvirus in koala populations and establish associations with disease in this host species.