Multidecadal High Mortality Disease Events in Australian Domestic Geese Associated with a Novel Alphaherpesvirus, Designated Anatid Alphaherpevirus 2.

Herpesviruses are ubiquitous viruses which infect a wide range of hosts. Novel herpesviruses are being increasingly detected in free-ranging bird populations and there are growing concerns for cross-species infection and spillover events. Herein, multiple sporadic outbreaks of mortality caused by a herpesvirus are described in domestic geese in Queensland, Australia. Goose herpesvirus was initially detected in 1989 in south-east Queensland, and this article details four further recent outbreaks and reports novel genome sequencing and phylogeny of the preliminarily designated anatid alphaherpesvirus 2 (AnHV-2). Affected flocks were housed outdoors and comingled with other domesticated and wild anseriforms and other birds which were unaffected by disease. Affected geese displayed anorexia, lethargy, weakness, vomiting, and diarrhoea prior to death within 12-24 hr of the onset of clinical signs. Post-mortem examinations showed variable hepatic necrosis, splenic necrosis, fibrinonecrotising enteritis, lymphoid necrosis, necrotising thymitis, necrotising adrenalitis, and vasculitis. Intranuclear inclusion bodies were observed in hepatocytes, biliary epithelium, small intestinal mucosal epithelium, thymus, endothelial cells, ovarian stromal cells, adrenal cortical cells, and neuronal cell bodies in peripheral nerve ganglia. Transmission electron microscopy visualised herpesviral particles in virus culture supernatant, and within the nuclei of hepatocytes, biliary epithelium, and endothelial cells in case tissues. The genome sequence of this herpesvirus, designated anatid alphaherpesvirus 2 (AnHV-2), is described. While investigating goose mortalities, archived isolate from a swan with suspected herpesvirus infection was tested and genome sequencing identified a further novel herpesvirus, proposed anatid alphaherpesvirus 3 (AnHV-3). The AnHV-2 and AnHV-3 genomes were more similar to each other, with a nucleotide identity of 76.1%, than to reference genome sequences. Phylogenetically, the new genomes formed a distinct clade within the alphaherpesvirus genus Mardivirus. We sequenced four AnHV-2 genomes from different cases and these did not display consistent divergence over time or distance. Expanded surveillance and outbreak testing are recommended, facilitated by the development of a specific real-time PCR for the rapid detection of AnHV-2.