Metagenomic discovery and co-infection of diverse wobbly possum disease viruses and a novel hepacivirus in Australian brushtail possums

Wei-Shan Chang,Mang Shi,Edward C. Holmes,William J. Hartley,Karrie Rose,John-Sebastian Eden

doi:10.1186/s42522-019-0006-x

Abstract

BackgroundAustralian brushtail possums (Trichosurus vulpecula) are an introduced pest species in New Zealand, but native to Australia where they are protected for biodiversity conservation. Wobbly possum disease (WPD) is a fatal neurological disease of Australian brushtail possums described in New Zealand populations that has been associated with infection by the arterivirus (Arteriviridae) wobbly possum disease virus (WPDV-NZ). Clinically, WPD-infected possums present with chronic meningoencephalitis, choroiditis and multifocal neurological symptoms including ataxia, incoordination, and abnormal gait.MethodsWe conducted a retrospective investigation to characterise WPD in native Australian brushtail possums, and used a bulk meta-transcriptomic approach (i.e. total RNA-sequencing) to investigate its potential viral aetiology. PCR assays were developed for case diagnosis and full genome recovery in the face of extensive genetic variation.ResultsWe identified genetically distinct lineages of arteriviruses from archival tissues of WPD-infected possums in Australia, termed wobbly possum disease virus AU1 and AU2. Phylogenetically, WPDV-AU1 and WPDV-AU2 shared only ~ 70% nucleotide similarity to each other and the WPDV-NZ strain, suggestive of a relatively ancient divergence. Notably, we also identified a novel and divergent hepacivirus (Flaviviridae) - the first in a marsupial - in both WPD-infected and uninfected possums, indicative of virus co-infection.ConclusionsWe have identified marsupial-specific lineages of arteriviruses in mainland Australia that are genetically distinct from that in New Zealand, in some cases co-infecting animals with a novel hepacivirus. Our study provides new insight into the hidden genetic diversity of arteriviruses, the capacity for virus co-infection, and highlights the utility of meta-transcriptomics for disease investigation in a One Health context.

Highlights

Australian brushtail possums (Trichosurus vulpecula) are an introduced pest species in New Zealand, but native to Australia where they are protected for biodiversity conservation
We review archived Australian cases of Wobbly possum disease (WPD) to build a more robust syndrome description and, where frozen tissues were available, applied total RNA sequencing (“meta-transcriptomics”) to determine the infectious aetiology and potential origins of WPD in mainland Australian possums, in comparison with syndromes and agents previously identified in animals from New Zealand
Clinical and histological description of Australian wobbly possum disease virus cases Signalment, gross and histopathology data were collated from 474 brushtail possums, 49 of which fit the syndrome description for WPD

Summary

Introduction

Australian brushtail possums (Trichosurus vulpecula) are an introduced pest species in New Zealand, but native to Australia where they are protected for biodiversity conservation. Common and widely distributed across Australia, the brushtail possum (Trichosurus vulpecula) is protected under conservation legislation. It is a highly successful invasive vertebrate pest in New Zealand, where it was introduced from Tasmania in the 1830s to build a local fur industry [5]. The species rapidly adapted to the natural environment of New Zealand, causing devastating destruction of native forests and wildlife. Brushtail possums in New Zealand are estimated to cause $NZ35M/year in agricultural losses and the shared costs of attempted control exceed $100 M/year (https://predatorfreenz.org/resources/introduced-predator-facts/possumfacts/)

Methods

Results

Discussion

Conclusion