Prevalence and Clinical Significance of Herpesvirus Infection in Populations of Australian Marsupials

Abstract

Herpesviruses have been reported in several marsupial species, but molecular classification has been limited to four herpesviruses in macropodids, a gammaherpesvirus in two antechinus species (Antechinus flavipes and Antechinus agilis), a gammaherpesvirus in a potoroid, the eastern bettong (Bettongia gaimardi) and two gammaherpesviruses in koalas (Phascolarctos cinereus). In this study we examined a range of Australian marsupials for the presence of herpesviruses using molecular and serological techniques, and also assessed risk factors associated with herpesvirus infection. Our study population included 99 koalas (Phascolarctos cinereus), 96 eastern grey kangaroos (Macropus giganteus), 50 Tasmanian devils (Sarcophilus harrisii) and 33 common wombats (Vombatus ursinius). In total, six novel herpesviruses (one alphaherpesvirus and five gammaherpesviruses) were identified in various host species. The overall prevalence of detection of herpesvirus DNA in our study population was 27.2% (95% confidence interval (CI) of 22.6–32.2%), but this varied between species and reached as high as 45.4% (95% CI 28.1–63.7%) in common wombats. Serum antibodies to two closely related macropodid herpesviruses (macropodid herpesvirus 1 and 2) were detected in 44.3% (95% CI 33.1–55.9%) of animals tested. This also varied between species and was as high as 92% (95% CI 74.0–99.0%) in eastern grey kangaroos. A number of epidemiological variables were identified as positive predictors for the presence of herpesvirus DNA in the marsupial samples evaluated. The most striking association was observed in koalas, where the presence of Chlamydia pecorum DNA was strongly associated with the presence of herpesvirus DNA (Odds Ratio = 60, 95% CI 12.1–297.8). Our results demonstrate the common presence of herpesviruses in Australian marsupials and provide directions for future research.

Identification of unusual Chlamydia pecorum genotypes in Victorian koalas (Phascolarctos cinereus) and clinical variables associated with infection

“…However, there were still a large number of koalas with evidence of reproductive tract pathology where qPCR did not detect C. pecorum (26/45), suggesting other aetiological agent(s) may be present that should also be considered in conservation programs. Signs of disease due to other pathogens, such as koala herpesvirus (Stalder et al, 2015) or koala retrovirus (Denner, 2014), could also overlap with C. pecorum infection. Comprehensive investigations into these and other pathogens may also further our understanding of the true significance of C. pecorum in Victorian koalas.…”

Detection and Differentiation of Two Koala Gammaherpesviruses by Use of High-Resolution Melt (HRM) Analysis Reveals Differences in Viral Prevalence and Clinical Associations in a Large Study of Free-Ranging Koalas

“…and PCR assays followed by amplicon cloning and sequencing (9)(10)(11). Serum virus neutralization assays have not been performed for detection of antibodies to PhaHV-1 and -2, which are limited by the lack of availability of cells suitable for virus propagation and may also be complicated by cross-neutralization of these viruses, which is common in herpesviruses (12,13).…”

“…PCR cloning and sequencing techniques are effective for the detection and differentiation of PhaHV-1 and -2, but the process is inefficient and costly for large-scale population studies, particularly when resources for investigation of infectious diseases in wildlife is limited. Thus, prior studies examining virus prevalence using direct amplicon sequencing are likely to have underestimated the prevalence of PhaHV-1 and PhaHV-2 within populations (11).…”

Characterisation of the faecal virome of captive and wild Tasmanian devils using virus-like particles metagenomics and meta-transcriptomics

“…Further analysis of the Gammaherpesvirinae phylogenetic structure based on the DNA polymerase showed that DaHV-3 forms a distinct lineage that is most closely related to Bovine gammaherpesvirus 6 and Common bottlenose dolphin gammaherpesvirus 1 strain Sarasota (Figure 5d). The previously characterised Dasyurid herpesvirus 2 (DaHV-2) isolated from Tasmanian devils [12] could not be included in the phylogenetic analysis because there are no available sequences from the same genomic regions. A BLASTx search of the DNA polymerase showed that DaHV-3 exhibited the greatest amino acid similarity (93.3%) with the previously characterised Macropodid herpesvirus 3(MaHV-3) [12], whose DNA polymerase amino acid sequence was also too short (<50% of the other representative herpesviruses) to be included in the phylogenetic analysis.…”

“…While extensive research has focused on DFTD itself as well as devil genetic diversity and susceptibility to the disease over the past decade [7-11], our understanding of other disease threats to devils remains limited. Specifically, virological studies are scarce and limited to the identification of a single gammaherpesvirus (DaHV-2), for which captivity was identified as a significant risk factor [12]. A comprehensive characterisation of the viral communities inhabiting the Tasmanian devil is an essential step to improving our understanding of host-microbe relationships, and maximising health and conservation management of the species.…”