Emerging viral disease is a significant concern, with potential consequences for human, animal and environmental health. Over the past several decades, multiple novel viruses have been found in wildlife species, including reptiles, and often pose a major threat to vulnerable species. However, whilst a large number of viruses have been described in turtles, information on poxvirus in cheloniids remains scarce, with no molecular sequence data available to date. This study characterizes, for the first time, a novel poxvirus, here tentatively designated cheloniid poxvirus 1 (ChePV-1). The affected cutaneous tissue, recovered from a green sea turtle (Chelonia mydas) captured off the Central Queensland coast of Australia, underwent histological examination, transmission electron microscopy (TEM), DNA extraction and genomic sequencing. The novel ChePV-1 was shown to be significantly divergent from other known poxviruses and showed the highest sequence similarity (89.3%) to avipoxviruses (shearwater poxvirus 2 (SWPV2)). This suggests the novel ChePV-1 may have originated from a common ancestor that diverged from an avipoxvirus-like progenitor. The genome contained three predicted unique genes and a further 15 genes being truncated/fragmented compared to SWPV2. This is the first comprehensive study that demonstrates evidence of poxvirus infection in a marine turtle species, as well as a rare example of an avipoxvirus crossing the avian-host barrier. This finding warrants further investigations into poxvirus infections between species in close physical proximity, as well as in vitro and in vivo studies of pathogenesis and disease.

As part of a sea turtle health monitoring program on the central east coast of Queensland, Australia, stranded and sick green sea turtles (Chelonia mydas) were subjected to necropsy and histopathology. A subset of these turtles had myocarditis of varying severity, which could not be attributed to parasitism by spirorchid flukes or bacterial infections. We, therefore, undertook an investigation to determine whether virus infections might be part of the pathogenesis. Deep sequencing revealed abundant DNA virus contigs in the heart tissue, of which CRESS and circoviruses appeared to be the most consistently present. Further analysis revealed the homology of some of the circoviruses to the beak and feather disease virus. While a causative link to myocarditis could not be established, the presence of these viruses may play a contributing role by affecting the immune system and overall health of animals exposed to pollutants, higher water temperatures, and decreasing nutrition.