The Concurrent Detection of Chelonid Alphaherpesvirus 5 and Chelonia mydas Papillomavirus 1 in Tumoured and Non-Tumoured Green Turtles

Abstract

Characterised by benign tumours, fibropapillomatosis (FP) is a debilitating disease that predominantly afflicts the endangered green turtle (Chelonia mydas). A growing body of histological and molecular evidence has associated FP tumours with Chelonid alphaherpesvirus 5 (ChHV5). However, a recent study which detected both ChHV5 and Chelonia mydas papillomavirus 1 (CmPV1) DNA in FP tumour tissues has challenged this hypothesis. The present study aimed to establish a probe-based qPCR to assess the wider prevalence of CmPV1 and co-occurrence with ChHV5 in 275 marine turtles foraging in waters adjacent to the east coast of Queensland, Australia: three categories: Group A (FP tumours), Group B (non-tumoured skin from FP turtles) and Group C (non-tumoured skin from turtles without FP). Concurrent detection of ChHV5 and CmPV1 DNA is reported for all three categories, where Group A had the highest rate (43.5%). ChHV5 viral loads in Group A were significantly higher than loads seen in Group B and C. This was not the case for CmPV1 where the loads in Group B were highest, followed by Group A. However, the mean CmPV1 load for Group A samples was not significantly different to the mean load reported from Group B or C samples. Collectively, these results pivot the way we think about FP; as an infectious disease where two separate viruses may be at play.

Revealing the uncharacterised diversity of amphibian and reptile viruses

“…Bellinger river nidovirus, bearded dragon circovirus and chaphamaparvoviruses were all characterised after severe mortality events in reptiles [ 10 , 12 ]. Diseases are frequently associated with coinfections and may be attributed to complex interactions between multiple pathogens [ 48 ], as in the case of tumours in green turtles [ 49 ]. As so little is known about the frequency, distribution and diversity of viruses, it is hard to assess the risk that novel viruses pose.…”

Genotype data not consistent with clonal transmission of sea turtle fibropapillomatosis or goldfish schwannoma

“…ChHV5 has been detected in the tank water of FP-afflicted green sea turtles, and FP-afflicted turtles exhibiting weaker immune activation had worse clinical outcomes 37 , 63 . Recently, green sea turtle papillomavirus 1 (CmPV1) was reported in 47% of FP tumours analysed, suggesting the potential of multiple viruses as cofactors in FP disease 64 . It is also interesting to note that FP lesions, along with concurrent ChHV5 infection, have been reported in the eastern box turtle ( Terrapene carolina ), a terrestrial turtle species 65 .…”

Detection and population genomics of sea turtle species via noninvasive environmental DNA analysis of nesting beach sand tracks and oceanic water

“…The qPCR reaction mixtures were performed in a total volume of 10 µl: 5 µl TaqMan Fast Advanced Master Mix (Fisher Scientific cat no: 4444557); 3 µl Nuclease free water (Fisher Scientific); 1 µl ChHV5 DPol. (Mashkour et al, 2021) or custom C. mydas 16S rRNA or custom C. caretta 16S rRNA (Table S3) 5 µM primer/probe stock (final concentration of 0.5 µM of each primer/probe); 1 µl DNA template, per well of a 384-well plate.…”