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.

Keywords: Chelonia mydas papillomavirus 1; Chelonid alphaherpesvirus 5; fibropapillomatosis; marine turtles; tumour.

Figure 1

The distribution of chelonid alphaherpesvirus 5 (ChHV5) and Chelonia mydas papillomavirus 1 (CmPV1) in FP tumour samples (Group A) collected from green turtles at six regions along the Queensland coast. A total of 131 FP tumour tissues were tested. Of the assay samples 62 reacted in the qPCR for CmPV1, 113 for ChHV5, and 12 samples did not react in either assay. 57 turmor samples reacted in both viruses. The viral detection at each site is categorised into three categories: ChHV5 only (red), CmPV1 only (green), both ChHV5 and CmPV1 detected in the same sample (beige). The total number of samples screened (n) and the total number of negatives (neg) are shown for each location.

Figure 2

Boxplots of ChHV5 viral loads (log scale) in different sample types from six regions of Queensland. Group A (FP Tumours), Group B (Non-tumoured skin from turtles with FP tumours) and Group C (Skin from non-tumoured turtles). The Box plots of viral loads include the median (centre horizontal line), interquartile range (box), minimum and maximum (whiskers), and outliers (diamonds).

Figure 3

Box-plots of CmPV1 viral loads (log scale) in different sample types from six regions of Queensland. Group A (FP Tumours), Group B (Non-tumoured skin from turtles with FP tumours) and Group C (Skin from non-tumoured turtles). The Box plots of viral loads include the median (centre horizontal line), interquartile range (box), minimum and maximum (whiskers), and outliers (diamonds).