Evolutionary Comparisons of Chelonid Alphaherpesvirus 5 (ChHV5) Genomes from Fibropapillomatosis-Afflicted Green (Chelonia mydas), Olive Ridley (Lepidochelys olivacea) and Kemp’s Ridley (Lepidochelys kempii) Sea Turtles

Abstract

The spreading global sea turtle fibropapillomatosis (FP) epizootic is threatening some of Earth’s ancient reptiles, adding to the plethora of threats faced by these keystone species. Understanding this neoplastic disease and its likely aetiological pathogen, chelonid alphaherpesvirus 5 (ChHV5), is crucial to understand how the disease impacts sea turtle populations and species and the future trajectory of disease incidence. We generated 20 ChHV5 genomes, from three sea turtle species, to better understand the viral variant diversity and gene evolution of this oncogenic virus. We revealed previously underappreciated genetic diversity within this virus (with an average of 2035 single nucleotide polymorphisms (SNPs), 1.54% of the ChHV5 genome) and identified genes under the strongest evolutionary pressure. Furthermore, we investigated the phylogeny of ChHV5 at both genome and gene level, confirming the propensity of the virus to be interspecific, with related variants able to infect multiple sea turtle species. Finally, we revealed unexpected intra-host diversity, with up to 0.15% of the viral genome varying between ChHV5 genomes isolated from different tumours concurrently arising within the same individual. These findings offer important insights into ChHV5 biology and provide genomic resources for this oncogenic virus.

Microbial composition of carapace, feces, and water column in captive juvenile green sea turtles with carapacial ulcers

“…To date, there have been many microbiological studies on sea turtles. Several studies have demonstrated that Chelonid Alphaherpes virus 5 (ChHV5) causes fibropapillomatosis (FP) in the head and extremities of sea turtles, which can lead to restricted movement and reduced feeding ability ( 8 – 10 ). Previous studies have shown that environmental pollution, while correlated with habitat destruction, has no impact on ChHV5.…”

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

“…ChHV5 consensus genome generation from sand eDNA and phylogenetic analysis was conducted as previously described in Whitmore et al (2021), for the sample with sufficient ChHV5 aligning reads (patient "Archie").…”

Threats and Vulnerabilities for the Globally Distributed Olive Ridley (Lepidochelys olivacea) Sea Turtle: A Historical and Current Status Evaluation

“…Fibropapilloma tumours have been also observed in olive ridleys nesting on the Pacific coasts of Costa Rica [ 109 , 113 ], in “La Escobilla” sanctuary in Oaxaca, Mexico [ 114 ], in Nicaragua [ 115 ], in India [ 116 ], and foraging off the Pacific coast of Mexico [ 117 , 118 ]. Recently, FP has been reported in olive ridleys stranded in Chile [ 119 ] and in the U.S. [ 106 , 120 ]. Reports and sightings of olive ridley turtles with FP in Pacific and Atlantic waters, as well as nesting beaches, are becoming more and more frequent.…”