Quantifying chelonid herpesvirus 5 in symptomatic and asymptomatic rehabilitating green sea turtles

Abstract

Fibropapillomatosis (FP), an infectious disease of sea turtles, is characterized by tumors of the skin, eye(s) and/or internal organ(s), and is associated with chelonid herpesvirus 5 (ChHV5). Despite extensive research on FP, the pathogenesis of ChHV5 remains poorly understood, particularly regarding asymptomatic infections. Here, we provide evidence for detectable ChHV5 DNA in biological samples from symptomatic and asymptomatic green turtles Chelonia mydas. Using a probe-based quantitative PCR (qPCR) assay for ChHV5, we evaluated the relationship between ChHV5 DNA loads and FP disease status, and investigated potential routes of ChHV5 shedding. Samples of tissue, blood, urine, and feces were collected from 67 green turtles at 3 rehabilitation facilities in the southeastern USA. Turtles were divided into 3 study groups: clinical signs of FP (n = 23), history of FP but no clinical signs (n = 13), and no known history of FP (n = 31). Via qPCR, ChHV5 DNA was reliably detected in FP tumors, non-tumored skin, blood, urine, cloacal swabs, and plasma from green turtles in all 3 groups. Our results provide novel evidence for ChHV5 DNA in blood cells, which may represent a critical phase of the ChHV5 life cycle and provide a mechanism for viral transport, and documents that viral DNA can be detected in the urine of symptomatic and asymptomatic turtles. As molecular diagnostics become more affordable, sea turtle health experts can use qPCR to monitor ChHV5 gene copies and thereby detect early signs of viral presence in blood, urine, and tissue samples.