Chelonid alphaherpesvirus 5 qPCR of archived blood and skin samples underpredicts infections in juvenile green turtles Chelonia mydas.

Chelonid alphaherpesvirus 5 (ChHV5) is the putative pathogen of fibropapillomatosis, a tumor-forming sea turtle disease. Quantitative polymerase chain reaction (qPCR) techniques are commonly applied to evaluate the presence and quantity of ChHV5 in blood and tissue samples. However, samples can have little or no virus present despite coming from infected individuals. In addition, sample age and storage may further impact ChHV5 detection. This creates uncertainty in the interpretation of ChHV5 qPCR results for archived (>1 yr old) blood and skin because a negative sample does not imply an individual was free of ChHV5 infection, but rather that the sample itself was free of viable ChHV5 DNA. To assess the ability of qPCR to detect ChHV5 infections from archived samples, we tested blood, skin, and tumor samples collected from juvenile green turtles Chelonia mydas captured in the Indian River Lagoon, Florida, USA, between 1995 and 2018. Sample ages ranged from 1 to 24 yr old at the time of molecular analyses. We found very low overall prevalence of ChHV5 in blood (1.4% positive, n = 513) and skin (6.5% positive, n = 123) samples, and high prevalence in tumor samples (89.7% positive, n = 39). These results suggest that qPCR of archived blood and/or skin samples provides little inference on individual-level infection status.