Occurrence of Fibropapillomatosis in Green Turtles (Chelonia mydas) in Relation to Environmental Changes in Coastal Ecosystems in Texas and Florida: A Retrospective Study.

Abstract

Simple SummaryIn the last few decades, sea turtles have been threatened by a disease called Fibropapillomatosis. Infection causes the growth of several tumors which can prevent affected turtles from seeing, swimming, and feeding properly, often with lethal outcomes. Fibropapillomatosis was described for the first time in Florida in 1938 and has since then increased and spread worldwide. To this day, there is no strong nor clear evidence on what causes the exacerbation of this disease which is associated with a herpesvirus. There is a consensus, however, that human-driven changes in the sea turtle habitats (i.e., climate change, pollution, urbanization) might play a role in increasing the number and severity of clinical cases. This study intends to explore the role of various possible environmental drivers behind the increased occurrence of this disease. We found that sea temperature, salinity, human population density, and river discharge from the coastline could be important drivers of tumor prevalence. Results from this preliminary work have the potential to offer an important baseline for future research on environmental drivers of Fibropapillomatosis. Fibropapillomatosis is a neoplastic disease of marine turtles, with green turtles (Chelonia mydas) being the most affected species. Fibropapillomatosis causes debilitating tumor growths on soft tissues and internal organs, often with lethal consequences. Disease incidence has been increasing in the last few decades and the reason is still uncertain. The potential viral infectious agent of Fibropapillomatosis, chelonid herpesvirus 5, has been co-evolving with its sea turtle host for millions of years and no major mutation linked with increased disease occurrence has been detected. Hence, frequent outbreaks in recent decades are likely attributable to external drivers such as large-scale anthropogenic changes in the green turtle coastal marine ecosystem. This study found that variations in sea surface temperature, salinity, and nutrient effluent discharge from nearby rivers were correlated with an increased incidence of the disease, substantiating that these may be among the significant environmental drivers impacting Fibropapillomatosis prevalence. This study offers data and insight on the need to establish a baseline of environmental factors which may drive Fibropapillomatosis and its clinical exacerbation. We highlight the multifactorial nature of this disease and support the inclusion of interdisciplinary work in future Fibropapillomatosis research efforts.