Chelonid Alphaherpesvirus 5 Prevalence and First Confirmed Case of Sea Turtle Fibropapillomatosis in Grenada, West Indies

SIMPLE SUMMARY: Fibropapillomatosis is a disease of sea turtles that is likely caused by the virus chelonid alphaherpesvirus-5. Sea turtles, and especially green sea turtles, can develop extensive tumors that impede foraging and swimming and can result in high morbidity and mortality. The presence of the virus has not been assessed in Grenada and fibropapillomatosis has anecdotally not been observed in the island’s sea turtle aggregates. From 2017 to 2019, a total of 167 green, leatherback, and hawksbill turtles were examined for fibropapilllomatosis. Skin and blood samples were examined for the presence of the virus and previous exposure to the virus was assessed by checking for antibodies in the blood. No signs of fibropapillomatosis or active viral infection were found in any turtle examined during the study. Antibody testing showed that 34.6% of green turtles examined had been previously exposed to the virus. In 2020, the first case of fibropapillomatosis occurred in a green turtle in Grenada and the presence of the virus was confirmed in tumor samples. These results indicate that to date, active viral infection is rare in Grenada’s turtles, although viral exposure in green sea turtles is relatively high. The impact of fibropapillomatosis in Grenada is suggested to be low at the present time, and further studies examining factors that may influence disease are warranted. ABSTRACT: Chelonid alphaherpesvirus 5 (ChHV5) is strongly associated with fibropapillomatosis, a neoplastic disease of sea turtles that can result in debilitation and mortality. The objectives of this study were to examine green (Chelonia mydas), hawksbill (Eretmochelys imbricata), and leatherback (Dermochelys coriacea) sea turtles in Grenada, West Indies, for fibropapillomatosis and to utilize ChHV5-specific PCR, degenerate herpesvirus PCR, and serology to non-invasively evaluate the prevalence of ChHV5 infection and exposure. One-hundred and sixty-seven turtles examined from 2017 to 2019 demonstrated no external fibropapilloma-like lesions and no amplification of ChHV5 DNA from whole blood or skin biopsies. An ELISA performed on serum detected ChHV5-specific IgY in 18/52 (34.6%) of green turtles tested. In 2020, an adult, female green turtle presented for necropsy from the inshore waters of Grenada with severe emaciation and cutaneous fibropapillomas. Multiple tumors tested positive for ChHV5 by qPCR, providing the first confirmed case of ChHV5-associated fibropapillomatosis in Grenada. These results indicate that active ChHV5 infection is rare, although viral exposure in green sea turtles is relatively high. The impact of fibropapillomatosis in Grenada is suggested to be low at the present time and further studies comparing host genetics and immunologic factors, as well as examination into extrinsic factors that may influence disease, are warranted.