Corneal Fibropapilloma in Loggerhead Turtles (Caretta caretta) in Mediterranean Sea

Fibropapillomatosis (FP) is a panzootic and neoplastic disease. In the current study, we aimed to characterize a tumour-like mass and reveal spirorchid-like parasitic eggs in the ocular tissues of Caretta caretta turtles. In this study, seven ocular tissue samples, including six eye/eyelid tissues taken from Loggerhead turtles (C. caretta) with healthy-looking animals and one tumour-like ocular mass obtained from a C. caretta turtle with a clinical lesion, were used as study material. Unilateral spirorchid-like parasite eggs were detected in the tissue samples of only two healthy-looking animals. The characterization and identification of a tumour-like mass were performed using histopathology, PCR and immunohistochemistry, respectively. Unilateral corneal scarring, spirorchid-like parasite eggs and papilloma virus by PCR were detected in the ocular tumour-like mass evaluated as fibropapilloma. However, in immunohistochemical staining, Ki-67, p16, pan-cytokeratin, vimentin and herpesvirus showed positive staining, whereas p53 showed negative staining. Koilocytosis was observed in some cells. Our findings indicate that papillomavirus, herpesvirus and spirorchid-like parasite eggs may have a predisposing role in the occurrence of FP. This study provides the first research data on spirorchid-like parasite eggs and FP in loggerhead turtles (C. caretta) in the Mediterranean Sea in Türkiye.