Pathology of fibropapillomatosis in Olive!Ridley turtles Lepidochelys olivacea nesting in Costa Rica

Fibropapillomatosis (FP) is a neoplastic disease that primarily affects green turtles Chelonia mydas in epidemic proportions worldwide. Although several infectious agents (herpesvirus, retrovirus, and papillomavirus) have been associated with the condition, the etiologic agent has not been isolated or characterized. Recently, FP has been reported in other sea turtle species including confirmed cases in loggerhead turtles Caretta caretta in Florida and field observations in olive ridley turtles Lepidochelys olivacea in the Pacific coasts elf Mexico and Costa Rica. Skin and tumor specimens were collected from 72 olive ridley turtles nesting in Ostional Wildlife Refuge, Costa Pica, between July and September 1997. In all, 50 tumor biopsies were examined from 25 of the affected turtles. In addition, six biopsies were examined from five turtles that did not have visible masses and served as controls. Grossly, masses were 25 mm or less in diameter, white to gray, smooth to verruciform, raised tumors of the integument of the neck and flippers. Histologically, 42 of 50 were diagnosed as fibropapillomas and eight were classified as chronic active dermatitis and not tumors. Twenty of 42 fibropapillomas were in stages of regression and 9 of the remaining 22 tumors had histological changes that suggested early degeneration within the tumor. During field surveys based cn gross lesions, prevalences of 1-10% have been reported in this nesting population. This is considered the first histopathologic confirmation of FP in olive ridley turtles.