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

Fibropapillomatosis (FP) is a neoplastic disease that primarily affects gre en turtles Chelonia mydas in epidemic proportions worldwide. Although sever al infectious agents (herpesvirus, retrovirus, and papillomavirus) have bee n associated with the condition, the etiologic agent has not been isolated or characterized. Recently, FP has been reported in other sea turtle specie s including confirmed cases in loggerhead turtles Caretta caretta in Florid a and field observations in olive ridley turtles Lepidochelys olivacea in t he 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 wer e 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 c ontrols. Grossly, masses were 25 mm or less in diameter, white to gray, smo oth to verruciform, raised tumors of the integument of the neck and flipper s. Histologically, 42 of 50 were diagnosed as fibropapillomas and eight wer e classified as chronic active dermatitis and not tumors. Twenty of 42 fibr opapillomas were in stages of regression and 9 of the remaining 22 tumors h ad histological changes that suggested early degeneration within the tumor. During field surveys based cn gross lesions, prevalences of 1-10% have bee n reported in this nesting population. This is considered the first histopa thologic confirmation of FP in olive ridley turtles.