RESUMEN
Chelonid alphaherpesviruses 5 and 6 (ChHV5 and ChHV6) are viruses that affect wild sea turtle populations. ChHV5 is associated with the neoplastic disease fibropapillomatosis (FP), which affects green turtles (Chelonia mydas) in panzootic proportions. ChHV6 infection is associated with lung-eye-trachea disease (LETD), which has only been observed in maricultured sea turtles, although antibodies to ChHV6 have been detected in free-ranging turtles. To better understand herpesvirus prevalence and host immunity in various green turtle foraging aggregations in Florida, USA, our objectives were to compare measures of innate and adaptive immune function in relation to (1) FP tumor presence and severity, and (2) ChHV5 and ChHV6 infection status. Free-ranging, juvenile green turtles (N = 45) were captured and examined for external FP tumors in Florida's Big Bend, Indian River Lagoon, and Lake Worth Lagoon. Blood samples were collected upon capture and analyzed for ChHV5 and ChHV6 DNA, antibodies to ChHV5 and ChHV6, in vitro lymphocyte proliferation using a T-cell mitogen (concanavalin A), and natural killer cell activity. Despite an overall high FP prevalence (56%), ChHV5 DNA was only observed in one individual, whereas 20% of turtles tested positive for antibodies to ChHV5. ChHV6 DNA was not observed in any animals and only one turtle tested positive for ChHV6 antibodies. T-cell proliferation was not significantly related to FP presence, tumor burden, or ChHV5 seroprevalence; however, lymphocyte proliferation in response to concanavalin A was decreased in turtles with severe FP (N = 3). Lastly, green turtles with FP (N = 9) had significantly lower natural killer cell activity compared to FP-free turtles (N = 5). These results increase our understanding of immune system effects related to FP and provide evidence that immunosuppression occurs after the onset of FP disease.
RESUMEN
Ozobranchus margoi and Ozobranchus branchiatus are the only two species of marine turtle leeches (Ozobranchus spp.) known to inhabit the Atlantic coast of the United States and the Gulf of Mexico. In early reports of fibropapillomatosis (FP) in green turtles (Chelonia mydas), O. branchiatus was implicated as a vector in the transmission of Fibropapilloma-associated turtle herpesvirus (FPTHV). It is imperative that the leech species be identified to elucidate the role Ozobranchus spp. may play in disease transmission. In this study, Ozobranchus branchiatus has been identified for the first time on a loggerhead (Caretta caretta) turtle, and the molecular data for this species is now available for the first time in GenBank. Both species of leeches were also found infecting a single C. mydas. Using morphological taxonomy combined with distance- and character-based genetic sequence analyses, this study has established a DNA barcode for both species of Ozobranchus spp. leech and has shown it can be applied successfully to the identification of leeches at earlier stages of development when morphological taxonomy cannot be employed. The results suggest a different haplotype may exist for O. branchiatus leeches found on C. caretta versus C. mydas. Leech cocoon residue collected from a C. mydas was identified using the new method.