Pharmacokinetics of ponazuril after administration of a single oral dose to green turtles (Chelonia mydas).

The coccidian protozoan, Caryospora cheloniae, has been associated with severe enteritis and encephalitis in immature farm-raised green turtles (Chelonia mydas) in the Cayman Islands, immature green turtles off the coast of Florida, and immature stranded sea turtles in Australia. An effective anti-coccidial drug that is both orally absorbed and well-distributed throughout the body is needed for treatment of turtles diagnosed with coccidiosis in rehabilitation facilities. Ponazuril is a triazine antiprotozoal drug that is approved in the USA for the treatment of another Apicomplexan, Sarcocystis neurona, and has also been successfully used in the therapy of other coccidian parasites. The objective of this study was to perform an oral dose-ranging pilot study (10-100 mg/kg of body weight ponazuril) in green turtles (N = 9), followed by oral administration of ponazuril at 100 mg/kg body weight (N = 8) to assess its disposition. Another goal of this study was to optimize the method of oral drug administration to green turtles. Plasma ponazuril concentrations were quantified using high performance liquid chromatography (HPLC). Standard compartmental models were fit to the data. Ponazuril was absorbed after oral administration at 100 mg/kg BW, with a maximum plasma concentration of 3.3 µg/ml. Dose-dependent pharmacokinetic parameters only weakly correlated with the dose rate, apparently due to considerable pharmacokinetic variability observed between turtles. Administration of ponazuril in gelatin capsules using a balling gun was deemed the least variable and most successful method of drug administration. Further studies are needed to evaluate the safety and efficacy of ponazuril in sea turtles with coccidiosis.

Neurological disease in wild loggerhead sea turtles Caretta caretta.

Beginning in October 2000, subadult loggerhead sea turtles Caretta caretta showing clinical signs of a neurological disorder were found in waters off south Florida, USA. Histopathology indicated generalized and neurologic spirorchiidiasis. In loggerhead sea turtles (LST) with neurospirorchiidiasis, adult trematodes were found in the meninges of the brain and spinal cord of 7 and 3 affected turtles respectively, and multiple encephalic intravascular or perivascular eggs were associated with granulomatous or mixed leukocytic inflammation, vasculitis, edema, axonal degeneration and occasional necrosis. Adult spirorchiids were dissected from meningeal vessels of 2 of 11 LST brains and 1 of 10 spinal cords and were identified as Neospirorchis sp. Affected LST were evaluated for brevetoxins, ciguatoxins, saxitoxins, domoic acid and palytoxin. While tissues from 7 of 20 LST tested positive for brevetoxins, the levels were not considered to be in a range causing acute toxicosis. No known natural (algal blooms) or anthropogenic (pollutant spills) stressors co-occurred with the turtle mortality. While heavy metal toxicosis and organophosphate toxicosis were also investigated as possible causes, there was no evidence for their involvement. We speculate that the clinical signs and pathologic changes seen in the affected LST resulted from combined heavy spirorchiid parasitism and possible chronic exposure to a novel toxin present in the diet of LST.

Distribution of chelonid fibropapillomatosis-associated herpesvirus variants in Florida: molecular genetic evidence for infection of turtles following recruitment to neritic developmental habitats.

Marine turtle fibropapillomatosis is associated with chelonid fibropapilloma-associated herpesvirus (C-FP-HV) and commonly affects juvenile green turtles (Chelonia mydas) in neritic (nearshore) habitats. Green turtles have a complex life history, characterized by shifts in trophic level as well as habitat during ontogeny. Thus, several hypotheses can be proposed for when turtles become infected with C-FP-HV. They may acquire the virus at an early stage in the life cycle, including prenatal, hatchling, or the posthatchling pelagic stages. Alternatively, they may become infected later in life after they emigrate from the open ocean to neritic habitats. Each hypothesis generates predictions about the spatial distribution of genetic variants of C-FP-HV among nearshore sites within a region. Sequencing of polymerase chain reaction-amplified viral DNA from fibropapillomas of individual turtles was used to genotype the viral variants present in marine turtles from different coastal areas in Florida. We found four distinct virus variants (A, B, C, and D), two of which (A and C) were present in multiple turtle species. Green turtles in Florida were infected with variants A, B, and C. Variant A was found in green turtles from all three areas. Outside the Indian River Lagoon, variant A was most commonly detected and was found in >94% of diseased green turtles and 70% of loggerhead sea turtles (Caretta caretta) in the Florida Bay/Florida Keys. However, in the Indian River Lagoon, variant B was found in >94% of affected green turtles. Variant B was not detected outside of the Indian River system. Chi-square analysis strongly supported (P<0.001) an association between viral variant distribution in green turtles and location. On the basis of the assumption that juvenile green turtles found in Florida's west-central coast, Florida Keys, and Indian River Lagoon areas represented recruits from a mixed pelagic population, we expected that the distribution of viral variants in these turtles would be relatively homogeneous among locations; this would correspond to infection in the earlier phases of their life cycle. The heterogeneous distribution of viral variants in green turtle tumors from different Florida coastal locations strongly supports the hypothesis that, during epizootics, turtles are infected with specific C-FP-HV variants after they arrive as juveniles in neritic habitats. The conclusion that C-FP-HV is acquired after turtles recruit to nearshore habitats should help focus further research efforts on understanding the mechanisms of transmission and raises the possibility that the effect of fibropapillomatosis on turtle populations might be reduced by management strategies designed to break the cycle of transmission in these locations.