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Diseases of Aquatic Organisms

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DAO 70:139-154 (2006)  -  doi:10.3354/dao070139

Neurological disease in wild loggerhead sea turtles Caretta caretta

Elliott R. Jacobson1,*, Bruce L. Homer1, Brian A. Stacy1, Ellis C. Greiner1, Nancy J. Szabo1, Cheryl L. Chrisman1, Francesco Origgi1, Sadie Coberley2, Allen M. Foley3, Jan H. Landsberg3, Leanne Flewelling3, Ruth Y. Ewing4, Richie Moretti5, Susan Schaf5, Corinne Rose5, Douglas R. Mader5, Glenn R. Harman6, Charles A. Manire7, Nancy S. Mettee8, Andrew P. Mizisin9, G. Diane Shelton9

1College of Veterinary Medicine, University of Florida, Gainesville, Florida 32610, USA
2College of Medicine, University of Florida, Gainesville, Florida 32610, USA
3Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, St. Petersburg, Florida 33701, USA
4National Marine Fisheries Service, Miami, Florida 33149, USA
5Turtle Hospital, Marathon, Florida 33050, USA
6Clearwater Marine Aquarium, 249 Windward Passage, Clearwater, Florida 33767, USA
7Mote Marine Laboratory, Sarasota, Florida 34236, USA
8Marinelife Center, Juno Beach, Florida, 33408, USA
9Department of Pathology, School of Medicine, University of California, San Diego, La Jolla, California 92093-0612, USA

ABSTRACT: 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.

KEY WORDS: Spirorchiidiasis · Brain · Spinal cord · Neuropathy · Loggerhead sea turtle · Caretta caretta

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