Abstract

An adult female, pregnant, Atlantic bottlenose dolphin (Tursiops truncatus) stranded in Vero Beach, Florida on Nov. 11, 2006. Rehabilitation efforts occurred at two different facilities in Florida, due to unsuccessful release attempts after the first rehabilitation. The animal was discovered to be deaf (confirmed by auditory evoked potential testing [AEP]) and was deemed "non-releasable" by the National Marine Fisheries Service.³

Upon arrival at the Marine Mammal Conservancy, "Castaway" showed signs of disorientation, abnormal posturing, lack of coordination, subtle intention tremors and a subtle, intermittent, unilateral, horizontal nystagmus. Despite showing neurological symptoms and signs of cognitive dysfunction on presentation, this animal made slow but consistent improvement. Most of the neurologic signs slowly resolved; however, she never regained full cognitive function (by comparison to other Tursiops in managed care) and she never regained her hearing (confirmed by follow up AEP 2 years after the first AEP).

On Jan. 18, 2010 Castaway died, after less than 24 hours of inappetance. Post mortem MRI of the brain showed one deep and one superficial lesion in the left cerebellar hemisphere and an area of increased signal intensity within the right frontal lobe.² Gross necropsy findings included a moderate to severe (180° to 240°) clockwise, mesenteric torsion, which involved rotation of the entire intestine around the root of the mesentery (presumptive mesenteric infarction). Two abscesses were present in the left hemisphere of the cerebellum, corresponding to the lesions observed on MRI. An impression smear of the abscess showed Nasitrema sp. eggs.⁴ Multi-drug resistant Morganella morganii was cultured from the cerebellar abscesses.¹ The presumptive cause of death was the mesenteric torsion.

Acknowledgements

The authors would like to thank the staff of Dolphins Plus, the staff and volunteers of the Marine Mammal Conservancy, Dr. James Bailey, Dr. Tom Schubert, Dr. Matthew Winter, Dr. Chris Torno, Dr. David Mann, Mary Wilson and the staff of the imaging department at the University of Florida, College of Veterinary Medicine and the FWC Marine Mammal Pathobiology Laboratory.

References

1.  Abdalla J, Saad M, Samnani I, Lee P, Moorman J 2006. Central nervous system infection caused by Morganella morganii. Am J Med Sci 331:44-47.

2.  Marino L, Sudheimer KD, Murphy TL, Davis KK, Pabst DA, McLellan WA, Rilling JK, Johnson JI 2001. Anatomy and three-dimensional reconstructions of the brain of a bottlenose dolphin (Tursiops truncatus) from magnetic resonance images. Anat Rec 264: 397-414.

3.  Ridgway SH, Bullock TH, Carder DA, Seeley RL, Woods D, Galambos R 1981. Auditory brainstem response in dolphins. Neurobiology 78:1943-1947.

4.  Ridgway S, Dailey M 1972. Cerebral and cerebellar involvement of trematode parasites in dolphins and their possible role in stranding. J Wildl Dis 8:33-43.