Abstract

A 19-year-old male bottlenose dolphin (Tursiops truncatus) presented with inappetence and mild anemia. Ultrasound revealed a large volume pleural effusion filling the left hemithorax. Coagulation testing, fungal, viral, and bacterial PCRs, fecal analysis, and sputum cytology and culture were unremarkable. Initial fluid examination was suggestive of hemothorax; however, follow-up cytological evaluations were consistent with chronic non-chylous lymphatic effusion with mild chronic hemorrhage. Computed tomography (CT) additionally revealed two ipsilateral rib fractures, nodular pleuritis, marginal lymphadenopathy, left-sided atelectasis, and suspected dilation of the thoracic duct and internal thoracic veins. An indwelling chest drain was impractical for an aquatic habitat; thus, a series of therapeutic pleural drainage procedures were performed. Repeat CT demonstrated marked reduction in pleural effusion with persistence of thoracic duct dilation and mass-like areas of pleural thickening. Over 24 months, 21.48 L was removed. Serial ultrasound examinations identified resolution of the effusion 14 months after presentation, however, recrudescence occurred 5 months later. Lipid extracts from pleural fluid and serum were analyzed using a non-targeted lipidomics method. Fifteen lipids were significantly higher in the serum compared with controls (n=3), and included ceramides, lysophospholipids, and ether-phospholipids, which have been implicated with inflammation, cell death, or neoplasia. Humane euthanasia was ultimately elected following patient clinical decline. Necropsy confirmed chronic severe pleural fibrosis with chronic hemorrhage, severe pleural effusion, and mediastinal fibrosis with entrapped lymph nodes and thymic tissue. These are possible sequelae to pleurisy secondary to previous rib fractures. While rib fractures are common findings in wild dolphins at necropsy,^1,2 this is the first report of chronic non-chylous lymphatic pleural effusion in a bottlenose dolphin.

Acknowledgements

The authors wish to thank University of Florida Aquatic Animal Health Program for providing funding of lipidomic analysis, Dr. Hendrik Nollens of the Pacific Marine Mammal Center, Dr. Judy St. Leger of St. Leger Consulting, Dr. Douglas Owens of BluePearl Specialty and Emergency Hospital, SSgt. Jeremy Guancia, TSgt. Jennifer Thompson, MSgt. Nicola Paille and the entire radiology department at the U.S. Air Force Medical Service at Wilford Hall Ambulatory Surgical Center, as well as the hospital and animal care staff at SeaWorld San Antonio. This is a SeaWorld contribution.

*Presenting author

Literature Cited

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