Chronic Boat Strike and Polycystic Kidneys in a Free-Ranging Florida Manatee (Trichechus manatus latirostris)
An adult, female Florida manatee (Trichechus manatus latirostris) was captured at Port of the Islands, Florida, on 18 April, 2004 as part of a manatee radio tracking study on manatee movement patterns in the Ten Thousand Islands. A full health assessment was conducted. All scar patterns were photographed, measured and recorded. Blood was collected from the brachial plexus in the pectoral flipper. A Passive Integrated Transponder (PIT) tag was surgically inserted into both the left and right shoulder regions and the animal was fitted with a satellite-linked radio telemetry transmitter; she was assigned the U.S. Geological Survey (USGS) field identification number TNP029. Based on physical evaluation and behavior at time of capture, TNP029 was assessed to be within the parameters of a healthy Florida manatee and was released into her natural habitat for monitoring under the USGS Sirenia Project.
Blood from TNP029 was evaluated at the University of Florida, College of Veterinary Medicine Clinical Pathology Laboratory within 24 hours of collection. The serum biochemistry results were diagnostic for severe inflammatory disease. This animal's movements were monitored through the USGS Sirenia Project and no behavioral or movement abnormalities were noted until the animal was reported dead on 20May2004, 32 days post capture. The carcass arrived at the Florida Fish and Wildlife Conservation Commission (FFWCC) Marine Mammal Pathology Laboratory (MMPL) in St. Petersburg, Florida within six hours of discovery. The necropsy exam, conducted immediately upon arrival, revealed a single, well healed skeg pattern scar on its dorsum, pyothorax, consolidated left lung, polycystic kidneys, colitis, multiple adhesions and fibrous tags throughout the abdominal cavity and an antemortem shark bite. Both kidneys were severely enlarged and were grossly and microscopically polycystic in appearance. Gross necropsy and histological exam findings support the conclusion that the chronic disease (pyothorax, caseous, consolidated, non-functional left lung, widespread abdominal adhesions) incurred from the blunt trauma of a boat strike was the cause of death in this manatee. Up to 33% of manatee mortality in Florida is a result of human interaction; of these watercraft strikes appear to be the most prevalent.6,16 Thoracic injury including, pyothorax, suppurative pleuritis, necrosuppurative pneumonia, rib and vertebral proliferative osteomyelitis, pneumothorax and subcutaneous emphysema are common sequela in manatees who sustain blunt trauma from watercraft.
Though well described in other species, polycystic kidneys have not been previously documented in a manatee. There are acquired, hereditary and developmental forms of the disease. Acquired or simple renal cysts may occur secondary to end stage renal failure, fibrosis or other obstructive processes. Acquired cysts are most likely the result of chronic obstruction of the tubules by interstitial fibrosis or by oxalate crystals. The manatee described in this paper showed signs most consistent with autosomal dominant adult polycystic kidney disease. However, since there were no clinical biochemical evidence that would suggest renal compromise at the time of capture one month prior to her death, we have concluded that the polycystic kidneys were an incidental finding and did not contribute to her death.
The authors would like to acknowledge the USGS and FFWCC capture crew without whom this data could not have been collected. We would also like to acknowledge the assistance of Dr. John Harvey, Ms. Melanie Pate, and the staff of the UF clinical pathology laboratory. Finally, we would like to acknowledge the staff at the Marine Mammal Pathology Laboratory who stayed late to complete this necropsy in a timely fashion. This publication was funded by Florida Fish and Wildlife Conservation Commission grant (s018) and performed under the United States Fish and Wildlife Service wildlife research permits, issued to the Sirenia Project MA791721-2 and the University of Florida permit MA067116-0.
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