From December, 1997, through November, 2000, 306 deaths were documented among adult and subadult American alligators (Alligator mississippiensis) of Lake Griffin, Florida (USA). Some live alligators were lethargic and unresponsive to approach. To determine the cause, we examined ten alligators captured from Lake Griffin between December 1997 and June 1999. Initially, four alligators, three of which were clinically unresponsive, were sacrificed for routine diagnostic necropsy. The other six Lake Griffin alligators, and five control alligators captured from Lake Woodruff National Wildlife Refuge, Florida, where mortality was negligible, were studied extensively by clinical neurologic examination, electromyography, hematology, serum chemical analyses, and blood culture, then sacrificed and necropsied. Samples of brain, spinal cord, peripheral nerves, skeletal muscle, and major internal organs were examined by light microscopy for abnormalities. Samples of nervous tissue also were examined by electron microscopy, and samples of various tissues were collected for toxicologic analyses. Clinical signs included swimming in circles, inability to submerge, lethargy, weakness, unresponsiveness, slow reflexes, dragging the dorsal surfaces of the hind feet, head tilt, and anisocoria. Lake Griffin alligators had significantly lower distal sciatic nerve conduction velocities than Lake Woodruff alligators, and the most severely affected alligators had the lowest velocities; but morphologic abnormalities in peripheral nerves were not evident in most cases. Three severely affected alligators had acute focal necrosis of the torus semicircularis in the midbrain, two had skeletal myofiber atrophy, another had diffuse nonsuppurative encephalomyelitis, and one mildly affected alligator had skeletal myodegeneration. The cause or causes have not yet been identified.
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April 01 2002
CLINICAL AND NECROPSY FINDINGS ASSOCIATED WITH INCREASED MORTALITY AMONG AMERICAN ALLIGATORS OF LAKE GRIFFIN, FLORIDA
Trenton R. Schoeb;
Trenton R. Schoeb
7
1 Division of Comparative Medicine, Department of Pathobiology, University of Florida College of Veterinary Medicine, Gainesville, Florida 32611, USA
6 Current address: Department of Genomics and Pathobiology, University of Alabama at Birmingham, 402 Volker Hall, 1670 University Blvd, Birmingham, Alabama 35294-0019, USA
7 Corresponding author (e-mail: trs@uab.edu)
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Terrell G. Heaton-Jones;
Terrell G. Heaton-Jones
1 Division of Comparative Medicine, Department of Pathobiology, University of Florida College of Veterinary Medicine, Gainesville, Florida 32611, USA
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Roger M. Clemmons;
Roger M. Clemmons
2 Department of Small Animal Clinical Sciences, University of Florida College of Veterinary Medicine, Gainesville, Florida 32611, USA
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Dwayne A. Carbonneau;
Dwayne A. Carbonneau
3 Florida Fish and Wildlife Conservation Commission, 4005 S. Main St., Gainesville, Florida 32601, USA
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Allan R. Woodward;
Allan R. Woodward
3 Florida Fish and Wildlife Conservation Commission, 4005 S. Main St., Gainesville, Florida 32601, USA
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Diane Shelton;
Diane Shelton
4 Comparative Neuromuscular Laboratory, University of California San Diego, La Jolla, California 92093, USA
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Robert H. Poppenga
Robert H. Poppenga
5 Laboratory of Pathology and Toxicology, New Bolton Center, University of Pennsylvania, Kennett Square, Pennsylvania 19348, USA
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J Wildl Dis (2002) 38 (2): 320–337.
Article history
Received:
December 27 2000
Citation
Trenton R. Schoeb, Terrell G. Heaton-Jones, Roger M. Clemmons, Dwayne A. Carbonneau, Allan R. Woodward, Diane Shelton, Robert H. Poppenga; CLINICAL AND NECROPSY FINDINGS ASSOCIATED WITH INCREASED MORTALITY AMONG AMERICAN ALLIGATORS OF LAKE GRIFFIN, FLORIDA. J Wildl Dis 1 April 2002; 38 (2): 320–337. doi: https://doi.org/10.7589/0090-3558-38.2.320
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