Clinical and necropsy findings associated with increased mortality among American alligators of Lake Griffin, Florida

Trenton R. Schoeb, Terrell G. Heaton-Jones, Roger M. Clemmons, Dwayne A. Carbonneau, Allan R. Woodward, Diane Shelton, Robert H Poppenga

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


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 semi-circularis 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.

Original languageEnglish (US)
Pages (from-to)320-337
Number of pages18
JournalJournal of Wildlife Diseases
Issue number2
StatePublished - Apr 2002
Externally publishedYes


  • Alligator mississippiensis
  • American alligator
  • Electromyography
  • Encephalopathy
  • Florida
  • Neuropathy

ASJC Scopus subject areas

  • veterinary(all)


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