Cervical Vertebral Instability in Komodo Dragons (Varanus komodoensis)
American Association of Zoo Veterinarians Conference 2007
Dawn M. Zimmerman1, DVM, MS; Michael Douglass1, DVM; Meg Sutherland-Smith2, DVM, DACZM; Roberto Aguilar3, DVM; Willem Schaftenaar4, DVM; Andy Shores5, DVM, MS, PhD, DACVIM (Neurology)
1Memphis Zoo and Aquarium, Memphis, TN, USA; 2San Diego Zoo, San Diego, CA, USA; 3Phoenix Zoo, Phoenix, AZ, USA; 4Rotterdam Zoo, Rotterdam, The Netherlands; 5Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS, USA
Abstract
Cervical instability with secondary neurologic disease appears to be emerging as a significant cause of morbidity and mortality in captive Komodo dragons (Varanus komodoensis). Four confirmed cases of cervical subluxation resulting in nerve root and/or spinal cord compression are identified. In addition, four similar cases are acknowledged although the cause of neurologic signs is unconfirmed. All were adults (age range 10.5–17.5 yr) with no sex predilection apparent. Of the confirmed cases, three were trauma-induced and one had an unknown inciting cause. Cervical vertebrae affected included C1–C4. Clinical signs on presentation included ataxia, ambulatory paraparesis or tetraparesis to tetraplegia,1 depression to unresponsiveness, cervical scoliosis, and anorexia (primarily caused by inability to hyperextend neck as part of normal feeding strategy). Diagnosis of compression was confirmed with magnetic resonance imaging or computed tomography. Treatment ranged from supportive care to attempted surgical decompression. All cases resulted in mortality, ranging in time from 4 days to 14 mo post-presentation. Timely surgical intervention may be paramount for recovery. Necropsy findings primarily included axonal demyelinization, Wallerian degeneration, and cell necrosis of the spinal cord. Possible pathologies to investigate include cervical malformation resulting in ligament laxity and subsequent subluxation (similar to wobbler syndrome in dogs) and the presence of axonal demyelinization with Wallerian degeneration. Predilection for cervical subluxations may correlate with genetics of the species as well as captive dietary regimens. Care should be exercised with procedures involving manual restraint of Komodo dragons at the neck or manipulation of the neck.
Literature Cited
1. Aguilar, R.F., E. Hammond, M. Mitchell, C. Arcement, M. Garner, and A. Delahunta. 2005. Acute tetraparesis associated to cervical vertebral instability in an adult male komodo dragon (Varanus komodoensis). Proc. Am. Assoc. Zoo Vet. Pp. 106–110.