Radiographic Evaluation of a Spinal Osteoarthropathy Epizootic in Snakes Species at the San Diego Zoo
Since 2014, over 90 snakes at the San Diego Zoo have necropsy diagnoses of spinal osteoarthropathy based on histologic and radiographic evaluations. While infectious agents and associated inflammation were seen occasionally, the majority of cases were non-inflammatory, making non-infectious etiologies a consideration. A prospective clinical and radiographic evaluation of snakes on over 250 snakes was initiated. Serial assessments in a large subset of snakes showed rapidly progressive lesions often requiring euthanasia due to severe immobility.
The earliest radiographic vertebral changes are seen mid-body, on dorso-ventral (DV) radiographs, and are bilaterally symmetric. Taxonomic differences can be seen. In non-Pythonidae, square or trapezoid-shaped soft tissue densities appear on DV views cranial to the rib articulations at the level of the lateral vertebral processes. Progression involves expansion and calcification with ankyloses of vertebrae. Changes are less evident on lateral views unless severe or when proliferative changes include the dorsal aspect of the vertebral bodies. In some Pythonidae, rib flaring at the spinal articulation occurs on DV views and progresses to soft tissue and bony proliferations. As lesions progress, they are also detectable on lateral radiographic views at the rib-vertebral articulations, sometimes protruding ventrally.
The etiology of these cases is still unknown. These cases were different than most spinal lesions in the literature due to the predominantly non-inflammatory histologic changes rarely reported.1-4 In addition, these cases progressed rapidly and had consistent radiographic lesions. Having well-positioned whole-body radiographs and histology to differentiate osteomyelitis versus enigmatic non-inflammatory lesions has provided important insight into this ongoing investigation.
Thanks to the Reptile Department for their care of these snakes, the hundreds of snake hospital visits and the many hours helping with venomous snake radiographs; also to the registered veterinary technicians who spent hours taking radiographs.
1. Clancy MM, Newton AL, Sikes JM. Management of osteomyelitis caused by Salmonella enterica subsp. houtenae in a Taylor’s cantil (Agkistrodon bilineatus taylori) using amikacin delivered via osmotic pump. J Zoo Wildl Med. 2016;47:691–694.
2. Fitzgerald KT, Vera R. Spinal osteopathy. In: Mader D, ed. Reptile Medicine and Surgery. 2nd ed. St. Louis, MO: Elsevier Saunders; 2006:906–912.
3. Isaza R, Garner M, Jacobsen E. Proliferative osteoarthritis and osteoarthrosis in 15 snakes. J Zoo Wildl Med. 2000;31:20–27.
4. Ramsay EC, Daniel GB, Bern MS, Tyron W, Merryman JI, Morris PJ, Bemis DA. Osteomyelitis associated with Salmonella enterica ss arizonae in a colony of ridgenosed rattlesnakes (Crotalus willardi). J Zoo Wildl Med. 2002;33:301–310.