Spinal Arthropathy Associated with Ochrobactrum anthropi in Free-ranging Cane Toads (Chaunus [Bufo] marinus) in Australia

Abstract

Inflammatory or degenerative pathology involving the vertebral bodies and/or ventral intervertebral joints has been described in numerous species, both captive and free ranging, including mammals, birds, and snakes, although never in amphibians. We described 15 cases of a newly recognized spinal arthropathy in adult cane toads ( Chaunus [Bufo] marinus), an invasive species in Australia. Grossly appreciable lesions consisted primarily of ventral proliferation of bone and cartilage that resulted in ankylosis. Histologic examination of the entire vertebral columns of the 15 affected toads revealed 13 toads to have lesions at multiple intervertebral sites, totalling 41 intervertebral joints with lesions. Most lesions involved bone and cartilage proliferation that resulted in fusion of the joint, with (n = 15) or without (n = 9) associated pyogranulomatous inflammation. In the remaining 17 affected joints, histologic lesions were characterized by degeneration of articular cartilage without joint fusion. In addition, in one of these joints, there was also hemorrhage and pyogranulomatous inflammation. Bacterial culture of affected joints in 9 toads and grossly normal joints in 4 control toads resulted in isolation of Ochrobactrum anthropi in 7 affected toads but in none of the controls ( P < .01). We proposed an interaction between degenerative and bacterial etiologies in the pathogenesis of this condition. Invasive toads may be predisposed to this condition because of their large size; increased rates of movement; and, possibly, immunosuppression resulting from inhabiting a novel environment.