Progressive Lameness of a Greater One-Horned Rhinoceros (Rhinoceros unicornis) Associated with a Retroperitoneal Abscess and Thrombus Caused by Streptococcus dysgalactiae Subspecies equisimilis

SIMPLE SUMMARY: Movement disorders can have different origins and certain causes require a particular intervention management. In rhinoceroses, lesions affecting the extremities per se are typical causes. A 3-year-old, male Greater one-horned rhinoceros born in captivity developed progressive lameness, ataxia with dragging of its right, hind hoof. Prior, the animal was housed together with his dam, which was repeatedly aggressive against her offspring. Despite therapy, the symptoms aggravated and the animal died spontaneously. At necropsy, a large abscess in the abdomen under the spine and a thrombus of the artery of the right hind limb were diagnosed as the cause of lameness. The pyogenic bacterium Streptococcus dysgalactiae subspecies equisimilis was isolated from the abscess and from mucous membranes of the healthy mother. Such an unusual origin for lameness should be considered in rhinoceroses in the future. ABSTRACT: In rhinoceroses, lameness is an occasionally seen symptom primarily caused by lesions affecting the feet and interdigital space. A 3-year-old male Greater one-horned rhinoceros developed a progressive, severe movement disorder of the right hind limb with subsequent death. The pathological analysis diagnosed a severe, retroperitoneal abscess and chronic thrombosis of the right iliac artery. Streptococci detected in the abscess were further identified as Streptococcus dysgalactiae subspecies equisimilis by culture and molecular techniques. The identical isolate was also identified in a vaginal swab of the dam. The list of differential diagnoses for lameness in rhinoceroses must be expanded by processes affecting other than the extremities per se.