Nocardia arthritidis infection in the distal metaphysis of the metatarsal III and IV bone of a heifer.

Case Description: A 19-month-old 536.4-kg (1,180-lb) Brown Swiss heifer was referred for evaluation of a firm swelling over the distal aspect of the right metatarsal region and chronic lameness in the right hind limb.

Clinical Findings: Examination of radiographs of the right metatarsophalangeal joints revealed an expansile, smoothly marginated, cyst-like lesion within the distal metaphysis of the metatarsal III and IV bone. Differential diagnoses included bone abscess, bone cyst, aneurysmal bone cyst, neoplasia, osteomyelitis, and metabolic bone disease. Aerobic microbial culture of the aspirate yielded moderate growth of branching, gram-positive, rod-shaped bacteria, which were presumptively identified as Nocardia spp. The isolate was subsequently identified as Nocardia arthritidis by 16S rRNA gene sequence analysis.

Treatment And Outcome: The lesion was surgically debrided, lavaged, and bandaged. Exercise was restricted, and systemic and local administration of antimicrobials was instituted. After a communication between the abscess and the metatarsophalangeal joints was iatrogenically created, the extralabel use of aminoglycosides was initiated. The heifer had noticeable clinical improvement within 2 weeks after initial evaluation and reportedly had no evidence of lameness and minimal external blemishes 3 months after the second evaluation.

Clinical Relevance: To our knowledge, this is the first report on the diagnosis and management of a long-bone abscess attributable to N arthritidis infection in cattle. Complications encountered during treatment and the decision to engage in extralabel use of antimicrobial agents in the heifer described here may serve as a guide for food animal practitioners faced with the treatment of valuable cattle.