Abstract

A retrospective study on polyarthritis in Maxwell’s duikers (Cephalophus maxwellii) was conducted at the Bronx Zoo from 1982–2003. Medical records from a total of 96 Maxwell’s duikers were reviewed. Forty-eight of those animals reached at least one year of age and remained at the Bronx Zoo (i.e., not transferred to another institution). Of the 48 animals, 13 animals, (four males and nine females) between the ages of two and seven years, presented with polyarthritis.

The polyarthritis manifest in the carpi and tarsi. No other joints were affected. Clinically, animals presented with carpal and/or tarsal swelling with minimal lameness until late in the disease process. In severe cases, luxations of the carpi developed that could not be stabilized with external coaptation. Radiographically, the disease was characterized by soft tissue swelling, joint space narrowing, erosion of articular surfaces, and new bone formation (periosteal reaction) along the joint margins. There were no differences in complete blood counts, serum biochemical analyses, mineral panels, and serology (including tests for lentiviruses, Borrelia burgdorferi, and rheumatoid factor) between affected and non-affected animals. In most cases, arthrocentesis was performed for joint cytology and microbiologic culture with sensitivity. Mycoplasma sp. was cultured from one animal. Treatments included antibiotics, analgesics, and, in some cases, steroid therapy. No treatment proved successful. One affected animal currently remains in the collection, and all previous cases were humanely euthanatized due to the severity of the disease.

The cause of the polyarthritis in these cases remains undetermined. Results of radiographic examinations are consistent with immune-mediated polyarthritis/rheumatoid arthritis; however, this has not been verified by laboratory investigations.