Nonsuppurative polyarthritis is an infectious condition of older, growing lambs (6 wk to 4 mo old) characterized by high morbidity and moderate to severe lameness with enlargement of affected joints.
The infectious agent, Erysipelothrix rhusiopathiae, is thought to infect the animal through wounds created as a result of tail docking and castration procedures. However, outbreaks may also occur after “bloodless” procedures, particularly during extended periods of wet weather, which increases the level of stress and appears to enhance the survivability of the organism in the environment. E rhusiopathiae localizes in joints via hematogenous dissemination and infects the synovial membrane. Progression of the synovial infection results in synovitis and damage to articular cartilage and underlying subchondral bone.
Clinical Findings and Lesions
Sudden onset of moderate to severe lameness in a high number of growing lambs is suggestive of nonsuppurative polyarthritis. Lameness typically occurs in 2 or more limbs, and the joints most often affected are the carpus and hock. Affected lambs are reluctant to move and spend extended periods of time in sternal recumbency. Growth is often severely depressed. Progression of the condition results in proliferation of the synovial membrane, thickening of the joint capsule without significant joint effusion, and eventual erosion of articular cartilage.
Sudden onset of lameness in a large number of growing-age lambs is suggestive of polyarthritis due to E rhusiopathiae. Because joint effusions are minimal, attempts to obtain a sample from affected joints for culture and other diagnostics may be unsuccessful.
Prevention and Treatment
Vaccination should be considered on premises where the disease is a recurring problem. Adopting strict antiseptic techniques and maintaining hygienic conditions for tail docking and castration are recommended but may not prevent the condition. The so-called “bloodless” methods of performing both procedures may reduce the chances of wound contamination, but outbreaks are still possible. Administration of penicillin for 5 days is recommended for effective treatment of the nonsuppurative polyarthritis. Administration of NSAID aids in improving lameness.
Last full review/revision March 2012 by Darryl Ragland, DVM, PhD