Nonsuppurative polyarthritis is an infectious condition of older, growing lambs (6–16 weeks old) characterized by high morbidity and moderate to severe lameness with enlargement of affected joints.
Etiology of Nonsuppurative Polyarthritis in Lambs
The infectious agent of nonsuppurative polyarthritis, 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 of Nonsuppurative Polyarthritis in Lambs
Sudden onset of moderate to severe lameness in a high number of growing lambs is suggestive of nonsuppurative polyarthritis. Lameness typically occurs in two 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. Some lambs may eventually develop chronic polyarthritis. 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.
Diagnosis of Nonsuppurative Polyarthritis in Lambs
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 of Nonsuppurative Polyarthritis in Lambs
Vaccination is recommended where the disease is a recurring problem
Recommended treatment is penicillin for 5 days
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 NSAIDs helps improve lameness.
Older, growing lambs may suddenly develop moderate to severe lameness associated with E rhusiopathiae infection, known as nonsuppurative polyarthritis.
Postdipping lameness is a form of E rhusiopathiae infection previously described in lambs and adult sheep associated with antiparasitic "dip" treatments given after shearing or mulesing. This form of infection, in which the bacterium penetrated via skin abrasions, has become less frequent as a result of the reduced use of sheep dips.