Rheumatoid arthritis subsequent to Borrelia burgdorferi infection in two dogs.

Two dogs with clinical signs of polyarthritis developed rheumatoid arthritis subsequent to Borrelia burgdorferi infection. In both dogs, the diagnosis of B burgdorferi infection was based on clinical signs of disease and high serum B burgdorferi titer. After antibiotic administration, both dogs had decreased B burgdorferi titer, but clinical response was temporary or was lacking. The dogs subsequently were rheumatoid factor-positive (antinuclear antibody- and anti-globulin-negative) and responded to anti-inflammatory drug administration. Development of rheumatoid arthritis in both dogs after B burgdorferi infection implicates the Borrelia organism as an infective agent leading to the development of rheumatoid arthritis in dogs. Dogs with clinical signs suggestive of B burgdorferi infection should have antiglobulin, anti-nuclear antibody rheumatoid factor, and B burgdorferi tests performed to aid definitive diagnosis.