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In this VetGirl podcast, we discuss clinical signs seen with Lyme disease. Lyme disease is caused by the spirochete Borrelia burgdorferi (Bb). In dogs, three states of Lyme disease can be seen. With acute Lyme disease, dogs typically develop transient fever, lethargy, depression, hesitance to move, anorexia, pain, lymphadenopathy, and acute arthritis (seen as a mono- or polyarthropathy). Joints may be inflamed and warm to the touch. Sub-acute signs may also be seen, where lameness can last several weeks. While clinical arthritis may be transient, inflammatory changes to the synovial fluid may be ongoing and potentially persistent. Typically, lameness in dogs occurs months after tick exposure. Chronic signs include cardiac changes (e.g., bradyarrhythmias such as heart block, etc.), neurologic signs, arthritis and changes related to Lyme nephritis (estimated to occur in 1-2% of dogs affected by Lyme disease).
Lyme nephritis is a rare but fatal complication seen with Bb. Lyme nephritis is not caused by an inflammatory response to renal invasion of Bb organisms, but rather thought to be a condition due to accumulation of immune complexes in the kidney. Unique histopathologic changes to the kidneys have been identified with Lyme nephritis and include immune-mediated glomerulonephritis, lymphocytic-plasmacytic interstitial nephritis, and diffuse tubular necrosis and regeneration. Chronic signs of Lyme nephritis include inappetance, vomiting, muscle wasting, weight loss, lethargy, and malaise, and can progress to halitosis, azotemia, edema, and death. Certain breeds including golden retrievers and Labrador retrievers seem to be over-represented. Even with aggressive treatment, long-term prognosis is guarded to grave, with one study showing that 49/49 dogs diagnosed with Lyme nephritis were all euthanized within 1-8 weeks of diagnosis.
References available upon request.