Recognizing the Most Common Clinical Signs of Lyme Disease in Dogs

Lyme disease, or canine borreliosis, stands as one of the most clinically relevant and geographically widespread vector-borne illnesses affecting dogs globally. Caused by the spirochete bacterium Borrelia burgdorferi and transmitted primarily by the bite of the blacklegged tick (Ixodes scapularis), this condition often presents a diagnostic paradox. While massive public awareness exists regarding tick control, the clinical signs of established infection in dogs can be subtle, non-specific, or even absent for months, making early detection a significant challenge for both pet owners and veterinary professionals.

A professional understanding of the most common presenting signs is crucial, as delayed diagnosis not only prolongs discomfort but significantly increases the risk of severe, often fatal, systemic complications.

1. The Causative Mechanism and Latency Period

Lyme disease transmission requires the infected tick to attach and feed for a sustained period, typically 24 to 48 hours, allowing the B. burgdorferi spirochetes to migrate from the tick's gut into the host’s bloodstream.

Crucially, the infection, once established, does not always translate immediately into visible disease. The incubation period following exposure is highly variable, ranging from two to five months before clinical signs fully manifest. This latency means that owners may not connect the onset of symptoms with a tick bite that occurred half a year prior, often complicating the initial history-taking process.

In the majority of infected dogs (estimated at over 80%), the infection remains subclinical, meaning the dog tests positive for antibodies but shows no outward signs of illness. For the remaining population, the disease typically targets the joints, kidneys, and, less frequently, the cardiac or neurological systems.

2. The Cardinal Sign: Recurrent and Shifting Lameness

The hallmark clinical presentation of canine Lyme disease revolves around musculoskeletal inflammation. This is commonly referred to in clinical settings as Lyme arthritis or polyarthritis.

A. Shifting Leg Lameness (Polyarthritis)

This is arguably the single most common and defining sign observed in symptomatic dogs. The lameness is characteristically recurrent, sudden, and often transitory (shifting). In practice, this means:

1. Sudden Onset: A dog may wake up severely lame on one limb (often a front leg) seemingly without trauma.
2. Shifting Localization: After a few days, the lameness may resolve completely, only to reappear minutes, hours, or days later in a different limb. The inflammation (synovitis) is not permanently fixed to one joint; rather, it shifts as the bacteria localize and trigger an immune response in various synovial membranes throughout the body.
3. Pain and Heat: Affected joints, often the hocks, elbows, or carpi, may be visibly swollen (joint effusion), warm to the touch, and intensely painful upon palpation, leading to reluctance to move or a stiff gait.

The recurrent nature of the lameness can lead owners to attribute the discomfort to minor injury or aging, delaying veterinary consultation. However, polyarthritic pain associated with Lyme disease is often acute and significantly debilitating during flare-ups.

B. Generalized Stiffness and Reluctance to Move

Beyond acute lameness, dogs suffering from Lyme arthritis often exhibit a generalized stiffness, particularly after resting or upon waking. They may show a decreased willingness to engage in normal activities—reluctance to jump onto furniture, lag behind on walks, or demonstrate difficulty climbing stairs. This general malaise is a direct result of ongoing systemic inflammation and joint pain.

3. Systemic and Non-Specific Manifestations

While locomotor issues are the clearest indicators of Lyme infection, the body's generalized reaction to the spirochete often produces non-specific signs that mimic other infectious or inflammatory conditions. These signs reflect the acute phase of the systemic infection.

A. Pyrexia (Fever)

In acute cases, especially those involving polyarthritis, a moderate to high fever (typically ranging from 103°F to 105°F) is common. The fever may fluctuate, corresponding with the recurrence of joint inflammation.

B. Lethargy and Malaise

Systemic inflammation and the energy expenditure involved in fighting the infection lead to profound lethargy. The dog appears tired, depressed, and significantly lacks energy. This symptom is often the first thing owners notice, even before the lameness becomes obvious.

C. Anorexia and Weight Loss

Due to fever and general discomfort, dogs may experience temporary or prolonged decreased appetite (anorexia). If the disease remains untreated, the chronic inflammatory state and pain can lead to significant weight loss.

D. Lymphadenopathy

Swelling of the regional lymph nodes (lymphadenopathy), particularly those draining the site of the infection (often the prescapular or popliteal nodes), is frequently noted upon physical examination as the body ramps up its immune response.

4. The Critical Complication: Lyme Nephritis

Although joint issues are the most common presentation, the most severe and life-threatening complication of Lyme disease is the development of Lyme-associated nephropathy, often termed protein-losing nephropathy (PLN) or glomerulonephritis. This condition arises from the sustained deposition of immune complexes in the kidney filtration units (glomeruli), which progressively damages the organ structure.

Lyme nephritis is relatively rare, but when it occurs, the prognosis is often grave and requires immediate, aggressive intervention. Certain breeds, including Labrador Retrievers, Golden Retrievers, Shetland Sheepdogs, and Bernese Mountain Dogs, appear to have a genetic predisposition to this severe immune-mediated complication.

Signs indicative of progressive renal failure include:

• Proteinuria: Excessive protein loss in the urine, detectable only through laboratory testing.
• Polydipsia/Polyuria (PUPD): Increased thirst and increased urination, classic signs of kidney damage.
• Edema: Swelling, particularly in the limbs or abdomen (ascites), due to low protein levels in the blood (hypoalbuminemia).
• Azotemia: Elevated kidney waste products (BUN and creatinine) in the blood, indicating significant decline in renal function.
• Vomiting and Severe Lethargy: Reflecting the toxic effects of uremia (accumulation of waste products).

While joint disease is treatable and usually carries a favorable prognosis, the development of Lyme nephritis necessitates prompt diagnostic confirmation and often requires complex management to slow the progression of fatal kidney failure.

Conclusion: Vigilance and Proactive Care

The clinical signs of canine Lyme disease are diverse, ranging from subtle lethargy to life-threatening kidney dysfunction. Given the high rate of subclinical infection and the potential for severe complications, professional vigilance is essential. Owners should maintain meticulous tick control protocols throughout the year, especially in endemic areas, and regularly inspect their pets.

If a dog presents with recurrent lameness, fever, or any significant change in thirst/urination, diagnostic testing (including the C6 antibody test) is warranted. Early diagnosis and the administration of appropriate antibiotic therapy, typically doxycycline, usually lead to rapid resolution of the acute symptoms, highlighting why prompt recognition of these common signs remains the best defense against the silent burden of canine borreliosis.