Clinical Signs & Symptoms

Subclinical infection is common in dogs. When chronic infection does develop in individual dogs, it may persist for several years. In addition, re-infection or co-infections with other tick-transmitted organisms may occur. When clinical disease occurs, the most common signs are:
Lethargy (weakness / loss of energy)
Anorexia (loss of appetite leading to weight loss)
Pyrexia (fever)
Inflammatory arthritis – maybe mono- or polyarthritis (single or multiple joint involvement)
Lymphadenopathy (swollen / enlarged lymph nodes)

In rare cases, renal (kidney), cardiac (heart), and neurologic forms of the disease can develop. Renal Borreliosis (also known as Lyme nephritis) is generally fatal. It is characterised by severe kidney problems, and abnormalities can include uremia, hyperphospataemia, and severe protein-losing nephropathy, often accompanied by peripheral oedema. In the cardiac form, conduction abnormalities with bradycardia (slow heart rate) can occur. In the neurologic form, paralysis and seizure disorders have been reported.

There is little information available regarding incubation periods for naturally infected dogs. However, joint disease following experimentally-induced infection presents after two to five months. The first episode of arthritis is generally in the limb closest to the tick bite. In untreated or inadequately treated dogs, episodes of arthritis and lameness may be recurrent. In humans, the different species of Borrelia bacteria induce differing clinical signs, but it is currently unknown whether this is the case in dogs.