Lyme Disease in Dogs: Risk, Testing, Prevention, and Treatment
Lyme Disease: More Common and More Geographic Than Most Owners Realize
Lyme disease (borreliosis), caused by the bacterium Borrelia burgdorferi and transmitted by the black-legged tick (Ixodes scapularis in the East and Midwest, Ixodes pacificus in the West), has expanded its geographic range significantly in recent decades. What was once primarily a Northeast US concern now affects dogs in most of the eastern United States, parts of the upper Midwest, and increasingly in Canada. Dogs in endemic areas face real risk without year-round tick prevention, and a significant percentage of exposed dogs test positive for Lyme antibodies.
How Dogs Get Lyme Disease
Transmission requires a tick to be attached and feeding for approximately 24-48 hours before Borrelia bacteria are transmitted. This means tick checks and prompt removal after outdoor time are genuinely effective prevention (though ticks are small, particularly nymphal-stage ticks which are the most common transmission vector in spring and early summer). Dogs can't transmit Lyme disease to humans, but a tick-infested dog can carry ticks into the home, where they may detach and attach to family members.
Symptoms in Dogs
Many dogs exposed to Lyme never develop clinical illness. In those that do, the most common presentation is recurring lameness affecting one or more joints (often shifting from leg to leg), fever, lethargy, reduced appetite, and lymph node swelling. The classic “bull's eye” rash of human Lyme disease does not occur in dogs due to coat coverage. The more serious complication unique to dogs: Lyme nephritis, a protein-losing nephropathy that can progress to kidney failure. Labs and Golden Retrievers appear particularly susceptible. Any Lyme-positive dog with protein in the urine warrants additional investigation.
Testing and Treatment
The 4Dx or SNAP Lyme test (run at annual wellness visits) detects antibodies to Borrelia. Positive antibody tests confirm exposure but not necessarily active disease — an additional quantitative C6 antibody test and urine protein assessment helps determine if treatment is warranted. Treatment is doxycycline for 28 days; most dogs improve within 3-5 days of starting treatment. Antibiotics clear clinical signs but may not eliminate infection entirely.
Prevention
Year-round tick prevention (Simparica Trio, NexGard, Bravecto, and others) combined with the Lyme vaccine (recommended for dogs in endemic areas) provides the most complete protection. Annual testing allows early identification of exposure.