Healthy Dogs

Lyme Disease in Dogs (Canine Lyme Disease)

Lyme disease is caused by the spirochete bacteria Borrelia burgdorferi. The spirochete is acquired through the bite of an infected tick. Lyme disease is now regarded as the most common tick-borne illness in the United States.

This disease was first recognized in 1975, following an outbreak of what appeared to be acute arthritis in several rural communities in southeastern Connecticut, including the town of Old Lyme. Currently, most cases are found in wooded locations in the Northeast, upper Midwest (including much of Wisconsin and Minnesota), northern California, and the Pacific Northwest.

The white-footed mouse is the principal reservoir for the spirochete. Birds can also harbor it. The white-tailed deer supports the tick, but not the spirochete. Lyme disease is spread primarily during tick season (May through August), peaking in the month of July, but ticks can be active any time the temperature is over 32°F (0°C).

The disease in dogs is most commonly characterized by the sudden onset of lameness. In fact, lameness is often the only sign of infection. One or more joints may become swollen and painful to the touch. Some dogs run a fever and experience weakness, lethargy, loss of appetite, and weight loss. The lameness may last only a few days, but in some cases it becomes chronic and persists or recurs for months.

Kidney problems are the next most common sign. An acute cardiac syndrome is quite rare. Both of these syndromes are usually fatal.

Most dogs exposed to Lyme disease do not become ill. Serological blood tests will indicate whether a dog has been exposed to the disease. Dogs may not test positive until a few weeks after exposure. New serologic tests can distinguish between dogs with vaccine immunity and dogs with natural exposure. A rising antibody titer in the absence of recent vaccination, however, indicates active infection. Western Blot and ELISA blood tests are now both used to detect exposure. Many dogs who test positive for Lyme disease will also have other tick-borne diseases, such as ehrlichiosis and babesiosis.