Lyme Disease in Dogs

Lyme disease is a bacterial infection spread by ticks. It can be found in both dogs and cats. It has been diagnosed all over the United States, but is most common in the eastern coastal states. It can affect many body systems, particularly the joints.

Signs & Symptoms of Lyme Disease

Limping that progresses from mild to severe over time
Swelling of the joints
Swelling of the lymph nodes
Fever of 103°F to 105°F
Loss of appetite
Lethargy
Changes in behavior (confusion, nervousness, seizures, etc.)

If Lyme disease is allowed to progress, kidney disease or kidney failure, heart complications or heart failure, or nervous system disease may develop and become fatal.

Causes of Lyme Disease

Lyme disease is caused by a spirochete bacteria, named Borrelia burgdorferi, that has to be altered inside of a tick’s gut to be transmissable.

Two species of ticks are the prime carriers of B. burgdorferi in the United States:

Ixodes scapularis (common deer tick) in the Northeast and upper Midwest
Ixodes pacificus in the western United States.

These ticks have a life cycle that requires that it overwinter in a different host each time it molts to a new life stage. As larvae, the tick will overwinter inside of a small host, usually a white-footed mouse or bird. If the mouse is infected with the B. burgdorferi bacteria, the tick may pick it up at this stage. The following spring, the tick molts into the nymph stage and finds another larger host to overwinter on. This host could be a deer, dog, or human. If any of these hosts carry the bacteria, ticks can become infected at this stage as well. It may also transmit the bacteria if it picked it up on the mouse the previous year. The spring after this winter, the tick will molt into an adult and latch on to yet another host, which it can infect by regurgitating the bacteria into the host.

Diagnosis of Lyme Disease

Diagnosis always begins with a complete history and a physical exam. It is often difficult to diagnose Lyme disease because most typical tests can show up normal, as most dogs are asymptomatic.

History - If they suspect Lyme disease, your veterinarian will likely inquire about Ixodes tick exposure and bite history.
CBC/Chemistry Panel - These blood tests will evaluate various internal organ functions, including the heart, liver, kidneys, pancreas, metabolism, and electrolyte balance. The CBC is a measure the amount and different kinds of red and white blood cells that are present in the body.
ELISA testing - This stands for "enzyme-linked immunosorbent assay,” and is a test used to determine if a dog has been exposed to a certain pathogen by seeing if the dog’s body has produced antibodies against the pathogen. It can be used to test for viruses, bacteria, microbes, or other material. In this case, the veterinarian would take a blood sample and test the serum for the antibodies to Lyme disease. The ELISA test may be falsely negative if the dog is infected but has not yet formed antibodies, or if it never forms enough antibodies due to a weakened immune system. Some dogs have had the disease for so long that it no longer has enough antibodies to the disease to test positive. Dogs that have been vaccinated for Lyme disease will likely test positive, so this test is not recommended for vaccinated dogs.
Immunofluorescence - This is a technique used to illuminate either viruses or their antibodies in a tissue or culture using a fluorescent dye. In this case, your veterinarian will make a tissue or cell smear and expose it to a specific antibody for Lyme disease. The antibody will attach to any virus displayed in the sample and show under a microscope as a bright green spot on the slide.
Western Blot - This is a very specific test that is usually performed after a positive ELISA or immunofluorescence test to determine if the result was due to a live spirochete transmitted by a tick or a killed bacteria found in the Lyme vaccine. Because many bacteria share proteins, separating the proteins in B. burgdorferi and seeing which ones your dog’s antibodies react to can determine a live infection.
Antibody Test - A test often used after a positive ELISA or immunofluorescence test result is the antibody test. The C6 protein is only found on the live B. burgdorferi bacteria and not on the killed bacteria in the Lyme disease vaccine. Unlike other tests, it is quantitative, economical, and does not cross-react with the Lyme disease vaccine. It can often be done in your veterinarian’s office within minutes.
Qualitative PCR Test - This "polymerase chain reaction" test is a very specific and sensitive DNA test that can be used to look for an agent in a dog or tick’s DNA. It is possible to test for B. burgdorferi in blood, serum, tissue, joint fluid, a tick, or other sources. The blood samples may yield a false positive, and joint fluid seems to be the most accurate way to test using PCR.

Treatment for Lyme Disease

Your veterinarian will likely prescribe an antibiotic to take care of the infection. Antibiotics are usually given for a minimum of 14 days, often as long as 30 days. In severe cases, relapse has been documented even after the 30 days. Often, bacteria are still present in your dog’s body, but the antibiotics regulate it to a level manageable by the immune system.

Prevention of Lyme Disease

Prevention of Lyme disease is achieved by:

Regular use of a flea preventives that protect against ticks as well
Avoid environments frequented by ticks (especially between May and August, though ticks can be active in any temperature above 32°F) and check your dog for ticks after they go outside
Ability to differentiate an Ixodes tick from other ticks may help the veterinarian identify if it is a carrier of Lyme disease.

There is no immunity in recovered dogs, so re-infection is possible. It is possible for humans to get Lyme disease, but not from an infected dog. Lyme disease is spread only by ticks, so check yourself, as well as your dogs, for ticks after having been outside.

Proper removal of ticks

Removing ticks within 24 hours of exposure can greatly reduce the chance of your dog getting Lyme disease. Ticks do, however, carry many other pathogens, and frequent checks and proper removal are crucial to the prevention of disease. If the ticks stay on your dog long enough to get a full blood meal, they will often release themselves and fall off your dog unnoticed.

Use fine point tweezers to remove the tick at the mouthparts, or as close to the skin as possible. Tricks like using petroleum jelly, alcohol, or a match will not cause the tick to back out, and may even cause it to regurgitate more bacteria into your dog. Make sure you pull the mouthparts out slowly and steadily. If you do not remove the head of the tick, it can continue to regurgitate fluid into your dog, potentially transmitting the bacteria causing Lyme disease.
Disinfect the wound on your dog. A triple antibiotic ointment may help the wound heal faster.
After removal, be sure you kill the tick by putting it in a jar of alcohol (this may also help with identification, if need be later). Flushing the tick down the toilet will not kill it. Because you likely removed it before it had a full blood meal, the tick will usually continue to look for another host to feed on, and if it’s carrying Lyme disease, it can transmit the bacteria to others.