Canine Borreliosis is caused by a unique germ, a spirochete called Borrelia burgdorfer the name of which is not particularly important. While the disease has been reported in Europe since the early 1900’s, it was firmly diagnosed first in North America 1975 near Lyme, Connecticut, hence the popular name.
The Lyme germs do not survive free-living in the environment. They live only in living ticks and animals. The primary vector for Lyme is the tick Ixodes which is a “hard tick”. These ticks are quite small (less than 3 mm in width) and are commonly referred to as deer ticks because deer are one of their main hosts. Natural infection requires at least 48 hours for the tick to be attached to a dog but once these germs enter a dog’s body, they usually result in a true infection which can be very persistent. The Lyme organism, according to some researchers, can proliferate in a dog’s body for very long times, maybe even the life of the dog. The good news is that most infected dogs never develop any signs of illness. In dogs that do develop illness, the germ likely invades tendons, joints, and other adjoining tissues. The real problem is not the germ itself but the inflammatory response the dog’s body creates as a result of the germ. According to experts, between 5% and 10% of infected dogs actually have symptoms which develop within 2 to 5 months after the tick bite. It is speculated that the dog’s immune system condition plus the number of ticks that bite the dog determine the severity of symptoms.
Typical signs of Lyme Disease are fever, failure to eat, swollen lymph nodes, and sporadic lameness due to arthritis of several joints. In my experience, the typical lameness is of the “shifting” nature, i.e. the dog is lame on more than one leg and favors one then the other over time. Also, I have felt that the arthritis typically starts in a joint that is close to the area of the tick bite although that might have happened months before. There are reports of heart disease as a result of Lyme infections but, in my practice, I have not diagnosed this condition.
An accurate diagnosis of Lyme Disease can be frustrating. First, the dog’s basic blood count and other routine tests are often inconclusive. Secondly, the tests for antibodies (the body’s immune response to an infection) vary in their accuracy. It seems that lots of conditions can give a false positive even in the best laboratories. Of course, if one could actually culture the spirochetes in joint fluid or surrounding tissue, which would be a strong diagnosis but the Lyme germ typically, has fairly low numbers of organisms present. There is a nice test called a “PCR” that is quite accurate. It requires a skin sample from near the tick bite, again which probably happened months ago or maybe some skin from around the joint area that is affected. Joint fluid or even urine may show a positive to Lyme using the PCR test. The problem with the PCR tests is that a negative doesn’t mean the dog does not have Lyme.
Since we struggle to prove the diagnosis, veterinarians often just use the symptoms we see along with the history to make a diagnosis. Then, we give the appropriate antibiotic for the Lyme spirochete and stand back. Sure, we get some good results at times but research documents that many dogs continue to have low-grade infections of the spirochete despite aggressive appropriate treatment.
While there are vaccines available for Lyme Disease, I recommend a long conversation with your local veterinarian about the advantages and disadvantages of Lyme vaccination. There are issues but many veterinarians routinely vaccinate for Lyme Disease.