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Summary
Lyme disease is an infectious illness initiated by a bacterium known as Borrellia burgdorferi. Carried by the Ixodes species, this bacterium leads to Lyme disease in dogs and humans (and less commonly, in cats, horses and cattle).
Meanwhile, many wildlife species can become subclinically infected, meaning that while they don't become sick as a result of these bacteria, they can nonetheless serve as reservoir of infection (via tick bite). This vast source of intermediaries in the transmission of the bacterium probably explains why Lyme disease is the most common tick-borne infection among humans and among the most common in dogs.
The ticks that carry the Borrellia bacteria between wildlife species and pets will infect them after a prolonged period of attachment. Ticks must be attached for more than twelve hours before they can even begin to transmit the bacteria that cause Lyme disease. Many researchers believe that attachment must continue for a minimum of 48 hours before the bacteria can be transmitted.
Because the tick plays so vital a role in Lyme disease, the presence of this disease is confined to geographic locales where the tick is present. The Northeast of the US is the primary endemic location but the entire East coast, the South, the Midwest, and even Northern California may harbor ticks with a capacity to spread this disease.
Symptoms and Identification
Unfortunately, Lyme disease doesn't offer owners or veterinarians a very consistent set of symptoms.
In humans, Lyme disease is famous for the target-sign rash it leaves behind on 80% of its victims' skin, along with a fever and flu-like symptoms in many cases. Joint pain (as a result of immune-mediated arthritis) is also common (in about 60% of patients). Neurological and cardiac manifestations are less common but observed in 15% and 5% of sufferers, respectively. All these signs typically appear within days to weeks of transmission.
In dogs, however, the signs are very different, primarily in that no rash is observed and the signs take longer to manifest -- weeks to months after infection.
In dogs, the most common clinical sign observed involves joint pain. A fever may also result. Neurological and cardiac signs are not a typical feature of this disease in dogs. Kidney disease, instead, is the most common long-term threat Lyme disease poses to the canine patient.
After a patient with these symptoms is identified, they should be tested to confirm the presence of the causative organism (Borrellia burgdorferi). The trouble is, however, that the organism is not easily identified. That is, until recently, when a very specific blood test was devised to identify specific antibodies against a Lyme-causing organism. This now-popular test is available in many animal hospitals located within Lyme-endemic areas.
Unfortunately, this test cannot distinguish between an active infection and simple exposure to the Lyme-causing bacteria. It also has the down-side of not being able to detect these specific antibodies for three to five weeks after exposure.
Since definitive diagnosis often proves elusive, many veterinarians will elect to initiate therapy. Dogs with Lyme disease or similar infections also spread by ticks will usually respond positively within 48 hours. In many cases, clinical improvement is the most effective form of diagnosis.
Dogs with a positive antibody test for Lyme disease should have their urine tested annually for the possibility of renal disease as a result of the long-term exposure to the organism.
Affected Breeds
Any breed of dog can be infected by the bacteria that cause Lyme disease.
Treatment
Treatment of Lyme disease is fairly simply achieved with a course of antibiotics. Doxycycline is the current drug of choice but amoxicillin is often be effective as well. The symptoms will typically recede rapidly after initiating antibiotic therapy.
Unfortunately, antibiotic therapy will not completely eradicate the bacteria that causes Lyme disease -- not, at least, in most cases. Therapy merely helps achieve a state in which the bacteria are hiding and effectively dormant within the infected animal.
Dogs who suffer kidney disease (typically as a result of this long-term latency where the animal's immune system attempts repeatedly to rid itself of the organism) require treatment targeted to this specific manifestation of the disease.
Veterinary Cost
Because it is inexpensively diagnosed and treated, the cost of Lyme disease is not considered especially high. However, the small percentage of dogs whose kidneys are affected may require more intensive treatment later on in their lives.
Prevention
Prevention is the mainstay of Lyme disease management. Preventing tick bites is the only sure means of prevention, but that can be a difficult task without the assistance of tick control products.
Several effective tick control products are available, including the Preventic(R) collar, Advantix(R), Frontline(R), and Revolution(R). Though they may not always prevent attachment or kill the ticks, all of these products will typically cause a tick to detach before the crucial 48-hour timeframe.
Vaccination against the bacteria that lead to Lyme disease is possible and currently recommendable for most at-risk dogs living in Lyme-endemic locations.
References
ACVIM Small Animal Consensus Statement on Lyme Disease inDogs: Diagnosis, Treatment, and Prevention. J Vet Intern Med. 2006; 20:422-434
Cerri D, Farina R, Andreani E, et al. Experimental infection of dogs with Borrelia burgdorferi. Res Vet Sci 1994;57: 256-258.
Greene RT, Levine JF, Breitschwerdt EB, et al. Clinical and serologic evaluations of induced Borrelia burgdorferi infection in dogs. Am J Vet Res 1988;49:752-757.
Kornblatt AN, Urband PH, Steere AC. Arthritis caused by Borrelia burgdorferi in dogs. JAVMA 1985;186:960-964.
Levy SA, Magnarelli LA. Relationship between development of antibodies to Borrelia burgdorferi in dogs and the subsequent development of limb/joint borreliosis. JAVMA 1992; 200:344-347.
Straubinger RK, Straubinger AF, Summers BA, et al. Clinical manifestations, pathogenesis, and effect of antibiotic treatment on Lyme borreliosis in dogs. Wien Klin Wochenschr 1998;110:874-881.
Straubinger RK, Straubinger AF, Harter L, et al. Borrelia burgdorferi migrates into joint capsules and causes an up-regulation of interleukin-8 in synovial membranes of dogs experimentally infected with ticks. Infect Immun 1997;65:1273-1285
Susta L, Uhl EW, Grosenbaugh DA, Krimer PM. Synovial lesions in experimental canine Lyme borreliosis. Vet Pathol. 2012 May;49(3):453-61. doi: 10.1177/0300985811424754. Epub 2011 Nov 10.