Lyme Disease is an illness caused by a spirochete bacteria, Borrelia burgdorferi, which is transmitted to dogs through the bite of infected ticks. The disease has been reported in cats, but the clinical significance is minial. My first three years as a practitioner, I practiced in one of the Lyme Disease hotspots of the world, Long Island, NY. While I diagnosed hundreds of canine Lyme Disease cases, I never once saw the disease in cats. Based on this experience, this article will focus solely on canine Lyme Disease.
Lyme Disease is reported worldwide and throughout the United States. The states of New York, Massachusetts, Connecticut, Rhode Island and New Jersey account for the majority of cases in the United States. However, cases are reported from all geographic regions of the country. Different ticks are carriers in the different regions. Ixodes dammini (the deer tick) in the Northeast and midwest, Ixodes scapularis (the black-legged tick) in the South, Ixodes pacificus (the western black-legged tick) in the West and Amblyomma americanum (the lone star tick) found in several regions are all considered vectors.
There is growing concern that Dermacentor variabilis (the American dog tick) may also be capable of transmitting the disease. Transmission by biting insects (flies, fleas, mosquitos) is speculated but appears to be quite rare. Not all ticks are infected. Infection rates in tick populations vary by tick species and geographic region from as few as two percent to 90 percent or more. Ixodes dammini is responsible for most of the cases of Lyme disease in the northeastern United States. These ticks are found in grassy areas (including lawns), and in brushy, shrubby and woodland sites, even on warm winter days. They prefer areas where some moisture is present. The tick has three life stages: larva, nymph and adult. Each stage takes a single blood meal. They feed on a variety of warm blooded animals including man, dogs, cats, horses and cows. The bite is painless so most victims do not know they have been bitten. The nymphal stage appears to be responsible for most Lyme Disease cases. Both the larval stage (about the size of a grain of sand) and nymphal stage (about the size of a poppy seed) attach to a variety of small mammals, but prefer the white-footed mouse, the main reservoir of the Lyme Disease bacteria. The adult ticks (about the size of a sesame seed) prefer to feed on white-tailed deer. The entire life cycle requires three separate hosts and takes about two years to complete.
Larval and nymphal deer ticks also attach to birds.It is believed that birds may be a primary means by which the infected ticks are spread from one area to another. Some species of birds also function as a reservoir of infection.
Lyme Disease has been reported in many domestic mammals, but as stated above, the scope of this article is Lyme Disease in the canine. Symptoms of disease include fever, lameness and muscle soreness, extreme lethargy, loss of appetite, swollen glands and joints. In advanced cases, oragan systems including the heart, kidneys, liver, eyes and nervous system are potentially affected. Clinical signs may be intermittent and vary in intensity from mild to very severe and can mimic many other conditions. If your dog is experiencing any of the aforementioned signs, it is imperitive that you seek veterinary medical attention ASAP.
The key treatment for Lyme Disease is administration of a tetracycline class of antibiotic. However, supportive care for severe fever, pain, and any secondary organ disfunction is also of great importance. This often requires hospitalization for at least 2 – 5 days.
Prevention of Lyme Disease is very important and reasonably easy. Since Lyme Disease can only be spread thourgh the bite of the tick, elimination of this vector is the solution. Advantix and Frontline are the two most effective tick preventative products on the market. However, since no treatment is fool proof, a regular thorough exam of your dog for the presence of ticks is a good idea. Ticks are most commonly found around the head and neck. They can also be found between the toes, on or in the ears, and in the armpit and groin areas. Because the ticks are so small, it is important to look very carefully. In dogs, the symptoms of Lyme Disease may not develop for several weeks or months following tick bite.
Another effective preventative measure for Lyme Disease is yearly vaccination. In Lyme Disease hotspots, this is strongly recommended. However, since the Lyme Disease vaccine in not 100%, good tick control with Frontline, Advantix, and visual inpection are still a very important aspects of preventing Lyme Disease in dogs.
Here in Florida, due to the current rarity of Lyme Disease in dogs, I do not recommend vaccination. However, as the incidence of Lyme Disease spreads over time, this may change in the future.
By: Roger L. Welton, DVM
President, Maybeck Animal Hospital
Author Canine and Feline 101