Lyme Disease and Pets, What Is the Deal?

Female deer tick

Lyme disease is a potentially serious infection caused by the bacteria Borelia burgedoferi and transmitted by the deer tick or black legged tick, Ixodes scapularis.  In this article, I will attempt to explain the differences and similarities between this disease in people and in dogs, the best preventative measures, and testing and treatment of veterinary patients.

The Northeast United States has the highest incidence of Lyme disease. The Center for Disease Control has collected a great deal of information on the condition as it affects people. The veterinary community also has paid special attention to this infection in recent years, developing a much better understanding of the disease, tests to help us identify affected patients, and preventative measures including highly effective tick control and vaccinations against the bacteria.

Who gets Lyme disease?

Possibly the most striking difference between lyme disease for ourselves and our companion animals is our susceptibility. People are known to develop symptoms of infection 90% of the time after exposure to B. burgdorferi.  Study of the infection in dogs has shown that 95% of the dogs exposed to the bacteria either developed no symptoms or very mild symptoms that resolved without any treatment. Our feline friends seem not to be susceptible to Lyme disease at all.

This difference in susceptibility is also important in diagnostic testing. Lyme disease tests detect a patient’s antibody response to the bacteria. Even though the vast majority of dogs exposed to the bacteria will never develop Lyme disease, they will test positive for these antibodies. For that reason it is not particularly helpful to test asymptomatic dogs. It is also considered by most experts inappropriate and unnecessary to treat dogs who have no symptoms just because they have a positive test result.

What are the symptoms of Lyme disease?

As in people, dogs who develop Lyme disease may have differing symptoms.  Unlike people, dogs do not develop their symptoms acutely. In fact, weeks to months will pass after the bacteria enters their body before any symptoms arise. The most commonly recognized symptoms are joint swelling and pain, fever, and sometimes swollen lymph nodes.  A much more serious, though much rarer, result of infection is a type of kidney disease known as Lyme nephritis.  Our goal is to identify at risk patients by screening for protein loss in the urine. By the time dogs develop symptoms of Lyme nephritis, they are often very sick with loss of appetite, loss of weight, and increased thirst.

After being bitten by a tick many dogs will develop a circle of redness on their skin around the site of the bite. This redness generally takes three days to go away. It does not correlate to a tendency to develop Lyme disease. In most cases, it requires no treatment at all and may go unnoticed on a furry dog. It is also usual for a small bump to develop where the tick bite occurred. This does not necessarily mean that any part of the tick is embedded. If the area has a scab, redness, or warmth indicating active inflammation, it is appropriate to apply antibiotic ointment such as Neosporin to the area.

How is Lyme disease treated?

Treatment for Lyme disease is with antibiotics. Several antibiotic options exist for dogs showing signs of Lyme disease. For the majority of our patients, all symptoms of Lyme disease will resolve within 2 – 3 days of beginning treatment. Experts agree that treatment should be prescribed only for dogs with symptoms.  Though antibiotics are generally safe, the risks of antibiotic resistance and gastrointestinal side effects make treatment of asymptomatic patients inappropriate.

How do I protect my dog from Lyme disease?

No perfect strategy exists but preventing Lyme disease has become easier.  The development of safe, effective, and long-lasting medications to kill ticks as they climb on our pets has dramatically reduced the risk of infection (Advantix, Frontline-Plus, Seresto Collars, Nexguard, Bravecto). The simple procedure of checking for ticks and removing them promptly is also highly effective in reducing disease transmission. For both people and dogs, most infections occur only when ticks are allowed to feed on the patient for more than 48 hours. Lastly, several vaccines are available for dogs at high risk for Lyme disease. Though these vaccines do not provide complete immunity, they do further decrease the risk of infection when used in conjunction with tick control medication and tick removal.