Lyme Disease in Dogs

 

By Erika de Papp, DVM, DACVIM

Lyme disease is a very common infectious disease in the northeast United States. It is also a very controversial topic amongst veterinarians because most dogs that test positive are not clinically ill. This makes it difficult to determine which dogs should be treated. Lyme disease also affects humans, so it is a topic of interest to everyone. The purpose of this article is to answer some commonly asked questions about Lyme disease and clear up some common misconceptions.

Lyme disease is caused by the spirochete bacteria Borrelia burgdorferi. The disease is transmitted to humans and dogs by the nymph and adult stages of the black-legged tick, Ixodes scapularis.

In New England, 50-75% of dogs tested may be positive for Lyme disease.

 

If my dog tests positive, does this necessitate treatment?

The answer to this will vary from dog to dog, and remains a point of controversy. Only about 10% of positive dogs will ever develop clinical illness from infection with the Lyme organism, so many veterinarians argue that treatment is not necessary for seemingly healthy dogs. Today we are fortunate to have two Lyme tests that assist us in determining if the infection is active / recent. If your dog tests positive on a screening test, you should discuss additional testing with your veterinarian to determine if treatment is warranted. In endemic areas (including Massachusetts), annual screening tests for Lyme disease are recommended.

If your dog does develop clinical illness from Lyme disease, the most common signs are lameness, fever, lethargy, and enlarged lymph nodes. Clinical illness is expected 2-5 months after infection. The majority of dogs respond very well to antibiotic treatment with Doxycycline or Amoxicillin.

Black-leggged ticks are small, so if I find a large tick on my dog, he/she can’t get Lyme disease, correct?

The larval and nymphal stages of all ticks are small, but an engorged adult tick can be quite large, so a lab would need to identify the tick to be sure your dog has not been bitten by a black-legged tick.

If I find a tick on my dog, should I go to the vet?

If you are comfortable removing the tick, you do not need to see your vet. The best way to remove a tick is to use tweezers to grab the tick as close to the skin as possible. The tick should then be removed by pulling straight out. Do not twist or crush the tick as you are removing it. Wash your hands after removing the tick to limit possible exposure to yourself.

How long does the tick need to be attached to transmit infection?

For Lyme disease to be contracted, the tick must be attached to your dog for at least 48 hours. Therefore, the best means of avoiding Lyme disease is to remove ticks as soon as they are found. Daily inspections of your dog are recommended, especially if they have been in wooded areas.

In addition to “tick checks,” we also strongly recommend topical parasiticides such as Frontline or Advantix (dogs only). There are several other tick products available, so please discuss the appropriate choice with your veterinarian. Be sure to avoid bathing or swimming for 24 hours after application of these topical products. Follow the application guidelines carefully for best efficacy.

Once a frost occurs, I don’t have to worry about ticks anymore until the following spring, correct?

Wrong. Adult ticks are active whenever the weather approaches or exceeds freezing. If there is snow cover, there won’t be much if any tick activity, but if we have several warm winter days in a row, the ticks may be active.

Can I get Lyme disease from my dog?

No, Lyme disease is not a zoonotic disease, meaning it cannot be directly transmitted from your dog to you. However, if a tick crawls off your dog and bites you, you can become infected.

Should I vaccinate my dog against Lyme disease?

There are several canine vaccines available to prevent Lyme disease. The need for this vaccine should be determined on a case by case basis following a discussion with your veterinarian. We recommend that all dogs be tested for Lyme disease before considering a vaccine. Some opponents of vaccination fear that if your dog is vaccinated and still contracts the disease, the symptoms will be worse. However this is based on experience with the human vaccine (no longer on the market), and has not been proven in dogs.

For more information on Dr. de Papp or Angell’s Internal Medicine service, please visit www.angell.org/internalmedicine or call 617-522-7282 to schedule an appointment.