Lyme Disease in Dogs

by Nina Beyer, VMD 

Nina Beyer, VMD can be reached at Greenfields Veterinary Associates, 400 Parkville Rd. P.O. Box 189, Mantua, NJ 08051, 856-848-0020 . fax 856-468-3255

Lyme disease (borreliosis), can affect dogs, people, horses, cats (who seem to have natural resistance), and other animals. The only tick that transmits the disease in our region, Ixodes scapularis, is about the size of a pinhead or smaller and is nearly impossible to find on a dog.

It has a 3-stage life cycle, each capable of transmitting Borrelia, and a 2-3 year life span. Larva and nymph stages feed on small mammals, while adults (called “deer ticks”) feed on larger mammals. Other ticks and insects can harbor Borrelia but it can only be transmitted through the bite of an infected tick. (It can’t be “caught” from contact with dogs or other animals.)

Only a small percentage of infected dogs will develop signs of illness, usually 2-5 months after infection, but they may go unnoticed because they are subtle and often temporary. Most dogs develop lameness, but some may develop fever, listlessness, lack of appetite, swollen joints or lymph nodes. Lameness may be intermittent or shift from leg to leg.

Dogs with positive test results but no symptoms may not develop problems later. Definite diagnosis is next to impossible, but we feel pretty confident if the blood test is positive and the patient gets better rapidly when we start treatment with antibiotics. For pain, we also give anti-inflammatory medications and recommend rest. Most limping stops within three days. After the course of treatment, if the titer is holding steady or decreasing, we can be pretty certain that treatment has worked. If it is higher, we give a longer course of the antibiotic.

The logical way to keep our dogs from getting Lyme disease is to limit exposure. Unfortunately, these ticks aren’t just found in the woods; they like bushes and grassy, overgrown areas, and are very common in our region. Repellents can be applied to the dog’s yard, but overuse can make the dog sick. Topical insecticides work, but not 100%. The amitraz tick collar works extremely well but shouldn’t be used with certain other medications, and is very toxic if swallowed. Though it is sold over the counter at pet supply stores, ALWAYS check with your veterinarian before use!

The two forms of vaccine to prevent Lyme disease are very controversial. They are effective at providing immunity for up to six months for one or more strains of Borrelia (given by injection). No one knows if these vaccines can protect for a year or longer against natural exposure by tick bite. Also, because we know that much of the pathology of the disease is caused by the patient’s immune system reacting to the presence of the organism, some authorities worry that the immune system will cause signs of disease where there weren’t any before. Also, once your dog has been given the Lyme vaccine, he will always have a positive titer and your veterinarian would have to ask the laboratory to do a different type of test to tell the difference between the antibodies caused by the vaccine and by the bacteria. This test costs about two-and-a-half times as much, and can’t differentiate between recent exposure versus exposure in the distant past, or exposure to pathogenic versus nonpathogenic strains.