Clean Run Magazine - May 2009 - 81

What Performance Dog Owners Should Know About Tick-borne Diseases By David B. Hyde DVM and Julie A. Roos DVM Part 1 Ticks and tick-borne illnesses are a growing concern all over the United States. Each region has its unique tick-related problems. What does it really mean when your dog is diagnosed with one or more of these diseases? Before we begin, you should know there are many differing opinions in the veterinary world about tick diseases and treatment. Our goal here is to give you the facts and describe some of the more controversial topics so you and your veterinarian can decide what is best for your canine athlete. We’ll cover Lyme disease and anaplasmosis this month, and follow up with erlichiosis and Rocky Mountain Spotted Fever next month, along with general recommendations for treatment and prevention that you can discuss with your veterinarian. Lyme Disease Lyme disease is caused by a spirochete (spiral-shaped) bacteria called Borrelia burgdorferi. Lyme disease was first discovered in 1975 in Lyme, Connecticut. The specific tick that transmits Lyme is called the deer tick. The deer tick is ubiquitous to New England and the East Coast and appears to be spreading. A healthy deer tick population also exists in the upper Midwest. Deer ticks are most commonly found in wooded areas but can be found anywhere, including your backyard. It takes approximately 36-72 hours for Lyme disease to be transmitted from the tick to the dog. Signs of illness, however, may not occur until three to five weeks after exposure to the infected tick. Signs of Lyme disease include fever, joint pain, joint swelling, and lack of appetite. The most interesting point, however, is that most dogs never develop clinical signs at all. In 95% or more of cases, dogs infected with Borrelia bacteria never feel sick and they simply recover on their own. We do not know why some dogs get sick, and others do not. A very small percentage of Lyme-affected dogs get a severe, fatal form of the disease called Lyme nephritis. In these difficult to diagnose cases, the kidney suffers severe damage as a result of the infection. Dogs with Lyme nephritis usually do not survive. Of the 5% of dogs that do feel acutely ill, most are easily treated. Clinical signs usually resolve within 24-48 hours after starting antibiotics. If signs do not resolve, you are probably not dealing with Lyme disease. There is much debate right now on a possible syndrome of chronic Lyme disease. Affected dogs have repeated bouts of joint pain, joint swelling, fever, and inappetence. Chronic Lyme is also blamed for a wide variety of illnesses including cardiovascular disease, seizures, and immune-mediated problems. At this time there is not any substantial scientific evidence to support the chronic Lyme theory, only anecdotal evidence. Currently the test of choice for diagnosing Lyme disease is the SNAP 4DX test (Idexx Corporation), which is positive only after a natural exposure, meaning vaccination does not cause the test to be positive. The test detects antibodies that can be detected 3-5 weeks after infection with Lyme. The antibodies can remain in the blood for years; therefore, the 4DX Lyme test can also remain positive for years. Antibodies are only partial evidence of an infection, not a specific diagnosis. For example, if your dog comes up positive on a 4DX Lyme test, he may have been exposed as early as three weeks ago. However, he May 09 | Clean Run Deer ticks expecting a victim (left), on human skin (right) may also have been exposed to Lyme over a year ago and never developed clinical signs. Remember that 95% of dogs exposed to Lyme disease never display illness. Just because your athlete comes up lame or is off his game does not mean that he has Lyme disease. In our opinion Lyme disease is significantly overdiagnosed because the 4DX test can remain positive for a long time after exposure. Because the 4DX test is relatively non-specific for the diagnosis of Lyme, Idexx Corporation developed a second test that can be run, the C6 quantitative antibody titer test. This test was designed to quantify just how high or low the titer to Lyme is in an individual patient. Sounds like a good idea; however, studies have shown that there is no correlation between the magnitude of the titer and the presence of clinical disease. Therefore, treating a healthy dog for Lyme based on the quantitative C6 test makes no more sense than treating a healthy dog with a positive 4DX test. We advise our clients to do the 4DX Lyme test for two reasons: first, to identify new exposures and treat them if needed; and second, to aid in development of an intelligent vaccine protocol. Several vaccines are available to help prevent Lyme disease. Historically, Lyme vaccines were not well-liked because they were suspected of causing some vaccine reactions. The new generation of vaccines, however, are thought to be safer and better tolerated. If you have Lyme disease in your area, vaccination is recommended. Because no vaccine is 100% effective, it is important to also use effective tick prevention. Talk with your veterinarian about whether Lyme vaccination is a good choice for your dog. 81

Clean Run Magazine - May 2009

Table of Contents for the Digital Edition of Clean Run Magazine - May 2009