Limping dogs, often running a fever, are common visitors at the Animal Clinic at Thorndale. One of the prime infectious diseases in our Downingtown, PA, location, that causes swollen painful joints, is Lyme disease. A very large number of dogs in Chester County have had exposure to the Lyme causing bacteria, carried by the ticks that frequent our forests and grasslands. Not all dogs that test positive for a Lyme exposure will be symptomatic for Lyme disease. When your dog does test positive to Lyme exposure, our doctors will discuss with you whether or not treatment is warranted. Unfortunately, we have also seen the potentially fatal form of Lyme disease too frequently in our hospital. This Lyme nephropathy, or Lyme induced kidney disease, is much more difficult to treat. The Animal Clinic at Thorndale offers routine testing for Lyme exposure in a combination test that also looks for heartworm, anaplasmosis, and ehrlichia. We can test for all 4 diseases with just a few drops of your dog’s blood.
Lyme Disease is caused by a spirochete called Borrelia. A spirochete is a type of bacterium. It is transmitted to dogs through the bite of a tick. Once in the blood stream, it is carried to many parts of the body. It is especially likely to localize in joints.
It was first thought that only a few types of ticks could transmit this disease, but now it appears that several common species may be involved.
Lyme Disease is named after the city in which it was first discovered, Old Lyme, Connecticut. Thus, it is called “Lyme Disease” and not “Lyme’s” Disease.
Also a Disease of Humans
Humans also get Lyme disease; however they do not get it directly from dogs. They get it from being bitten by the same ticks that transmit it to dogs. Therefore, preventing exposure to ticks is important for you and your dog.
Clinical Signs
Many people having the disease develop a characteristic bull’s eye rash at the site of the bite within 3 to 30 days. For these people, the disease can often be easily diagnosed at an early stage. However, symptoms of Lyme Disease are more difficult to detect in animals than in people.
This characteristic rash does not seem to develop in dogs or cats. Because the other symptoms of the disease may be delayed or not recognized, and because the symptoms are similar to those of many other diseases, Lyme Disease in animals is one of many diseases that may be causing similar problems.
Many dogs affected with Lyme Disease are taken to a veterinarian because they seem to be experiencing generalized pain and or have stopped eating. Affected dogs have been described as if they were “walking on eggshells.” Lameness may involve multiple limbs, the back may be hunched and joints may be visibly swollen. Often these animals have high fevers. This painful lameness often appears suddenly and may shift from one leg to another. If untreated, it may eventually disappear, only to recur weeks or months later.
Some pets are affected with the Lyme Disease organism for over a year before they finally show symptoms. By this time, the disease may be quite widespread in the body. Other forms of Lyme disease have been reported in dogs, such as neurologic problems, similar to the facial paralysis (Bell’s Palsy) that can be seen in humans.
A rare, but potentially fatal, form of Lyme disease may attack the kidneys of dogs. This “Lyme nephropathy” often presents itself as a dog drinking more water than normal, urinating larger volumes, decreased appetite, possibly vomiting, and weight loss. The retriever breeds appear to be more predisposed to this form of Lyme disease, but it can occur in any dog. This form of Lyme disease requires prompt recognition and treatment because the kidney failure is rapidly progressive in most cases.
Diagnosis
Dogs with lameness, swollen joints, and fever are suspected of having Lyme Disease. However, other diseases may also cause these symptoms. There are three blood tests than may be used for confirmation. The first is a screening for antibody test. This test does not detect the actual spirochete in the blood but detects the presence of antibodies created by a exposure to the organism. A test can be falsely negative if the dog is infected but has not yet formed antibodies, or if it never forms enough antibodies to cause a positive reaction. This may occur in animals with suppressed immune systems. Some dogs that have been infected for long periods of time may no longer have enough antibodies present to be detected by the test. Therefore, a positive test is meaningful, but a negative is not.
It is important to understand that many dogs who have had an exposure to Lyme causing bacteria, and therefore test positive on this screening test, may never actually develop signs of the disease. The decision whether to treat your dog for Lyme disease if it tests positive on an antibody test needs to be made in a discussion with your veterinarian. Even dogs that have been treated for Lyme disease in the past may continue to test positive on an antibody test for years after treatment. This screening antibody test is simply a “yes” or “no” test, antibodies present or not.
A second test, called a quantitative C6 antibody test, will quantify the level of antibodies in the dog’s blood stream. Dogs with low antibody titers are either in very early stages of infection or do not have significant exposure to the bacterium to cause antibody production. A high titer more likely corresponds with active ongoing infection. If a dogs has signs of Lyme disease and a high C6 titer at diagnosis, that titer should gradually decline following treatment. In 6 months following treatment, the C6 titer should be less than 1/2 of what is was initially, indicating effective treatment. If the dog presents years later with a high C6 titer, it would indicate another infection or a recrudescence of the original infection has occurred. Following the waxing and waning of the quantitative C6 titer can give an approximate assessment of the dog’s ongoing Lyme exposure.
The third test is the polymerase chain reaction (PCR) test. This is also known as DNA testing. It is very specific and sensitive. If the bacterium is circulating in the sample drawn (blood or joint fluid), the PCR test will be positive for the bacterium. However, not all dogs have the spirochete in their blood cells. If a blood sample is tested, a false negative may occur. The best sample for testing is the fluid from an affected joint. This often requires sedation.
Treatment
Because the Lyme spirochete is a bacterium, it can be controlled by antibiotics. However, a lengthy course of treatment is necessary to completely eradicate the organism. Most dogs will receive an antibiotic, usually doxycycline, for a 30 day treatment course.
The initial antibiotic selected to treat an infected pet may not be effective against the disease, especially if the infection is long-standing. In this situation, a switch to another antibiotic is often effective. Occasionally, the initial infection will recur, or the pet will become reinfected after being bitten by another infected tick.
Prevention
The key to prevention is keeping your dog from being exposed to ticks. Ticks are found in grassy, wooded, and sandy areas. They find their way onto an animal by climbing to the top of a leaf, blade of grass, or short tree (especially Cedar trees). Here they wait until their sensors detect a close-by animal on which to crawl or drop.
Keeping animals from thick underbrush reduces their exposure to ticks. Dogs should be kept on trails when walked near wooded or tall grass areas.
Flea and Tick spot on products can help reduce exposure to Lyme and other tick borne illnesses. In severe infestations, tick collars are also helpful, but should be removed once the exposure has subsided due to their inherent toxicity. If you have cats, be very certain only to use cat-safe products even on your dogs. Cats have been inadvertently poisoned by close contact with dogs being treated with dog-approved only products.
Removing a Tick from Your Dog
Check your pet immediately after it has been in a tick-infected area. If you find a tick moving on your pet, the tick has not fed. Remove the tick promptly and place it in rubbing alcohol or crush it between two solid surfaces. Combing through your dog’s hair coat with a fine tooth comb, such as a flea comb, can often catch many ticks before they can attach.
If you find a tick attached to your pet, grasp the tick with fine tweezers or your finger nails near the dog’s skin and firmly pull it straight out. You may need another person to help restrain your dog. Removing the tick quickly is important since the disease is not transmitted until the tick has fed for approximately 12 hours. If you crush the tick, do not get the tick’s contents, including blood, on your skin. The spirochete that causes Lyme Disease can pass through a wound or cut in your skin.
Vaccination
Vaccines are available for protecting dogs against Lyme Disease. The vaccine is initially given twice, at two or three week intervals. Annual revaccination is also necessary to maintain immunity. The vaccine has been shown to be safe and about 60-80% effective. This vaccine is most appropriate for dogs that have high rates of exposure to ticks and who have not previously contracted Lyme disease. Studies suggest that some dogs which have the vaccine and contract Lyme disease may be more predisposed to develop the potentially fatal kidney form of the disease. Various veterinary professionals have differences of opinion as to the risk/benefits of the Lyme vaccine so be certain to discuss this carefully with your veterinarian.