Ask the Vet! Helpful articles from the Precise® Vet, Dr. Lisa Drapela

Your Pet and Lyme Disease

I have been talking with some of the pet owners here at the company about their concerns for their pets. These topics will be discussed in a series of articles on this web site. These articles are in no way meant to replace the advice of your veterinarian. They are meant to supply knowledge because knowledge is empowering. -- Dr. Lisa Your Pet and Lyme Disease Lyme disease (borreliosis) is an infectious, tick-borne disease caused by Borrelia burgdorferi, a type of bacteria called a spirochete because of its corkscrew shape. Lyme disease was first recognized in 1975 when an unusual outbreak of rheumatoid arthritis occurring in children was reported in Lyme, Connecticut. In 1982, the bacteria Borrelia burgdorferi was determined to be the cause of that outbreak. This disease was first recognized in dogs in 1984. As you can see from the map below, only a relatively small portion of the United States is endemic for the disease. This map was obtained from the Centers for Disease Control and Prevention website, which has a large amount of valuable information on this topic.

B. burgdorferi requires a tick as a carrier and those are the Ixodes ticks. This bacterium also requires a population of wildlife to be the intermediate hosts. B. burgdorferi lives in mice, deer, and other small mammals where they replicate without causing these animals to become sick. When a new tick feeds on infected wildlife, the tick picks up the bacteria that are then transmitted to another animal the next time the tick feeds. For a tick to transmit the bacteria, it must be attached to the host for at least 48 hours. If a tick dies or is removed within this 48-hour period, transmission of the bacteria will not occur. Even if a tick is a carrier of B. burgdorferi and it attaches to the dog for more than 48 hours, the dog may not contract the disease. Some studies indicate that bitches that become infected while pregnant can transmit infection to their fetuses. Clinical Signs Clinical illness usually occurs two to five months after initial exposure, and the likelihood and the severity of the disease seem to vary with the animal's age and immune status. Cats can develop Lyme disease, but it occurs rarely in them, even in endemic areas. Other domestic animals such as horses have contracted Lyme disease, but it does not appear to be a significant problem. The first stage of human Lyme disease, a skin rash called erythema chronica migrans, is rarely seen in dogs. Dogs show several different forms of the disease, but by far the most common symptoms are a fever of between 103 and 105 degrees, shifting leg lameness, swelling in one or more joints, lethargy, and loss of appetite. Dogs show sudden lameness and sometimes signs of severe pain. Joints are often swollen, hot, and painful on manipulation. Lameness may recur after a period of several weeks' recovery. Arthritis to the affected joints may be a result of incomplete treatment or no treatment. A few dogs have developed severe progressive renal disease as a result of Lyme disease. This severe kidney failure is nonresponsive to treatment and death is often the outcome but fortunately, this form appears to be rare. Diagnosis The standard blood test (ELISA) detects antibodies made by the dog in response to infection with B. burgdorferi. This means that the test is not very specific. Dogs that are exposed to the organism but fight the infection off on their own will show a positive test as well as vaccinated dogs. However, the test can be used along with several other criteria to gain a positive diagnosis. Suspected animals should have a history of tick exposure, compatible clinical signs, and have a rapid response to antibiotic therapy along with the positive ELISA testing in order to make a more positive diagnosis. The western blot is a technique that determines antibodies against multiple antigens of B. burgdorferi. This test can distinguish between dogs that have been or are infected and dogs that have been vaccinated against Lyme disease. It can also detect the dog that has been both infected and vaccinated. The ELISA test is a quantitative determination of all the antibodies produced against many antigenic components of B. burgdorferi. The western blot determines the unique pattern of antibodies produced against antigens of a tick-induced infection, which is different from the pattern produced following vaccination. This test is more expensive than the standard ELISA test. Treatment Treatment for Lyme disease is fairly straightforward and consists of using either a tetracycline or penicillin-based antibiotic. Several tetracyclines, such as doxycycline, and penicillin-like antibiotics, including amoxicillin and ceftriaxone, are very effective. Because B. burgdorferi has the tendency to persist in dogs, antibiotics should be given for three or four weeks, even though a beneficial effect can be seen after a few days of treatment. The long duration of therapy is also warranted because this organism multiplies very slowly. It can take 12 hours or more to double in number as opposed to minutes like most other bacteria. However, some preliminary studies show that some animals may not even clear the organism after 30 days and will relapse once the antibiotic is discontinued. In these cases, the animal may have to be on the antibiotic for much longer. It appears that some animals may never completely rid themselves of B. burgdorferi despite aggressive treatment. These animals may suffer from increased degenerative changes in the joints leading to premature arthritis. Prevention There are two approaches to preventing infection in dogs. One is to control the tick population by using tick repellents and/or grooming daily. The other is vaccination. Attempts to reduce the deer tick population by radically reducing the deer population have been only somewhat successful because other wildlife can replace the deer as hosts. Selective chemical control of ticks in areas appears to be more promising, although only small areas can be covered. Tick control is probably the most important thing an owner can do to prevent Lyme disease in their pet. Ticks carry many other diseases besides Lyme disease. By preventing ticks from attaching to your pet, you will be preventing more than just Lyme disease. Avoiding areas of high tick infestation during periods when ticks are active is one of the best ways to avoid contact. Using insecticides on the dog that repel ticks is another method. With the introduction of once-a-month topical insecticides, tick control has gotten easier and more effective. Please read the labels carefully because some products are not meant for cats. Studies have shown that amitraz collars are very effective at preventing transmission of B. burgdorferi. Amitraz is an organophosphate that is very effective at repelling and killing ticks but has little effect on fleas. Despite the claims made by many products to be effective against ticks, do not be fooled. Ticks are very tough and hard to kill. There are several whole-cell, killed vaccines on the market that are licensed for use in the dog, but total protection through vaccination is difficult. One reason is that a strain of Borrelia bacteria can mutate into a different strain. Unfortunately, antibodies made in response to one strain will not always be able to kill a different strain. In addition, if an animal is previously infected with the disease, the vaccine will not offer any protection. These facts coupled with the relatively long incubation period (up to 5 months) contribute to the failure of some of these vaccines in preventing disease. If you would like more information, you can search the web site for the Centers for Disease Control and Prevention. If you are concerned about your pet's protection, contact your veterinarian. They can help you tailor a prevention program to suit your pet specifically.

References

Elfassy OJ, Goodman FW, Levy SA, Carter LL. "Efficacy of an amitraz-impregnated collar in preventing transmission of Borrelia burgdorferi by adult Ixodes scapularis to dogs." Journal of the American Veterinary Medical Association 2001 Jul 15;219(2):185-9. Grauer GF, Burgess EC, Cooley AJ, Hagee JH. "Renal lesions associated with Borrelia burgdorferi infection in a dog." Journal of the American Veterinary Medical Association 1988 Jul 15;193(2):237-9. Gustafson JM, Burgess EC, Wachal MD, Steinberg H. "Intrauterine transmission of Borrelia burgdorferi in dogs." American Journal of Veterinary Research 1993 June;54(6):882-90. Levy SA. "Veterinarians still faced with difficulty in diagnosing Lyme disease." DVM Magazine. Magnarelli LA, Anderson JF, Schreier AB, Ficke CM. "Clinical and serologic studies of canine borreliosis." Journal of the American Veterinary Medical Association 1987 Nov 1;191(9):1089-94. Sheets JT, Rossi, CA, Kearney BJ, Moore GE. "Evaluation of a commercial enzyme-linked immunosorbent assay for detection of Borrelia burgdorferi exposure in dogs." Journal of the American Veterinary Medical Association 2000 May 1;216(9):1418-22. Straubinger RK, Straubinger AF, Summers BA, Jacobson RH, Erb HN. "Clinical manifestations, pathogenesis, and effect of antibiotic treatment on Lyme borreliosis in dogs." Wein Klin Wochenschr 1998 Dec 23;110(24):874-81. Straubinger RK, Summers BA, Chang YF, Appel MJ. "Persistence of Borrelia burgdorferi in experimentally infected dogs after antibiotic treatment." Journal of Clinical Microbiology 1997 Jan;35(1):111-6.

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