This section is on Lyme Disease. If you have any questions concerning the information presented please feel free to email me.
IMPORTANCE OF DISEASE AND STATISTICS:
In the United States, Lyme Disease is now the most common vector-borne infection, and is also a very common disease in Europe, China, Japan, and Australia. In the U.S. it is most prevalent on the Atlantic Coast. Although no cases have been reported in wildlife, both horses and dogs as well as humans can develop the disease. From the CDC Mortality and Morbidity Report, incidences of human infection in the United States (I am sorry I have no data for other countries) with the disease were reported as:
Prior to 1991 -- Not reported
1991 -- 8,764 in U.S. 14 in Ga
1992 -- 7,777 in U.S. 23 in Ga
1993 -- 7,540 in U.S. 43 in Ga
1994 -- 11,030 in U.S. 106 in Ga
1995 -- 8,042 in U.S. 14 in Ga
SCIENTIFIC NAME OF PATHOGEN:
The disease causing agent of Lyme Disease is Borrelia burgdorferi. Three different strains exist in the various geographical locales. In the U.S. Borrelia burgdorferi sensu stricto is the only identified strain. In the Europe, Japan, and Australia Borrelia garinii and Borrelia afzelli (new species names given to the strains of Borrelia burgdorferi in these countries) are the primary strains. Each strain is capable of infecting both humans and animals, and they cause similar symptoms.
DESCRIPTION OF DISEASE -CAUSING AGENT:
Borrelia burgdorferi is a spirochete, i.e., an helical (or spiral) shaped bacteria which is 11- 39 �m long and about 0.2 �m wide. It has an outer sheath, axial filaments, multiple endoflagella and exhibits great motility. This species stains with acid and aniline dyes and by silver impregnation, and it is gram negative.
INCUBATION PERIOD:
Highly variable. Anywhere from 3 days to 4 weeks can elapse between the tick bite and the onset of symptoms. It is suspected that it takes at least 24 hours for transmission of the spirochete from the tick to the host.HUMAN -- SYMPTOMS OF DISEASE: (see Definitions at bottom of the page for unknown terms)
Lyme Disease occurs in three stages. Each of which have their own characteristic symptoms.STAGE ONE: localized infection (from days to weeks after tick bite)
STAGE TWO: disseminated infection (from weeks to months after initial infection)
NOTE: Those examples given in parentheses are the most common. The other areas of disseminated infection show other less common symptoms which vary greatly between individuals and host species.
STAGE THREE: (late infection that has become persistent)
NOTE: These symptoms can all be present, only one be present, or any combination be present. Lyme disease is similar to syphilis in its multisystem involvement, occurrence in stages, and mimicry of other common diseases. Because Lyme disease has only recently been identified as a disease, much is still being learned about the manifestations of this infection. Animals primarily exhibit symptoms affecting the cardiovascular, neuromuscular, and skeletal systems.
HUMAN -- MODE OF SPREAD:
Lyme disease is a vector-borne disease and is solely spread by ticks. The ticks that can spread this disease belong to the Ixodes ricinus complex. These species include I. dammini (also known as I. scapularis ) in northeastern and midwestern U.S., I. pacificus in western U.S., I. ricinus in Europe, and I. persulcatus in Asia. All of these ticks feed and can transmit the spirochete at three different stages -- larva, nymph, and adult. In most of the U.S., I. dammini is the primary vector. Its preferred larval and nymphal host is the white-footed mouse Peromyscus leucopus. The rodent host is tolerant to infection and so acts as a reservoir for the spirochete. The adult tick prefers the white-tailed deer Odocoileus virginianus. Despite their host preference, all three feeding stages will also feed on humans, dogs, horses, etc., and, thus, transmission of the disease-causing spirochete occurs.
HUMAN -- PREVENTION:
A vaccine has been developed for dogs that will protect them against infection. Yearly boosters are required. So far no such preventative measure has become available for human. Because of the maintained natural reservoir for the spirochete in rodents and deer, theoretically the most effective prevention would not be to eradicate the spirochete but to inhibit transmission from the wild population to humans (and dogs, horses, etc.). Tick control and/or eradication is extremely difficult, however, especially considering the infectious potential of all three feeding stages. Therefore, presently the most promising means of prevention is personal protection. Wearing long clothes, covering clothes and exposed skin areas with DEET or permethrin containing insecticides, and checking thoroughly for tick bites is the suggested routine. Only about 1.2% of recognized tick bites cause Lyme disease because it usually takes 24-48 hours for transmission. For those with suspicious tick bites, or just for good measure, a 10 day antibiotic treatment will prevent the spirochete from infecting the human or animal host.HUMAN -- TREATMENT AND CURE:
Luckily, once diagnosed, Lyme disease readily responds to several common antibiotics. Initially, penicillin was the drug of choice, but now either doxycycline or amoxicillin is. For early infections, 10 days is usually sufficient. Infections in stage two require 20-30 days of antibiotics, and stage three infections require specialized treatments usually involving intravenous therapy and are specific to the particular manifested symptoms. Most problems arise, however, not in the treatment but in the diagnosis of Lyme disease. Most serological tests, such as ELISA and western blot, show a good percentage of false-positives and false-negatives and do not distinguish between active and inactive infections. Consequently, patients with other diseases that have similar symptoms may be incorrectly diagnosed with Lyme disease, and vice versa. Thus, serological tests alone often lead to inaccurate diagnoses. Test results must be put in combination with clinical symptoms and likelihood of exposure before an educated diagnosis can be made. A new clinical tests utilizing PCR (DNA identification technique that was so controversial in the O.J. Simpson trial) to detect Borrelia DNA has shown promise and is currently being developed.
DOG -- EXPOSURE AND PREVENTION:
In the southeast United States the Ixodes tick responsible for transmitting Lyme disease has a very low rate of infection, often < 1% of the adults and nymphs. All three stages of tick life cycle -- adult, larval and nymph can infect. Transmission of the infectious agent occurs only after engorgement and, thus, the probability of infection increases the longer the tick remains attached. Current research suggests little danger of infection if the tick remains on the body less than 12 hours. Thus, the best prevention is regular, routine, and thorough examination for ticks and the prompt removal of any found. Ticks are not just found in the woods or near wooded areas so "city" dogs should be checked just like "country" dogs. Currently a vaccine exists for the prevention of Lyme disease in dogs. It is a relatively new product, and, thus, its long term efficacy has yet to be established. It has proven thus far to give protection against infection. The vaccination schedule consists of two initial doses about 2 to 3 weeks apart followed by yearly boosters. The vaccinations can be given to any dog over the age of 14 weeks. Current recommendations are to strongly urge all dog owners in the Northeast and Midwest to vaccinate. In other areas of the country the owner must evaluate risk of exposure to decide if vaccination is warranted. The best prevention, however, is still to prevent tick exposure and to promptly remove any ticks.
DOG -- SIGNS TO WATCH FOR:
Lyme Disease is a multisystems disease that has a wide variety of symptoms that often mimic other diseases. Therefore, these signs alone do not mean that your dog has Lyme Disease. However, if tick exposure has occurred and these signs develop the possibility of Lyme Disease should be considered. Unfortunately, this is a relatively new disease and many older veterinarians especially in the southern United States are not as aware of this disease as they should be. Do not hesitate to suggest to your vet and even insist that testing for Lyme disease be done if you suspect your dog may have it. Remember vets only see your pets a few times a year for 30 minutes or an hour at a time. You live "round-the-clock" with them. You are your vet's best source of information and suggestions about your dog. Any good vet will heed your concerns.
When the dog is first infected, it will run a slight fever, feel lethargic, may not eat, in short what veterinarians (at least those in the south) refer to as ADR -- ain't doin' right. This is an extremely vague condition and often even the most perceptive of us will miss this. So don�t count on this to signal an infection.
After a few weeks to several months (it varies from case to case) most dogs develop arthritis that usually shifts legs, muscle pains, and fever. Rarer signs include inflammation of the heart, complete heart block, seizures, and kidney inflammation. Lameness with no history of trauma is the most common clinical sign.
DOG -- DIAGNOSIS AND TREATMENT:
Unfortunately, there are no current tests for Lyme Disease that do not give high number of false positives and false negatives. This means that if your dog tests positive for Lyme Disease but has shown no signs then he is probably okay. Just to be safe a routine 10 day amoxicillin schedule is recommended. If the dog tests negative but has signs and a history of exposure, aggressive treatment of higher dose antibiotics for longer period of time should still be initiated because the dog is probably infected. Never base or allow your vet to base the decision about infection status on the current tests alone. No matter what you are told there is no completely or even reasonably reliable tests currently available. There is a test currently under development that will hopefully be available in the near future that is much more reliable. History and signs in addition to tests must be considered.
Fortunately, Lyme Disease infections caught early enough (6 months to a year) respond very well to antibiotic therapy. Usually, an high dose of amoxicillin, tetracycline, or any comparable antibiotic for three to four week is sufficient to clear the infection. There have been some cases of recurring infections but that has primarily been in people. Once the disease has reached the chronic stage though, prognosis is much worse for eliminating the infection. Usually, one can only treat the symptoms at this stage.
SUMMARY :
Signs : ADR, **Lameness ** particularly shifting leg lameness, Muscle Pain, Arthritis, Poor Appetite
Prevention : Keep ticks off, Remove ticks ASAP, Vaccinate
Treatment: Early stages -- high levels of antibiotics; Late stages -- varies with the symptoms; Especially for people but some suggest for dogs as well, if any exposure to ticks for greater than 12 hours occurs automatically put on a 10 day amoxicillin regimen.
REMEMBER: Lyme Disease is NOT prevalent other than the Northeast United States (I have no data for other countries) so many vets and doctors are likely to NOT think of it as a probable cause of these signs. Please, please suggest and even insist that they consider it if you feel the circumstances indicate a possible Lyme Disease infection. There are numerous cases in which diagnosis and treatment was delayed months and even years because Lyme Disease was not considered.
DEFINITIONS:
WORKS REFERENCED:
(1) Adelbus, Edward A; Brooks, Geo. F.; Butel, Janet S.; Jawetz, Ernest; Melnick, Joseph L.; and Ornston, L. Nicholas. Medical Microbiology. Appleton and Lange. Norwalk, Connecticut: 1995.
(2) Anderson, Kenneth N.; Anderson, Lois E.; and Glanze, Walter D. Mosby's Medical, Nursing, and Allied Health Dictionary . Mosby-Year Book, Inc. St. Louis, Missouri: 1994.
(3) Halperin, J.J. MD; Luft, B.J. MD; Anand, A.K. MD; Roque, C.T. MD; Alvarez, O. MD; Volkman, D.J. MD; and Dattwyler, R.J. MD. Lyme Neuroborreliosis: Central Nervous System Manifestations. Neurology. Vol. 39, No. 6, pp 753-759, June 1989.
(4) Mortality and Morbidity Reports. U.S. Center for Disease Control and Prevention. Atlanta, Georgia.
(5) Roizman, Bernard, editor. Infectious diseases in an age of change: the impact of human ecology and behavior on disease transmission. National Academy Press, Washington, D.C., 1995.
(6) Thomas, Claton L. ed. Taber's Cyclopedic Medical Dictionary. FA Davis Company. Philadelphia, Pennsylvania: 1993.
(7) Tortora, Gerald J., Berdell R. Funke, and Christine L.Case. Microbiology: An Introduction (5th edition). The Benjamin/Cummings Publishing Company, Inc. Redwood City, California, 1995.
(8) U.S. Bureau of the Census, Statistical Abstract of the United States: 1995 (115th Edition), Washington, D.C., 1995.
I have researched and answered these questions to the best of my ability. But I am human and make mistakes. If there is any part of my answer that you feel is incorrect, please let me know. The last thing I want is to disseminate false or incorrect information.