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neurology channel |
What is Lyme disease?
Lyme disease (LD) is an infection caused by Borrelia burgdorferi, a
type
of bacterium called a spirochete (pronounced spy-ro-keet) that is
carried
by deer ticks. An infected tick can transmit the spirochete to the
humans
and animals it bites. Untreated, the bacterium travels through the
bloodstream,
establishes itself in various body tissues, and can cause a number of
symptoms,
some of which are severe.
LD manifests itself as a multisystem inflammatory disease that affects the skin in its early, localized stage, and spreads to the joints, nervous system and, to a lesser extent, other organ systems in its later, disseminated stages. If diagnosed and treated early with antibiotics, LD is almost always readily cured. Generally, LD in its later stages can also be treated effectively, but because the rate of disease progression and individual response to treatment varies from one patient to the next, some patients may have symptoms that linger for months or even years following treatment. In rare instances, LD causes permanent damage.
Although LD is now the most common arthropod-borne illness in the U.S. (more than 100,000 cases have been reported to the Centers for Disease Control and Prevention [CDC] since 1982), its diagnosis and treatment can be challenging for clinicians due to its diverse manifestations and the unreliability of currently available serological (blood) tests.
The prevalence of LD in the northeast is due to the presence of large numbers of the deer tick's preferred hosts - white-footed mice and deer - and their proximity to humans. White-footed mice serve as the principal "reservoirs of infection" on which many nymphal (juvenile) ticks feed and become infected with the LD spirochete. An infected tick can then transmit its store of spirochetes to its next host (e.g., an unsuspecting human).
The LD spirochete, Borrelia burgdorferi, infects other species of ticks but is known to be transmitted to humans and other animals only by the deer tick (also known as the black-legged tick) and the related Western black-legged tick. Studies have shown that an infected tick normally cannot begin transmitting the spirochete until it has been attached to its host about 36-48 hours; the best line of defense against LD, therefore, is to examine yourself at least once daily and remove any ticks before they become engorged (swollen) with blood.
Generally, if you discover a deer tick attached to your skin that has not yet become engorged, it has not been there long enough to transmit the LD spirochete. Nevertheless, it is advisable to be alert in case any symptoms do appear; a red rash (especially surrounding the tick bite), flu-like symptoms, or joint pains in the first month following any deer tick bite could signal the onset of LD.
Manifestations of what we now call Lyme disease were first reported in medical literature in Europe in 1883. Over the years, various clinical signs of this illness have been noted as separate medical conditions: acrodermatitis, chronica atrophicans (ACA), lymphadenosis benigna cutis (LABC), erythema migrans (EM), and lymphocytic meningradiculitis (Bannwarth's syndrome). However, these diverse manifestations were not recognized as indicators of a single infectious illness until 1975, when LD was described following an outbreak of apparent juvenile arthritis, preceded by a rash, among residents of Lyme, Connecticut.
Where is Lyme disease prevalent?
LD is spreading slowly along and inland from the upper east coast, as
well
as in the upper midwest and the northern California and Oregon coast.
The
mode of spread is not entirely clear and is probably due to a number of
factors
such as bird migration, mobility of deer and other large mammals, and
infected
ticks dropping off of pets as people travel around the country.
In order to assess LD risk you should know whether infected deer ticks are active in your area or in places you may visit. The population density and percentage of infected ticks that may transmit LD vary markedly from one region of the country to another. There is even great variation from county to county within a state and from area to area within a county. For example, less than 5% of adult ticks south of Maryland are infected with B. burgdorferi, while up to 50% are infected in hyperendemic areas (areas with a high tick infection rate) of the northeast. The tick infection rate in Pacific coastal states is between 2% and 4%.
For a detailed look at the geographic prevalence of LD throughout the United States, please see the American Lyme Disease Foundation Inc.'s color-coded distribution maps of reported cases and rates of disease incidence in 1997 (the latest available figures) and the accompanying table of actual reported cases and incidence rate per state.
Symptoms
The early symptoms of LD can be mild and easily overlooked. People who
are
aware of the risk of LD in their communities and who don't ignore the
sometimes
subtle early symptoms are most likely to seek medical attention and
treatment
early enough to be assured of a full recovery.
The first symptom is usually an expanding rash (called erythema migrans, or EM, in medical terms) which is thought to occur in 80% to 90% of all LD cases. An EM rash generally has the following characteristics:
• Usually (but not always) radiates from the site of the tickbite
• Appears either as a solid red expanding rash or blotch, OR a central
spot
surrounded by clear skin that is in turn ringed by an expanding red
rash
(looks like a bull's-eye)
• Appears an average of 1 to 2 weeks (range = 3 to 30 days) after
disease
transmission
• Has an average diameter of 5 to 6 inches (range = 2 inches to 2 feet)
• Persists for about 3 to 5 weeks
• May or may not be warm to the touch
• Is usually not painful or itchy
EM rashes appearing on brown-skinned or sun-tanned patients may be more difficult to identify because of decreased contrast between normal skin tones and the red rash. A dark, bruise-like appearance is more common on dark-skinned patients.
Ticks will attach anywhere on the body, but prefer body creases such as the armpit, groin, back of the knee, and nape of the neck; rashes will therefore often appear in (but are not restricted to) these areas. Please note that multiple rashes may, in some cases, appear elsewhere on the body some time after the initial rash, or, in a few cases, in the absence of an initial rash.
Around the time the rash appears, other symptoms such as joint pains, chills, fever, and fatigue are common, but they may not seem serious enough to require medical attention. These symptoms may be brief, only to recur as a broader spectrum of symptoms as the disease progresses.
As the LD spirochete continues disseminating through the body, a number of other symptoms including severe fatigue, a stiff, aching neck, and peripheral nervous system (PNS) involvement such as tingling or numbness in the extremities or facial palsy (paralysis) can occur.
The more severe, potentially debilitating symptoms of later-stage LD may occur weeks, months, or, in a few cases, years after a tick bite. These can include severe headaches, painful arthritis and swelling of joints, cardiac abnormalities, and central nervous system (CNS) involvement leading to cognitive (mental) disorders.
The following is a checklist of common symptoms seen in various stages of LD:
Localized Early (Acute) Stage:
• Solid red or bull's-eye rash, usually at site of bite
• Swelling of lymph glands near tick bite
• Generalized achiness
• Headache
Early Disseminated Stage:
• Two or more rashes not at site of bite
• Migrating pains in joints/tendons
• Headache
• Stiff, aching neck
• Facial palsy (facial paralysis similar to Bell's palsy)
• Tingling or numbness in extremities
• Multiple enlarged lymph glands
• Abnormal pulse
• Sore throat
• Changes in vision
• Fever of 100 to 102 F
• Severe fatigue
Late Stage:
• Arthritis (pain/swelling) of one or two large joints
• Disabling neurological disorders (disorientation; confusion;
dizziness;
short-term memory loss; inability to concentrate, finish sentences or
follow conversations; mental "fog")
• Numbness in arms/hands or legs/feet
Diagnosis
If you think you have LD symptoms you should see your physician
immediately. The EM rash, which may occur in up to 90% of the reported
cases, is a specific feature of LD, and treatment should begin
immediately.
Even in the absence of an EM rash, diagnosis of early LD should be made solely on the basis of symptoms and evidence of a tick bite, not blood tests, which can often give false results if performed in the first month after initial infection (later on, the tests are considered more reliable). If you live in an endemic area, have symptoms consistent with early LD and suspect recent exposure to a tick, present your suspicion to your doctor so that he or she may make a more informed diagnosis.
If early symptoms are undetected or ignored, you may develop more severe symptoms weeks, months or perhaps years after you were infected. In this case, the CDC recommends using the ELISA and Western-blot blood tests to determine whether you are infected. These tests, as noted above, are considered more reliable and accurate when performed at least a month after initial infection, although no test is 100% accurate.
If you have neurological symptoms or swollen joints your doctor may, in addition, recommend a PCR (Polymerase Chain Reaction) test via a spinal tap or withdrawal of synovial fluid from an affected joint. This test amplifies the DNA of the spirochete and will usually indicate its presence.
Because the role of the recommended ELISA and Western blot tests in Lyme disease diagnosis is often poorly understood by both physicians and patients, the FDA has issued the following bulletin (slightly edited for the lay audience) clarifying common misperceptions:
Lyme disease testing: potential for misdiagnosis
There is widespread concern about the potential for misdiagnosis of
Lyme
disease based on the results of commonly used serological tests such as
the
ELISA, IFA and Western blot, all of which detect antibodies to the
causative
bacteria, B. burgdorferi. It is important that physicians ordering
these
tests understand that a positive test result does not necessarily
indicate
current infection with B. burgdorferi, and a patient with active Lyme
disease
may have a negative test result. (1-5)
The tests should be used only to support a clinical (symptom-based) diagnosis of Lyme disease and should never be the primary basis for making diagnostic or treatment decisions. Diagnosis should be based on a patient's history, including symptoms, exposure to ticks or a tick bite, high-risk activities prior to onset of symptoms, and the time of year symptoms began.
Assays for Lyme disease antibodies can provide evidence of previous or current infection, but to improve test reliability, the FDA supports the Centers for Disease Control and Prevention (CDC) recommendation for two-step testing and interpretation of results (1):
The first step is to perform an assay that detects either total or class-specific antibodies (IgM-type antibodies or IgG-type antibodies) by using the ELISA titer. Levels of IgM (early) antibodies usually peak 3 to 6 weeks after infection. IgG antibodies appear somewhat later, becoming detectable several weeks after infection and continuing to develop for several months. The IgG antibodies generally persist for years.
Clinicians should note that:
• A negative result indicates only that there was no serologic evidence
of
infection with B. burgdorferi. It should not be used as the basis for
excluding
Lyme disease as the cause of illness, especially if the blood was
collected
within 2 weeks of the onset of
symptoms.
• A positive or equivocal result on the ELISA is only presumptive evidence of the presence of Lyme disease antibodies. It should always be followed by second-step testing and should not be reported until the second step testing is completed.
The second step is to perform a Western blot (immunoblot) assay, a more specific assay than that used for the first step:
• A negative result indicates that no reliable serologic evidence of B. burgdorferi infection was present. It should not be used as the sole basis for excluding Lyme disease as the cause of illness. If Lyme disease is suspected, a second specimen collected 2 to 4 weeks after the first specimen should be tested. If retesting, begin again with the ELISA; if this result is positive or equivocal, continue with the Western blot.
• A positive result provides serologic evidence of past or current infection with B. burgdorferi. Because the presence of even specific antibodies to B. burgdorferi does not always indicate current infection, a positive result can support, but not establish, a clinical diagnosis of Lyme disease.
Even using the two-step approach, the sensitivity and specificity of
the
combined test results are inadequate. Because assays for Lyme disease
antibodies
should be used only for supporting a clinical diagnosis of Lyme disease
and
not for "screening" asymptomatic individuals, the result of the
first-step
assay is best described as "initial" rather than "screening." Likewise,
the
second-step western blot assay is best described as "supplemental"
rather
than "confirmatory," because of the low specificity for detecting IgM
antibodies
to Lyme disease. Thus, a positive IgM result alone is not adequate for
supporting
a diagnosis of Lyme disease in persons with illness of greater than
one-month duration.
Several factors contribute to the limitations of using ELISA, IFA or Western blot tests for supporting a diagnosis of Lyme disease. The stage of disease in which the specimen was taken is critical. Many patients with active or recent infections do not have detectable Lyme disease antibodies in a single specimen. This happens because such antibodies are often produced after manifestations of early infection or because detectable antibody levels may diminish or never develop in patients treated with antibiotics. Furthermore, a positive test result can be true evidence of previous infection with B. burgdorferi and unrelated to a current illness. Assays for Lyme disease antibodies may yield false-positive results, because antibodies to B. burgdorferi may cross-react with antigens associated with autoimmune diseases or from infection with other spirochetes, rickettsia, ehrlichia, or other bacteria such as Helicobacter pylori. (6,7)
In summary, serologic testing is not useful early in the course of Lyme disease, because of the low sensitivity of tests in early disease. Serologic testing may be more useful in later disease at which time sensitivity and specificity of the test is improved.
References
1. Center for Disease Control and Prevention. Recommendations for test
performance
and interpretation from the second national conference on serologic
diagnosis
of Lyme
Disease. MMWR 1995; 44:590-591.
2. Association of State and Territorial Public Health Laboratory
Directors and the Centers for Disease Control and Prevention.
Recommendations. In: Proceedings
of the
Second National Conference on Serologic Diagnosis of Lyme Disease
(Dearborn, Michigan). Washington, DC: Association of State and
Territorial Public Health
Laboratory
Directors 1995; 1-5.
3. Craven RB, Quan TJ, Bailey RE, Dattwyler RJ, Ryan RW, Sigal LH,
Steere AC, Sullivan B, Johnson BJB, Dennis DT, Gubler DJ. Improved
serodiagnostic testing for
Lyme disease; results of a multi center serologic evaluation. Emerging
Infect
Diseases 1996; 136-140.
4. Bakken LL, Callister SM, Wand PJ, Schell RF. Interlaboratory
comparison of test results for detection of Lyme disease by 516
participants in the Wisconsin
State
Laboratory of Hygiene/College of American Pathologists proficiency
testing
program. J Clin Microbiol 1997; 35:537-543.
5. Johnson RC, Johnson BJB. Lyme disease: serodiagnosis of Borrelia
burgdorferi
sensu lato infection. In: Rose NR, Macario EC, Fahey JL, Freidman H,
Penn
GM, eds.
Manual of Clinical Laboratory Immunology, 5th ed. Washington, DC:
American Society for Microbiology, 1997: 526-533.
6. Magnarelli LA, Miller JN, Anderson JF, Riviere GR.
Cross-reactivity of non-specific treponemal antibody in serologic tests
for Lyme disease. J
Clin Microbiol
1990;28:1276-1279.
7. Schwan TG, Burgdorfer W, Rosa PA. Borrelia. In: Murray PR, Baron
EJ,
Pfaller MA, Tenover FC, Yolken RH, eds. Manual of Clinical
Microbiology, 6th
ed. Washington,
DC: American Society for Microbiology, 1995:626-635.
Treatment
Doxycycline, amoxicillin and ceftin are the three oral antibiotics most highly recommended for treatment of all but a few symptoms of LD. A recent study of Lyme arthritis in the New England Journal of Medicine indicates that a four-week course of oral doxycycline is just as effective in treating late LD, and much less expensive, than a similar course of intravenous Ceftriaxone (Rocephin) unless neurological or severe cardiac abnormalities are present. If these symptoms are present, the study recommends immediate intravenous (IV) treatment.
Treatment of late-Lyme patients is, unfortunately, an inexact science. Often, LD in its later stages can be treated effectively, but individual variation in the rate of disease progression and response to treatment may, in some cases, render standard antibiotic treatment regimens ineffective. In a small percentage of late-Lyme patients, the disease becomes a treatment-resistant chronic condition with symptoms persisting for many months or even years. Conversely, a significant percentage of late-Lyme patients have reported a slow improvement in and ultimate resolution of their persisting symptoms months or even years following oral or IV treatment that apparently eliminated the infection.
Although treatment approaches for patients with late-stage LD have become a matter of considerable debate, many physicians and the CDC recognize that, in some cases, multiple courses of either oral or IV (depending on the symptoms presented) antibiotic treatment may be indicated. However, long-term IV treatment courses (longer than the recommended 4-6 weeks) are not usually advised due to possible adverse side effects, including auto-immune deficiencies. While there is some speculation that long-term courses may be more effective than the recommended 4-6 weeks in certain cases, there is currently no scientific evidence to support this assertion.
Prevention & Control
Deer ticks prefer to hide in shady, moist ground litter, but can often
be
found above the ground clinging to tall grass, brush, shrubs and low
tree
branches. They also inhabit lawns and gardens, especially at the edges
of
woodlands and around old stone walls where deer and white-footed mice,
the
ticks' preferred hosts, thrive. Within the endemic range of B.
burgdorferi (the spirochete that infects the deer tick and causes LD),
no natural, vegetated
area can be considered completely free of infected ticks.
Deer ticks cannot jump or fly, and will not drop from an above-ground perch onto a passing animal. Potential hosts (which include all wild birds and mammals, domestic animals, and humans) acquire ticks only by direct contact with them. Once a tick gains access to human skin it generally climbs upward until it reaches a more protected area, often the back of the knee, groin, navel, armpit, ears, or nape of the neck. It then begins the process of inserting its mouthparts into the skin until it reaches the blood supply.
In tick-infested areas, the best precaution against LD is to avoid contact with soil, leaf litter and vegetation as much as possible. However, if you garden, hike, camp, hunt, work outdoors or otherwise spend time in the woods, brushy areas or overgrown fields, you should use the following personal precautions to avoid exposure to ticks:
• Wear light-colored clothing with a tight weave to spot ticks more
easily and
prevent contact with the skin
• Always wear enclosed shoes or boots
• Wear long pants tucked into socks, long-sleeved shirts tucked into
pants
(however, be aware that ticks search for exposed skin and may climb to
the
head and neck area if not intercepted first; spot-check clothes
frequently)
• Spray clothes with insect repellent containing either DEET or
Permethrin
(only DEET can be used on exposed skin, but never in high
concentrations;
follow the manufacturer's directions)
• Keep long hair pulled back
• When gardening, pruning shrubs, or otherwise handling soil and
vegetation,
wear light-colored gloves, spot-checking them for ticks frequently.
• Avoid sitting on the ground or on open stone walls (which attract
small
mammals)
• Stay on cleared, well-travelled trails whenever possible
• During any outing, spot-check yourself and others frequently for
ticks on
clothes and skin; if you find one, there may be others - check
thoroughly
• Remove clothes after leaving tick-infested areas and, if possible,
wash and
dry them to eliminate any unseen ticks
• Shower and shampoo
• Check yourself, your children and any pets from head to toe for ticks
each
night before going to bed (nymphal deer ticks are the size of poppy
seeds;
adult deer ticks are the size of sesame seeds)
Any contact with vegetation, whether bushwhacking through dense brush or simply playing in the yard, can result in exposure to ticks, so careful daily self-inspection is necessary whenever you engage in outdoor activities and the temperature exceeds 40 degrees F (the temperature above which deer ticks are active). Frequent tick checks should include a systematic, whole-body examination each night before going to bed. Performed consistently, this ritual is perhaps the single most effective current method for prevention of Lyme disease. (As discussed above in What is Lyme Disease?, you can greatly reduce your chances of contracting LD if you remove a tick within 36 hours after it attaches to your skin.)
If you DO find a tick attached to your skin, use the following method to remove it:
(1) Using a pair of fine-tipped tweezers, grasp the tick by the head
or
mouthparts right where they enter the skin. DO NOT grasp the tick by
the
body.
(2) Without jerking, pull firmly and steadily directly outward. DO NOT
twist
the tick out or apply petroleum jelly, a hot match, alcohol or
any
other irritant to the tick in an attempt to get it to back out. These
methods
can backfire and even increase the chances of the tick transmitting the
disease.
(3) Place the tick in a vial or jar of alcohol to kill it.
(4) Clean the bite wound with disinfectant.
Keep in mind that certain types of fine-pointed tweezers, especially those that are etched, or rasped, at the tips, may not be effective in removing nymphal deer ticks. Choose unrasped fine-pointed tweezers whose tips align tightly when pressed firmly together.
Prevention is not limited to personal precautions. Those who enjoy spending time in their yards can reduce the tick population in the vicinity of the home by:
• keeping lawns mowed and edges trimmed
• clearing brush, leaf litter and tall grass around houses and at the
edges of
gardens and open stone walls
• stacking woodpiles neatly in a dry location and preferably off the
ground
• clearing all leaf litter (including the remains of perennials) out of
the
garden
in the fall
• keeping the ground under bird feeders clean so as not to attract
small
mammals
• having a licensed professional spray the residential environment (only the areas frequented by humans) with an insecticide in late May (to control nymphs) and optionally in September (to control adults)
Vaccines for Lyme disease have been tested in clinical trials and one (LYMErix) has been approved by the Food and Drug Administration (FDA). For further information and updates on the new vaccine, please see the Late breaking news page on the American Lyme Disease Foundation, Inc. website
This information was developed by the American Lyme Disease Foundation, Inc. and is herewith used with permission.
American Lyme Disease Foundation, Inc. Lyme Disease? Available at: http://www.aldf.com/templates/Lyme.cfm. Accessed October 20, 1999.
The information in this document is for general educational purposes only. It is not intended to substitute for personalized professional advice. Although the information was obtained from sources believed to be reliable, Arbor Publishing Corp, its representatives, and the providers of the information do not guarantee its accuracy and disclaim responsibility for adverse consequences resulting from its use. For further information, consult a physician and the organization referred to herein.