Lyme Disease

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Original Editors - Kevin Beale from Bellarmine University's Pathophysiology of Complex Patient Problems project.

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Definition/Description

Blacklegged/Deer Tick

Lyme disease is an infectious disorder caused by the spiral spirochete bacterium Borrelia burgdorferi which is transmitted to humans though the bite of infected ticks in the genus Ixodes (commonly referred to as “black-legged” or “deer” ticks). The ticks that carry the disease are extremely small, generally not larger than 1 to 2 mm (roughly the size of a pinhead, see photo at left).  Species of Borrelia capable of causing the disease occur regularly in the United States, Europe, Asia, and Australia.

[Photo courtesy of the Hardin Library for the Health Sciences, University of Iowa. Available at http://www.lib.uiowa.edu/HARDIN/MD/cdc/1669.html.]

Prevalence

As of 2008, Lyme Disease ranked as the most commonly reported vector-borne illness in the United States. Between 1992 and 2006, 248,074 cases were reported in the United States including the District of Columbia and the U.S. territories. The number of cases reported annually increased 101% from 9,908 cases in 1992 to 19,931 in 2006, with 93% of those cases occurring in 10 states in New England and the Upper Midwest (Connecticut, Delaware, Massachusetts, Maryland, New Jersey, New York, Pennsylvania, Rhode Island, and Wisconsin). 

File:CDC IncidenceMap 08.jpg

Reported Cases of Lyme Disease in the United States in 2008

Rates of incidence have continued to rise since 2006, with 27,444 cases reported in 2007 and 28,921 cases in 2008. As of 2008, the rate of incidence was 9.4 cases per 100,000. Children 5 to 14 years of age have the highest rate of incidence with an average of 8.6 cases per 100,000 compared to 3.0 cases per 100,000 for people 20 to 24 and 7.8 cases per 100,000 for ages 55 to 59. Most cases develop during the summer months of May and August when individuals are more likely to visit wooded areas for work or recreation.

[Chart courtesy of Lyme Disease Statistics, CDC Division of Vector-Borne Infectious Diseases. Available at http://www.cdc.gov/ncidod/dvbid/Lyme/ld_statistics.htm.]

Characteristics/Clinical Presentation

Clinical Manifestations
Lyme Disease is clinically similar to syphilis, a disorder which also can affect multiple organ systems and is also caused by a spirochete bacterium.  It also may occur in stages, progressing from a localized presentation (Stage 1) to a widespread infection involving neurolgical, musculoskeletal, and cardiac findings (Stage 2) to a final stage in which infection persists chronically resulting in long-term neurological symptoms, arthritis, and cognitive deficits (Stage 3).  Because the presentation of the disease is so variable, it can be exceedingly difficult for healthcare professionals to diagnose.  In addition, because it can so closely mimic other disorders such as multiple sclerosis, fibromyalgia, chronic fatigue syndrome, and Guillain-Barré syndrome, it is frequently called "The Great Imitator."   

The disease may present with one, some, or all of the symptoms listed below. Percentages for cases displaying each clinical finding below are derived from data collected by the CDC from 1992 to 2004. 

File:CDC Rash small.jpg

Erythema Migrans lesion

►Erythema migrans
88% of patients develop a red skin rash that enlarges over time. Many patients also report that their rash first presents with a bulls-eye pattern, with redness migrating outward concentrically from a dark central lesion bounded by a band of lighter color (see photo). This symptom generally occurs within a few days of infection, varies widely in severity or be absent altogether, and may or may not be accompanied by other symptoms. The variability of this symptom, combined with often mild symptoms of the early stages of the disease contributes to the difficulty in early diagnosing. 

[Photo courtesy of the CDC Division of Vector-borne Infectious Diseases. Available at http://www.cdc.gov/ncidod/dvbid/lyme/ld_lymediseaserashphotos.htm.]

►Flu-like symptoms
Fever, chills, fatigue, headache, and muscle or joint pain generally develop soon after infection (within several days) if they develop at all. In many cases, individuals who develop flu-like symptoms do not develop a rash. Thus, the presence of flu-like symptoms may represent the only clinical finding when a patient first presents.

►Neurological symptoms ,
About 15% of patients experience neurological signs and symptoms. The most common presentation is that of aseptic meningitis or encephalitis with symptoms including headache, neck stiffness, Bell’s (facial) palsy (8% of patients), radiculopathies (4% of patients), and mild to moderate cognitive changes including an inability to concentrate, forgetfulness, and changes in behavior or personality.

►Lyme Arthritis or general arthralgia
33% of patients develop Lyme-related arthritis, which causes swelling (usually unilaterally) in the large joints such as the knees.  Patients may also have myofascial or bone pain that moves over the course of hours or days.

►Cardiac symptoms
4 to 10% of patients present with cardiac signs and symptoms of varying severity such as tachycardia, bradycardia, arrhythmia, conduction block, or myocarditis.  Many patients with these findings may also report dizziness, shortness of air, and syncope.

Associated Co-morbidities

Babesia
Babesia microti is a parasite that enters the bloodstream along with Borrelia at the time of the tick bite and attacks and destroys the host’s red blood cells. It can be potentially life-threatening, especially in individuals who are elderly, immuno-compromised, do not have a spleen, or have other diseases involving the kidney or liver. If not treated, complications can include hemodynamic instability, anemia, thrombocytopenia, organ failure, or death. 

Chronic Fatigue Syndrome
Individuals who present with symptoms of significant fatigue and malaise consistent with a diagnosis of Chronic Fatigue Syndrome often test positive for Borrelia antibodies, suggesting a prior infection even in individuals with no previous clinical diagnosis of Lyme disease. In a double-blind study performed in Germany in 1999, researchers found that individuals who tested positive for Borrelia antibodies and had a history of tick bites were significantly more likely to report symptoms of fatigue and malaise than individuals who had a history of tick bites but tested negative for Borrelia antibodies.

Fibromyalgia Syndrome
Similar studies have found temporal links between Borrelia infection and the development of clinically diagnosable fibromyalgia, the etiology of which is generally multifactorial and can be triggered by environmental factors, trauma, stress, infection, and possibly vaccination.

Cardiac Dysfunction
Cardiac problems arising as a result of Lyme disease may occur in 4 to 10% of affected individuals. Potential problems include myocarditis, heart conduction block, and arrhythmia. Symptoms of cardiac involvement include bradycardia, tachycardia, irregular heart beat, dizziness, syncope, and shortness of air. 

Neurological disorders
Neurological and mental health co-morbidities develop in approximately 5% of Lyme disease patients, especially if the disease is not successfully treated initially.  Neurological sequelae include radiculopathy and paresthesias in the extremities. Associated mental health changes include mild cognitive impairments, mood disorders, depression, and anxiety.

Autism
Although controversy exists over whether or not autism is truly a co-morbidity of Lyme disease, recent research shows a correlation between the two. Chronic infectious diseases including the Borrelia organism that causes Lyme have been associated with other co-infections that may weaken the fetal or infant immune system, putting affected individuals at increased risk for developing autism spectrum disorders.

Medications

Acute cases of Lyme disease are initially treated with a 14 to 21 day course of oral antibiotics such as doxycycline or amoxicillin. If an affected individual presents with neurological impairments or a third degree heart block, IV antibiotics such as ceftriaxone are administered for 14 to 28 days. Lyme-related joint and muscle pain (Lyme arthritis) is also generally treated with oral antibiotics. If Lyme arthritis persists after a first course of antibiotics, an additional four week course of oral antibiotics is recommended. Arthritic symptoms that persist beyond both courses of antibiotic treatment are generally treated with antirheumatic and nonsteroidal anti-inflammatory (NSAID) medications.

Diagnostic Tests/Lab Tests/Lab Values

Lyme disease is generally diagnosed via a two-step process recommended by the CDC. First, the affected individual’s blood is tested for antibodies to Borrelia with either with an enzyme-linked immunoassay (ELISA) or indirect fluorescent antibody (IFA) tests. If either test is positive, the diagnosis is confirmed with a Western blot test. It should be noted that antibodies may not appear for 1 to 2 weeks after the initial infection. Therefore, blood tests may give negative results in the acute stage of the infection.

If hematology tests are negative but Lyme disease is still suspected or an individual is participating in Lyme-related research, a polymerase chain reaction (PCR) test may be administered to detect the DNA of the Borrelia bacterium.  In individuals with suspected Lyme arthritis, PCR is used to test the synovial fluid of affected joints.  If neurological symptoms are present, PCR is used to test the individual's cerebrospinal fluid.  PCR can also be used to test blood, urine, and skin. 

Causes

Lyme disease is caused by spirochete microorganisms in the family Borrelia (in the United States, the specific species involved is Borrelia burgdorferi) which are transmitted primarily by blacklegged or deer ticks. Deer ticks generally feed on the blood of deer, small birds, and mice, but are opportunistic and will also feed on the blood of other hosts such as cats, dogs, horses, and humans. Infected deer ticks transmit the bacteria to their host during the process of feeding. 

Risks for being bitten by a tick capable of transmitting Borrelia bacteria include spending time outdoors in wooded or grassy areas especially in the Northeast and Midwest (see Prevalence section above). Walking in wooded or grassy areas in shorts and/or short sleeves increases the risk because of the higher surface area of exposed skin. The risk of acquiring an infection also increases if a tick is allowed to remain attached to the body for more than 48 hours, allowing it to take in a full “blood meal.” If a tick is identified and removed prior to that time, the risk of infection is low.

Systemic Involvement

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Medical Management (current best evidence)

Because length and severity of symptoms can vary widely based on the stage at which Lyme disease is diagnosed, prevention is the key to avoiding infection. When individuals who live in tick-infested areas take appropriate preventive measures, the risk of infection is greatly reduced. The CDC has published a comprehensive guide to Lyme disease prevention and control, available here.

The FDA approved a vaccine for Lyme disease called LYMErix in 1998. However, the company who manufactured the vaccine ceased production in 2002 because of its high cost and lackluster sales.  At this time, there are no alternative vaccinations available for the disease. Though there is little evidence as to its efficacy, some physicians recommend a single dose of the oral antibiotic doxycycline to prevent infection when ticks are found to have been attached for 36 to 72 hours.

Current best evidence indicates the same treatments discussed in the Medications section above. Acute cases are initially treated with a 14 to 21 day course of oral antibiotics such as doxycycline or amoxicillin. If neurological impairments or a third degree heart block exists, IV antibiotics such as ceftriaxone are administered for 14 to 28 days. Lyme arthritis is also usually treated with oral antibiotics. If lyme-related muscle and joint pain persists after the first course of antibiotics, an additional four week course is recommended. Arthritic symptoms that persist beyond both courses of antibiotic treatment are treated with antirheumatic and nonsteroidal anti-inflammatories.

Physical Therapy Management (current best evidence)

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Alternative/Holistic Management (current best evidence)

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Differential Diagnosis

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Case Reports

• Early Lyme disease: solving the subtle clinical clues in an elderly patient [view article in Clinical Geriatrics]
• The Changing Face of Lyme Disease - Rural to Urban [view article in Hospital Physician]
• Unusual Presentation of Lyme Disease: Horner Syndrome with Negative Serology [view article in Journal of the American Board of Family Medicine]
• Late Diagnosis of Early Disseminated Lyme Disease: Perplexing Symptoms in a Gardener [view article in Journal of the American Board of Family Medicine]

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Resources

• CDC Division of Vector-Borne Infectious Diseases - http://www.cdc.gov/ncidod/dvbid/Lyme/
• American Lyme Disease Foundation - http://www.aldf.com
• Canadian Lyme Disease Foundation - http://www.canlyme.com

Recent Related Research (from Pubmed)

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References

see adding references tutorial.