Basics of Lyme Disease

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Lyme disease has been in the news recently as Minnesota recorded a fourfold increase in cases from 1998 to 2008 and Utah reported an outbreak of cases. Utah is not a state commonly thought of in terms of Lyme disease.

Lyme disease is caused by the spirochete Borrelia burgdorferi, a corkscrew-shaped bacterium. It is transmitted with the bite of certain Ixodes ticks, particularly the blacklegged tick, I. scapularis, in the northeastern and north-central United States and the western blacklegged tick, Ixodes pacificus, on the Pacific Coast. Other Ixodes ticks spread the disease in Europe and Asia. More commonly these ticks are known as deer ticks or bear ticks.

The Centers for Disease Control and Prevention (CDC) reports that between the years of 1990 and 2008, the top seven ranking states in total Lyme disease cases were New York, Pennsylvania, Connecticut, New Jersey, Massachusetts, Wisconsin and Maryland. Even so, the disease has been reported from 49 states, as well as parts of Canada, and across Europe and Asia.

Lyme disease was first recognized as a distinct clinical entity in a group of arthritis patients from the area of Lyme, Connecticut in 1975. Dr. Willy Burgdorfer and co-workers discovered spirochetes in the mid-gut of some I. scapularis ticks from Long Island, New York in 1981.

Nationally, human case reports have been running around 20,000 to 24,000 cases annually. It is felt that Lyme disease is underreported.

Lyme disease affects all age groups, but the greatest incidence of disease has been in children under 14 and adults over 40 years of age. In most cases, Lyme disease symptom onset occurs during the summer months when the nymphal stage of the blacklegged tick is active.

Lyme disease bacteria can infect several parts of the body, producing different symptoms at different times. These may include diverse cutaneous, arthritic, neurologic, cardiac, and occasional ocular manifestations.

The first sign of infection is usually a circular rash called erythema migrans or EM. This rash occurs in approximately 70-80% of infected persons and begins at the site of a tick bite after a delay of 3-30 days. A distinctive feature of the rash is that it gradually expands over a period of several days, reaching up to 12 inches (30 cm) across. The center of the rash may clear as it enlarges, resulting in a bull's-eye appearance. The rash may be warm but is not usually painful.

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Patients also experience symptoms of fatigue, chills, fever, headache, and muscle and joint aches, and swollen lymph nodes. In some cases, these may be the only symptoms of infection.

Untreated, the infection may spread to other parts of the body within a few days to weeks, producing an array of discrete symptoms. These include loss of muscle tone on one or both sides of the face (called facial or "Bell's palsy), severe headaches and neck stiffness due to meningitis, shooting pains that may interfere with sleep, heart palpitations and dizziness due to changes in heartbeat, and pain that moves from joint to joint. Many of these symptoms will resolve, even without treatment.

If left untreated, approximately 60% of patients will begin to have intermittent bouts of arthritis, with severe joint pain and swelling after several months. Large joints are most often affected, particularly the knees. In addition, up to 5% of untreated patients may develop chronic neurological complaints months to years after infection. These include shooting pains, numbness or tingling in the hands or feet, and problems with concentration and short term memory.

Most cases of Lyme disease can be cured with antibiotics, especially if treatment is begun early in the course of illness. However, a small percentage of patients with Lyme disease have symptoms that last months to years after treatment with antibiotics. These symptoms can include muscle and joint pains, arthritis, cognitive defects, sleep disturbance, or fatigue. The cause of these symptoms is not known. There is some evidence that they result from an autoimmune response, in which a person's immune system continues to respond even after the infection has been cleared.

According to CDC it takes 36-48 hrs for transmission of B.burgdorferi or B. microti to occur from an attached tick and not all ticks are infected. Therefore, a tick bite does not necessarily mean a person will get infected. Prompt removal of the attached tick will reduce the chance of infection.

The "preventive" steps to take are to either avoided the tick-invested area or used a DEET or permethrin-based tick repellent and then doing a body check for ticks that same evening. Wearing light-colored clothing can help identify ticks that may be hitchhiking on your person.

Not all patients with Lyme disease will have all symptoms, and many of the symptoms can occur with other diseases as well. If you believe you may have Lyme disease, it is important that you consult your health care provider for proper diagnosis.

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Sources
Center for Disease Control and Prevention

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