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Lyme Disease - Causes, Symptoms and Treatment
Definition:
A multisystem disorder, Lyme disease is caused by the spirochete Borrelia burgdorferi, which is carried by thc minute tick Ixodes scapularis or another tick in the Ixodidae family. It often begins in the summer with the classic skin lesion called erythema chronicum migrans (ECM). Weeks or months later, cardiac or neurologic abnormalities sometimes develop, possibly followed by arthritis. Initially, Lyme disease was identified in a group of children in Lyme, Connecticut.
Now Lyme disease is known to occur primarily in three parts of the United States:
- In the northeast, from Massachusetts to Maryland.
- In the Midwest, in Wisconsin and Minnesota.
- In the west, in California and Oregon.
Although Lyme disease is endemic to these areas, cases have been reported in 43 states and 20 other countries, including Germany, Switzerland, France, and Australia.
Causes of Lyme Disease
Lyme disease occurs when a tick injects spirochete-laden saliva into the bloodstream or deposits fecal matter on the skin. After incubating for 3 to 32 days, the spirochetes migrate out to the skin, causing ECM. Then they disseminate to other skin sites or organs by the bloodstream or lymph system. The spirochetes' life cycle isn't completely clear; they may survive for years in the joints or they may trigger all inflammatory response in the host and then die.
Signs and Symptoms of Lyme Disease
Typically, Lyme disease has three stages.
Stage 1:
ECM heralds stage 1 with a red macule or papule, often at the site of a tick bite. This lesion usually feels hot and itchy and may grow to more than 20" (50 cm) in diameter. Within a few days, more lesions may erupt along with a malar rash, conjunctivitis, or diffuse urticaria. In 3 to 4 weeks, lesions are replaced by small red bolches,which persist for several more weeks. Malaise and fatigue are constant, but other findings are intermittent: headache, fever, chills, and regional lymph adenopathy. Less common effects are meningeal irritation, mild encephalopathy, migrating musculoskeletal pain, and hepatitis. A persistent sore throat and dry cough may appear several days before ECM.
Stage 2:
Weeks to months later, the second stage begins with neurologic abnormalitiesfluctuating meningoencephalitis with peripheral and cranial neuropathy - that usually resolve after days or months. Facial palsy is especially noticeable. Cardiac abnormalities, such as a brief, fluctuating atrioventricular heart block, may also develop.
Stage 3:
Characterized by arthritis, stage 3 begins weeks or years later. Migrating musculoskeletal pain leads to frank arthritis with marked swelling, especially in the large joints. Recurrent attacks may precede chronic arthritis with severe cartilage and bone erosion.
Diagnosis for Lyme Disease
Because isolation of B. burgdorferi is unusual in humans and because indirect immunofluorescent antibody tests are marginally sensitive, diagnosis often rests on the characteristic ECM lesion and related clinical findings, especially in endemic areas. Mild anemia and an elevated erythrocyte sedimentation rate, leukocyte count, serum immunoglobulin M level, and aspartate aminotransferase level support the diagnosis. The National Institute of Allergy and Infectious Diseases (NIAID) is researching a more sensitive diagnostic test for Lyme disease. Differential diagnoses are chronic fatigue syndrome and fibromyalgia; however, these can also develop in association with, or soon after, contracting Lyme disease.
Treatment for Lyme Disease
A 28-day course of oral tetracycline is the treatment of choice for adults. Penicillin and erythromycin are alternates. Oral penicillin is usually prescribed for children. When given during the late stages, high-dose ceftriaxone I.V. may be a successful treatment. Neurological abnormalities are best treated with I.V. ceftriaxone or I.V. penicillin.
Special Considerations and Prevention Tips for Lyme Disease
- Antibiotic therapy should be started early to minimize later complications.
- A vaccine (Lymerix) is available in the U.S. to prevent Lyme disease. For maximal effectiveness, it's given as a series of 3 injections. Lymerix is not likely to be highly effective in Europe and Asia because of the diversity of genospecies that cause Lyme disease in these countries.
- Take a detailed patient history, asking about travel to endemic areas and exposure to ticks.
- Check for drug allergies, and administer antibiotics carefully.
- For a patient with arthritis, help with range-of-motion and strengthening exercises, but avoid overexertion.
- Assess the patient's neurologic function and level of consciousness frequently. Watch for signs of increased intracranial pressure and cranial nerve involvement, such as ptosis, strabismus, and diplopia.
- Check for cardiac abnormalities, such as dysrhythmias and heart block.
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