Although first seen almost 40 years ago, Lyme disease continues to present diagnostic challenges for patients and their physicians.
In 1975, concerned by varied joint, heart and nervous system symptoms in their children, mothers in Lyme, Conn., contacted the U.S. Centers for Disease Control and Prevention for assistance. Subsequent studies identified a previously unknown bacterium, Borrelia burgdorferi (Bb), as the cause of the disease. The organism is transmitted by the bite of the deer tick, and the illness was named for the town around which the disease was first detected.
The disease is concentrated in the upper Atlantic seaboard and Minnesota and Wisconsin so, officially, Lyme disease is rare in our region; however most cases are not reported because of diagnostic uncertainty.
Children and middle-aged adults are most commonly affected. Lab tests depend upon the detection of antibodies to Bb in the blood. These antibodies are often absent during acute illness.
Confirmed cases number 30,000 annually in our country, but up to 300,000 cases may actually occur in the U.S. each year. The disease has been detected in Western Europe and parts of Asia, where it is transmitted by other tick species.
Deer and small mammals such as mice and chipmunks serve as reservoirs for Bb. A deer tick bites an infected animal and subsequently transmits the organism by biting a human. Because the tick is quite small, the size of a poppy seed, it may easily be overlooked. If undisturbed, the infecting tick will detach itself after several days. Up to half of confirmed cases will not recall a preceding tick bite.
Several days to a month after a bite from an infected tick, a small reddish bump or raised rash usually develops at the site. The rash usually is painless and does not itch. This may slowly expand, sometimes resembling a bullseye: a central rash, surrounded by a ring of normal skin, then a circular rash. Rash also may develop on other parts of the body. Headache, muscle aches and mild fever may accompany the rash. Left untreated, the rash will fade over days or weeks. In some instances, a rash either does not occur or is too small to be noted.
Blood tests during the acute phase of illness are often nondiagnostic. Outpatient antibiotic treatment is given on the basis of a history of tick bite followed by a characteristic rash. The treatment usually takes care of the infection.
Left untreated, however, Bb may go underground for weeks to months. Rash may accompany resurgent symptoms that include muscle aches, fever, fatigue and swollen lymph glands. Disturbances in heart rhythm may occur. Weight-bearing joints may become swollen and tender.
Less commonly, temporary paralysis involving one or more nerves may develop. These symptoms may include one-sided facial paralysis or abnormal eye movements. Meningitis -- inflammation of the membranes surrounding the brain and spinal cord -- occurs rarely. Sustained oral or intravenous antibiotic therapy usually cures infections at this stage.
Months to years later, arthritis with fluid accumulation may occur in untreated patients. Knees are most commonly involved. Persistent nervous system symptoms may develop, including chronic headache, impaired learning and memory. Fatigue, sometimes disabling in its intensity, may persist. Intensive antibiotic therapy is applied at this stage. Symptoms, however, may recur even after treatment.
Careful inspection of skin after walks or camping in grasslands and woodlands is crucial for detection of ticks. Clothing on such expeditions should be promptly washed because ticks may linger for days in folds. When detected, ticks should be carefully removed with tweezers. Rash, joint pain and swelling, and nervous system changes occurring after tick bites, even if months after the event, should immediately raise the possibility of Lyme disease so prompt lab testing and, if indicated, antibiotic therapy, can be launched.
Twice in recent months, young female relatives in South Carolina and New York State have developed painful, fluid-filled knees. Each had a history of a single tick bite months earlier with no rash. Lab studies suggested Lyme disease. Antibiotic therapy cured the problem in each instance.
The bottom line is: Lyme disease is not rare.
Contact Clif Cleaveland at firstname.lastname@example.org.