How is Lyme Disease Spread?
What are the symptoms of Lyme disease?
How is Lyme disease diagnosed?
Can Lyme disease be treated?
What precautions can be taken to reduce the chance of getting Lyme disease?
Is there a vaccine for Lyme disease?
Lyme disease is an infection caused by the bacterium Borrelia
burgdorferi that is transmitted by a tick bite. The disease can be difficult
to diagnose. It often starts with a large red rash at the site of the
tick bite, followed by flu-like symptoms and fatigue. Early in the course
of the disease, the symptoms often may go unnoticed or be mistaken for
the flu, and not all persons develop the same symptoms. To further complicate
matters, the symptoms of the disease mimic those of other diseases, so
even persons who complain of flu-like symptoms and fatigue can have any
number of conditions other than Lyme disease.
There are blood tests to check for antibodies to the bacterium that causes Lyme disease. The tests, however, are not useful if done soon after a tick bite, because it takes 2 to 5 weeks after being bitten by an infected tick for antibodies to develop. Even when an antibody (blood) test is done later, the result alone does not reliably predict the presence or absence of Lyme disease. (See "How is Lyme disease diagnosed?" below.) The Food and Drug Administration (FDA), which regulates diagnostic tests for Lyme disease, has cleared for commercial sale and distribution only blood tests for antibodies that may be present in Lyme disease. Tests for Lyme disease that use urine or other body fluids have not been cleared by FDA.
Lyme disease is spread by the bites of Ixodes ticks (the deer
tick, bear tick, western black-legged tick, or black-legged tick, depending
on the region of the country). These ticks are much smaller than the
common dog or cattle ticks. They can attach to any part of the body,
often to moist or hairy areas such as the groin, armpits, and scalp.
Campers, hikers, outdoor workers, and gardeners are at the greatest risk of exposure to infected ticks. Lyme disease is widely distributed in northern temperate regions of the world. In the United States, the highest incidence occurs in the Northeast, North Central states, and the West Coast (particularly in northern California).
The symptoms of early Lyme disease include:
Erythema migrans is a circular red patch that usually appears in 3 to 30 days after being bitten by an infected tick. The patch expands (to an average of 5 to 6 inches in diameter) and persists for 3 to 5 weeks. Sometimes many patches appear and vary in shape depending on their locations. The center of the patch may clear as the rash enlarges, giving a "bull's-eye" appearance. In some persons, the characteristic rash never forms or is not noticed, and not every rash that occurs at the site of a tick bite is due to Lyme disease. In some cases, the rash can be an allergic reaction to the tick saliva.
The symptoms of late Lyme disease may not appear until weeks, months, or even years after a tick bite and include:
Lyme disease can be difficult to diagnose, because its symptoms
mimic those of other diseases. For example, the fever, fatigue, and muscle
aches can be mistaken for influenza or infectious mononucleosis. Joint
pain can be mistaken for rheumatoid arthritis and neurologic signs for
multiple sclerosis. Conversely, other types of arthritis or neurologic
diseases can be misdiagnosed as Lyme disease.
To make a diagnosis of Lyme disease, the following should be considered:
If there are definite symptoms of Lyme disease, the doctor may prescribe antibiotics which are usually given by mouth. Antibiotics should not be given only because a person was bitten by a tick. Patients who are diagnosed and treated with antibiotics in the early stages of Lyme disease usually recover quickly and completely. Most patients treated in the later stages of Lyme disease also respond well to antibiotics. A few patients may have relapses and need additional antibiotic treatment. Permanent damage to the joints or the nervous system can develop in patients with chronic late Lyme disease. Usually these are patients not diagnosed in the early stages or their initial treatments were unsuccessful.
To decrease the chance of being bitten by a tick:
FDA recently licensed the first vaccine to aid in the prevention of Lyme disease. The new vaccine (trade-name Lymerix) is approved for use in persons 15 to 70 years of age who live or work in grassy or wooded areas where infected ticks are present. It is not currently available for persons under the age of 15 years.
Three doses of the vaccine, given over a period of one year, are needed. Although Lymerix may provide protection for a majority of people, it does not prevent all cases of Lyme disease. Studies by the manufacturer showed that after two doses of the vaccine in the first year, the protection rate against definite Lyme disease was 50 percent. In the second year after three doses, it was 78 percent. Since the vaccine is not 100 percent effective, continued preventive measures are still necessary for immunized individuals.