What is Lyme disease?

SOURCE:  California Lyme Disease Association – www.lymedisease.org

Lyme disease is an infection caused by a spirochete (say “SPY-ROH-KEET”) that humans can get from the bite of an infected deer tick. The spirochete’s scientific name is Borrelia burgdorferi. Lyme disease is called “The Great Imitator” because its symptoms mimic many other diseases. It can affect any organ of the body, including the brain and nervous system, muscles and joints, and the heart.

How do people get Lyme disease?

People usually get Lyme disease from ticks infected with Lyme spirochetes. Most human cases are caused by the nymphal, or immature, form of the tick. Nymphs are about the size of a poppy seed. Because their bite is painless, many people do not realize they have been bitten.

Ticks may remain attached for several days while they feed. The longer they remain attached, the greater the risk that they will pass the Lyme bacteria into your bloodstream, where they will start spreading throughout your body.

If pregnant women are infected, they sometimes pass Lyme disease to their unborn children. Some doctors believe other types of human-to-human transmission are possible but little is known for certain.

Where is Lyme disease found?

Lyme disease has been found on every continent except Antarctica. It is found all across the United States, with a particularly high incidence in the east, midwest, and west coast. It seems to be spreading.

Not all ticks are infected. Within endemic areas, there is considerable variation locally, depending on type of habitat, presence of wildlife, and other factors. In the south, a Lyme-like disease is called STARI (Southern Rash-Associated Tick Illness).

Early Lyme

Early in the infection, many people experience a flu-like illness that may clear up without treatment. Some people get a rash around the site of the tick bite. Most of the time the rash is an ordinary red area, however if it is a bull’s-eye shape with a darker edge, it is a definite sign of Lyme disease and needs immediate treatment. Unfortunately this distinctive rash is uncommon.

The Lyme rash starts a few days or even several weeks after the bite and then expands over a period of days to several inches across, perhaps with a central clearing. Untreated, it can last for weeks before fading, or it may fade and recur. The rash may have an irregular shape, blisters or a scabby appearance. Some rashes have a bruise-like appearance. Lyme rashes can mimic spider bite, ringworm, or cellulitis. Multiple, so-called “satellite” rashes may appear on different parts of the body. If you develop a rash, take a photo of it and see a doctor as soon as possible.

Your doctor may want you to have a blood test to confirm that the rash is actually a Lyme rash. People with early Lyme disease do not develop the antibodies necessary for the diagnostic tests for several weeks, and, early testing can give false negative results because of this. Although all medical treatment has some risk, treatment with antibiotics is relatively safe. Waiting for test results gives the spirochetes additional time to invade your body. Your doctor should explain the risks so you can make an informed choice.

Chronic Lyme

If Lyme disease is not diagnosed and treated early, the Lyme spirochetes can spread and may go into hiding in your body. Weeks, months or even years later you may have problems with your brain and nervous system, muscles and joints, heart and circulation, digestion, reproductive system, and skin. Symptoms may disappear even without treatment and different symptoms may appear at different times.

Diagnosis is clinical and is based primarily on recognition of the typical symptoms of Lyme disease in a person who lives in a high-risk area. Doctors like to have hard evidence to back up their opinions, but testing is not an exact science: the tests for Lyme disease may sometimes be negative in cases where disease is actually present, and false positive tests, though less common, are also possible. Therefore, experienced doctors recommend that Lyme disease be diagnosed clinically, meaning they base the diagnosis on an evaluation of your risk and your symptoms.

People with chronic Lyme disease may be misdiagnosed with more familiar conditions with symptoms that mimic Lyme disease.

Lyme Mimics

Since scientists have not figured out the cause of these diseases and treatment does not call for antibiotics, the underlying Lyme infection is allowed to progress unchecked.

Diagnostic tests

Some doctors consider a bull’s-eye rash diagnostic and don’t require further tests. Others, however, require laboratory confirmation before treatment.

Culture is the “gold standard” test for identifying bacteria. A sample of the organism is taken from the patient is allowed to grow in a medium and then identified. Culture is accepted as proof of infection. While culture is used to diagnose many infections, it is not practical for Lyme because the bacteria grow too slowly. There are no commercially available culture tests for Lyme.

Antibody tests

The most common tests measure the patient’s antibody response to infection. When your body is invaded by the Lyme spirochetes, your immune system makes antibodies to fight the infection. Tests that measure antibody levels are indirect tests because they measure the body’s response to infection rather than the presence of the bacteria themselves.

During the first 4-6 weeks after exposure, most people have not developed the antibody response that the test measures. Treatment should not be delayed pending a positive test result if the suspicion of Lyme disease is high (exposure, tick bite, possible rash).

Two primary antibody tests are used to diagnose Lyme disease, the ELISA and the western blot. Doctors commonly order an ELISA first to screen for the disease and then confirm the disease with a western blot. However, current ELISA tests are not sensitive enough for screening and may miss over half the true cases. Because of this, the best antibody test to use for diagnosis is the western blot.

Western Blot Test

The read-out from the western blot looks like a bar code. The pattern produced by running the test with your blood is compared to a template pattern that represents known cases of Lyme disease. If your blot has bands in the right places, and the right number of bands, it is positive. Some of the bands are more significant than others and your doctor may decide you have Lyme disease even if your western blot does not have enough bands or the right bands to be reported to the Centers for Disease Control and Prevention (CDC) for surveillance purposes.

Different laboratories use different methods and criteria, so you can have a positive test result from one lab and a negative test result from another. Lyme disease is known to inhibit the immune system and twenty to thirty percent of patients have falsely negative antibody tests.

Other tests

Two other tests that may be used to diagnose Lyme disease are PCR and antigen detection tests. Polymerase chain reaction (PCR) multiplies a key portion of DNA from the Lyme bacteria so that it can be detected. While PCR is highly accurate when the Lyme DNA is detected, it produces many false negatives. This is because Lyme bacteria are sparse and may not be in the sample tested. Antigen detection tests look for a unique Lyme protein in fluid (e.g. blood, urine, joint fluid). Sometimes people whose indirect tests are negative are positive on this test.

Recommended labs

CALDA recommends that you use a CLIA- and Medicare-approved lab that specializes in testing for tickborne diseases and reports all bands on the western blot. The healthcare professional ordering the test must ask the lab to report all bands except in the case of IGeneX, which automatically reports all bands. Blots may still vary in sensitivity.

IGeneX www.igenex.com 800-832-3200

Stony Brook www.path.sunysb.edu/labs/ticklab/ticklab.htm 631-444-3824

MDL www.mdlab.com 877-269-0090

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