Tick half burrowed into skin
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What Is Lyme Disease?

Lyme disease is an infection that is transmitted through the bite of a tick infected with a bacterium called Borrelia burgdorferi. Ticks typically get the bacterium by biting infected animals, like deer and mice. Most people who get tick bites do not get Lyme disease. Not all ticks are infected, and the risk for contracting the disease increases the longer the tick is attached to the body.

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bull's-eye rash at the site of a tick bite
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Symptoms: Early Stage

Within one to four weeks of being bitten by an infected tick, most people will experience some symptoms of Lyme disease. A circular, expanding rash (called erythema migrans) at the site of the bite develops in about 70%-80% of cases. Some people report flu-like symptoms at this stage, including fever, chills, headaches, fatigue, swollen lymph nodes, joint pain, and muscle aches.

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Lyme disease erythema rash on young girl's chest
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Symptoms: As the Infection Spreads

If the disease is not detected and treated in its early stages, it can extend to more areas of the body, affecting the joints, heart, and nervous system (after several weeks to months after the initial bite). Additional rashes may occur, and there may be intermittent periods of pain and weakness in the arms or legs. Facial-muscle paralysis (Bell's palsy), headaches, and poor memory are other symptoms at this stage, along with a rapid heartbeat and some loss of control of facial muscles.
 

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swollen knees of a patient with osteoarthritis
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Symptoms: Late-Stage Disease

This is the most serious stage of the disease, when treatment was either not successful or never started (usually occurring many months after the initial bite). Joint inflammation (arthritis), typically in the knees, becomes apparent, and may become chronic. The nervous system can develop abnormal sensation because of disease of peripheral nerves (peripheral neuropathy), and confusion. Heart problems are less common, but can include inflammation of the heart muscle and an irregular beat.

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Three different black-legged (deer) ticks
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Do All Ticks Transmit Lyme Disease?

No. In the northeastern and north-central U.S., the black-legged tick (or deer tick) transmits Lyme disease. In the Pacific coastal U.S., the disease is spread by the western black-legged tick. Other major tick species found in the U.S., including the lone star tick and the dog tick, have NOT been shown to transmit the Lyme disease bacterium. But beware: Lyme disease has been reported in all 50 states, as well as in Canada, Europe, Asia, Australia, and South America.

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Man petting dog on beach in Nantucket
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How Lyme Disease is NOT Spread

You can't catch Lyme disease by being around an infected person. And although pets can become infected by a tick, they cannot transmit the disease to humans unless an infected tick falls off the animal and then bites a person. Insects such as mosquitoes, flies, or fleas cannot spread the disease to humans either. Only infected ticks have that honor.

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Lab worker holding vial of blood
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Diagnosing Lyme Disease

Doctors can diagnose the disease through physical findings such as a "bull's-eye" rash along with a history of symptoms. But not everyone has the rash, and not everyone can recall being bitten. Special blood tests can be taken three to four weeks after suspected contact to confirm the diagnosis. Other tests, such as a spinal tap or skin biopsy, may be done to help diagnose or rule out other conditions.

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Blue and white capsule between finger and thumb
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Treating Lyme Disease

Most Lyme disease is curable with antibiotics, particularly when the infection is diagnosed and treated early.  Later stages might require longer-term, intravenous antibiotics.

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Lyme disease bacteria (Borrelia burgdorferi)
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Is There a Lyme Disease Vaccine?

Currently, there is no human vaccine for Lyme disease. A vaccine was developed years ago for use in high-risk areas, but it is no longer available. 

Illustrated here: Borrelia burgdorferi bacterium.

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golfer sprays caddy with insect repellent
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Preventing Lyme Disease

Avoid tick bites whenever possible by staying clear of grassy or wooded areas, especially May to July. Cover your body head-to-toe when entering possible tick-infested areas. Apply an insect repellent containing DEET directly to your skin. Insect repellents containing permethrin can be applied to clothes to kill ticks on contact, but never apply to the skin. When coming in from outdoors inspect your body thoroughly for ticks; do the same for pets. Wash your skin and scalp to knock off any ticks that are only loosely attached.

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Illustration of tweezers pulling tick from skin
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How to Remove a Tick

 If you have a tick, it is important to remove it properly. Using fine-tipped tweezers, grasp the part of the tick that's closest to your skin -- you want to grab the head, not the belly. Slowly pull the tick straight out, without twisting it. Wash the bite site with soap and warm water. Throw the dead tick into the trash. Do not use a lit match, nail polish, petroleum jelly, or other topical agents in an attempt to remove a tick.

 

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Sources | Medically Reviewed on 01/21/2016 Reviewed by David Zelman, MD on January 21, 2016

IMAGES PROVIDED BY:

(1)   Interactive Medical Media LLC
(2)   James Gathany / CDC
(3)   Dr. P. Marazzi / Photo Researchers, Inc.
(4)   SPL / Photo Researchers, Inc.
(5)   Scott Bauer / USDA, Kenneth H. Thomas / Photo Researchers, Inc.(inset) and James Gathany / CDC
(6)   Barbara Peacock / Photographer’s Choice
(7)   Thinkstock Images
(8)   Stockxpert
(9)   3D4Medical.com
(10) AFP / Getty Images
(11) CDC

REFERENCES:

American College of Rheumatology.
American Lyme Disease Foundation.
Centers for Disease Control and Prevention.
Medscape Reference.
National Institute of Allergy and Infectious Diseases.
ScienceDaily.
The Nemours Foundation.

Reviewed by David Zelman, MD on January 21, 2016

This tool does not provide medical advice. See additional information.

THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional medical advice, diagnosis or treatment and should not be relied on to make decisions about your health. Never ignore professional medical advice in seeking treatment because of something you have read on the WebMD Site. If you think you may have a medical emergency, immediately call your doctor or dial 911.