Lyme disease is caused by the bacterium Borrelia burgdorferi, which is transmitted through the bite of a blacklegged tick, also known as a deer tick.
Most cases of Lyme disease can be prevented or cured with prompt antibiotic treatment. Because most tick bites do not result in Lyme disease, antibiotics are not recommended for every tick bite. If a preventive antibiotic is needed, a single dose of doxycycline will suffice. To treat active disease, antibiotics are usually given for 2 to 4 weeks. Current guidelines do not recommend longer courses of antibiotic treatment for any stage or complication of Lyme disease.
Lyme disease is the most commonly reported tick-borne disease in the United States. Lyme disease is caused by the bacterium Borrelia burgdorferi, which is transmitted through the bite of a blacklegged tick.
Borrelia (B.) burgdorferi is a type of bacterium called a spirochete, due to its spiral shape when seen through a microscope. In the United States, B. burgdorferi commonly infects rodents, principally the white-footed mouse, but other small mammals, birds, snakes, lizards, and frogs can be infected as well.
Blacklegged ticks pick up B. burgdorferi when they bite and feed on an infected white-footed mouse or other animal. The spirochete lodges in the intestine of the tick and is transmitted when the tick bites and feeds on a new host.
In the United States, two species of ticks are associated with Lyme disease:
The blacklegged tick has a 2-year life cycle during which it goes through 3 stages of development:
Ticks are active in all seasons, including winter. However, the most critical time for Lyme disease infection is when the nymph stage is most prevalent (May to July). Ticks usually reside on the forest floor under leaves and sense the warmth or carbon dioxide given off by a passing animal or person.
Keep in mind that:
Lyme disease is only transmitted through ticks. You cannot catch Lyme disease from a person who has the infection. Lyme disease can also infect dogs (and cats), but it cannot be directly transmitted from a dog to a human, unless an infected tick crawls off a dog and bites a person.
Not all ticks are blacklegged ticks, and not all blacklegged ticks are infected. Most people who are bitten by a tick do not get Lyme disease. Still, Lyme disease and other tick-borne infections should not be taken lightly. It is important to take precautions to avoid tick bites.
Human granulocytic anaplasmosis (HGA) and babesiosis are also transmitted by the deer tick Ixodes scapularis. Although HGA, babesiosis, and Lyme disease are caused by the same kind of tick, these infections are entirely different diseases.
Deer ticks can also transmit deer tick virus, a disease related to the deadly tick-borne Powassan virus. In very rare cases, deer tick virus, like Powassan virus, may cause serious brain infection (encephalitis).
New tick-borne diseases, carried by Ixodes ticks as well as other tick species, continue to emerge.
Lyme disease is the most commonly reported insect-borne illness in the United States. About 30,000 cases of Lyme disease are reported to the U.S. Centers for Disease Control and Prevention (CDC) each year. However, the CDC estimates that about 90% of cases go unreported. The total number of Americans diagnosed annually with Lyme disease is most likely closer to 300,000.
The risk of acquiring Lyme disease reflects the risk of sustaining a tick bite. In general, activities that mostly involve the outdoors (such as working in forested areas, camping, hiking, or gardening) increase the risk of a tick bite and, consequently, of Lyme disease.
Other factors that can increase your risk for tick bites include:
Not every tick bite will cause Lyme disease. In general, there is only a small risk for developing Lyme disease after any one blacklegged tick bite. The risk depends on several factors.
Blacklegged ticks thrive in grassy areas that have low sunlight and high humidity. Woodlands and fields are prime habitats, but these ticks can also be found in the long grasses adjacent to beaches. The ticks are not confined to rural settings. In suburban areas, they can live in overgrown lawns, ground cover plants, and leaf litter.
The exact time of year for risk depends on a geographic region's seasons and how they affect the tick's breeding cycle. In general, the highest risk for contracting Lyme disease is from late May through July when nymph ticks are active. The lowest risk is from December through March. However, Lyme disease is a year-round concern. Adult ticks can remain active in the winter as long as the temperature is above freezing.
Symptoms of Lyme disease are diverse, can vary from person to person, and can appear and disappear at different times. Symptoms typically occur in 3 stages:
In the majority of cases, the first sign of Lyme disease is the appearance of a bull's-eye rash called erythema migrans (EM), which surrounds the site of the bite. It usually develops about 1 to 2 weeks after the bite, but can appear as soon as 3 days or as late as 1 month after. In some cases, it is never detected. The rash is often accompanied by flu-like symptoms such as low-grade fever, headache, fatigue, neck pain and stiffness, and body aches.
The bull's-eye skin rash is considered the classic sign of Lyme disease. It usually appears on the thigh, buttock, or trunk in older children and adults, and on the head or neck in younger children.
The bull's-eye rash may take the following course:
If left untreated, the infection can spread through the bloodstream and lymphatic vessels within weeks to months where it may affect the joints, nervous system, or heart. Symptoms of early disseminated Lyme disease include:
If not treated with antibiotics, the infection can become established in many areas of the body. Symptoms of late Lyme disease can develop months or years after the initial infection and may include:
Acute Lyme disease, regardless of stage, is a bacterial infection and hence a curable condition. Most people improve after a course of antibiotics. However, in many instances people continue to complain of persistent non-specific symptoms such as fatigue, muscle aches, cognitive problems, and headache that last for years after completing antibiotic treatment for the initial infection.
This pattern of symptoms is referred to as post-Lyme disease syndrome, which can resemble fibromyalgia or chronic fatigue syndrome. People are considered to have this syndrome if they still have symptoms 6 months after treatment. There must also be definitive evidence that a person was originally infected by the B. burgdorferi spirochete.
If there is no documented evidence of infection, it is likely that the person never had Lyme disease in the first place, and is experiencing a new or different type of illness. If the person did have Lyme disease, symptoms should eventually resolve without additional antibiotic treatments.
Post-Lyme disease syndrome is not a bacterial infection, but possibly an immunologic reaction to a prior (perhaps Borrelia) infection. Antibiotics are not helpful for this condition.
Some people may experience a second or occasionally even a third onset of symptoms (such as the bull's-eye rash) years or even decades after antibiotic treatment. There is no evidence that a prior Lyme infection can relapse. Research indicates that such repeat symptoms are most likely caused by new infections, not relapses from a previous infection. Unlike certain viral infections, an episode of Lyme disease does not protect against future, new infection.
Prompt treatment with antibiotics is very effective in curing Lyme disease in nearly all people. While rare, untreated Lyme disease can spread through the body and lead to complications. People at highest risk for complications are those who go the longest without treatment.
Joint pain is common in all stages of Lyme disease. In early stages of Lyme disease, patients may experience migratory pain in joints, muscles, and tendons. In the later stages of the disease, arthritis localizes into 1 or 2 large joints such as the knee, elbow, shoulder, wrist, ankle, or hip. Knees are usually affected most.
People with Lyme arthritis usually experience sporadic episodes that last from a few weeks to several months. Fewer than 10% of people develop chronic arthritis, which usually affects a single or only a very few joints.
During the acute infection, Lyme arthritis usually resolves with 2 to 3 weeks of antibiotic treatment. If it does not, prolonged therapy with nonsteroidal anti-inflammatory drugs (NSAIDs), such as naproxyn or ibuprofen, is recommended. The anti-malaria drug hydroxychloroquine is also occasionally used, not for its antimalarial properties but for into anti-inflammatory effects.
Some health care providers used to prescribe many months of intravenous antibiotics for late stages of Lyme disease. There is no evidence that this is beneficial, and this treatment approach is becoming less frequent. People with difficult-to-treat cases should seek the advice of a rheumatologist who has experience treating rheumatoid arthritis and similar conditions.
The medical term for neurological problems caused by the Borrelia burgdorferi organism is neuroborreliosis. These complications are associated with late Lyme disease.
When Lyme disease infection spreads to the tissues of the heart it can cause inflammation (carditis). Lyme carditis interferes with the heart's electrical conduction signals. The result is "heart block," the stopping of the electrical impulses that keep the heart beating normally. Heart block can occur very suddenly, and can be fatal. Lyme carditis is one of the most serious complications of Lyme disease.
In Europe (but not in the United States), Lyme disease can also result in myocarditis, an inflammation of the cardiac muscle. In this uncommon condition, the heart fails to contract as strongly as normal and the person develops congestive heart failure, with accumulation of fluid in the lungs or in other areas of the body. It is not clear why this condition is prevalent only in Europe.
If Lyme disease spreads throughout the body, it can affect other organs. Lyme disease may rarely manifest as hepatitis (liver), hearing loss (ears), or keratitis (eyes).
In rare cases, Lyme disease acquired during pregnancy can lead to infection of the placenta and possible miscarriage or stillbirth. Studies indicate that pregnant women infected with Lyme disease can safely be treated with antibiotics without endangering the fetus.
Lyme disease is usually diagnosed based on symptoms and evidence of possible exposure to ticks. Your health care provider may diagnose you with Lyme disease if you:
If these criteria are met, treatment is often started without confirming the diagnosis with laboratory tests. Lab tests for Lyme disease are not recommended for people who do not exhibit any of these symptoms.
Blood tests for detecting antibodies to B. burgdorferi are most reliable several weeks after infection has occurred and are rarely of value during the first 7 to 10 days of illness. During these initial days of infection, these tests can give false negative results (showing no evidence of the disease even though the person actually has it).
Most authorities, including the CDC, recommend a 2-step testing process for Lyme disease:
The CDC recommends only these tests. Although many other tests are widely advertised, they do not have enough scientific evidence to support their use.
The polymerase chain reaction (PCR) test detects the DNA of the bacteria that causes Lyme disease. It is sometimes used for select individuals who have neurological symptoms or Lyme arthritis. The PCR test is performed on spinal fluid collected from a lumbar puncture (spinal tap) or synovial fluid (collected from an affected joint). This test is generally available only in research settings and for most people, standard blood antibody tests are preferred.
Many other infections and medical conditions can produce fever, headache, muscle aches, and fatigue. They can also produce some of the neurologic or cardiac features of early Lyme disease, including a very wide variety of common, generally benign viral illnesses. The same tick that causes Lyme disease can also transmit other infections.
Antibiotics are the drugs used for treating all phases of Lyme disease. In nearly all cases they can cure Lyme disease, even in later stages.
According to guidelines from the Infectious Diseases Society of America (IDSA), people bitten by deer ticks should not routinely receive antibiotics to prevent the disease, especially if Lyme disease is not common in that area. In areas where Lyme disease is prevalent, a single dose of an antibiotic is commonly administered after a tick bite.
A single dose of the antibiotic doxycycline may be given if:
In general, the risk of developing Lyme disease after being bitten by a tick is only 1 to 3%. However, if you have an attached tick or have removed it yourself, be sure to inform your health care provider. Also let your provider know if you develop a bull's-eye rash or any flu-like symptoms in the first 30 days following a tick bite.
The early stages of Lyme disease usually include the bull's-eye rash (erythema migrans) and flu-like symptoms of chills and fever, fatigue, muscle pain, and headache. In rare cases, people develop an abnormal heartbeat (Lyme carditis).
All of these conditions are treated with 14 to 28 days with antibiotics. The exact number of days depends on the drug used and the person's response to it. Antibiotics for treating Lyme disease generally include:
Other types of antibiotics, such as macrolides like azithromycin and clarithromycin, are not recommended for first-line therapy.
Allergic reactions can occur with all antibiotics, but are most common with medications derived from penicillin or sulfa. A reaction could be as minor as a mild skin rash, but could also be severe or life-threatening. Some drugs, including certain over-the-counter medications, interact with antibiotics. Be sure to let your health care provider know all medications you are taking.
Most cases of Lyme disease involve a rash and flu-like symptoms that resolve within 1 month of antibiotic treatment. However, some people go on to develop late-stage Lyme disease, which includes Lyme arthritis and neurologic Lyme disease.
Slightly more than half of people infected with B. burgdorferi develop Lyme arthritis. About 10 to 20 % of people develop neurologic Lyme disease. A very small percentage may develop acrodermatitis chronica atrophicans, a serious type of skin inflammation. These conditions are treated for up to 28 days with antibiotic therapy.
If arthritis symptoms persist for several months, a second 2 to 4 week course of antibiotics may be recommended. Oral antibiotics (doxycycline, amoxicillin, or cefuroxime) are used for Lyme arthritis and acrodermatitis chronica atrophicans.
In rare cases, people with arthritis may need intravenous antibiotics. A 2 to 4 week course of intravenous ceftriaxone is used for treating severe cases of neurological Lyme disease. For milder cases, 2 to 4 weeks of oral doxycycline is an effective option.
In about 5% of cases, symptoms persist after treatment. This condition is referred to as post-Lyme disease syndrome. The treatment of post-Lyme disease syndrome is controversial. Most experts do not recommend continuing antibiotic therapy beyond 30 days. Scientific studies do not show any evidence that the benefits of long-term antibiotic treatment outweigh its risks.
Long-term antibiotic treatment can lead to a serious and difficult-to-treat infection called Clostridium difficile, and can also cause a person to become allergic to the antibiotic. In addition, long-term antibiotic treatment carries its own serious risks, such as the development of antibiotic-resistant super bugs.
Experimental and alternative remedies are not recommended. However, some people may benefit from learning pain control and cognitive behavioral techniques to help them cope with and manage their symptoms.
Some people use vitamin B complex, omega-3 and omega-6 fatty acids (found in primrose oil and fish oils), and magnesium supplements to help relieve symptoms. No evidence suggests that they are beneficial. Always check with your health care provider before using any herbal remedies or dietary supplements.
Newsletters and Internet sites have cropped up in recent years advertising untested treatments to people with symptoms of Lyme disease who are frustrated with standard medical treatment. Some remedies are dangerous, and most are ineffective.
Everyone should avoid specific tick-infested areas, including tall grass, woods, and bushes where ticks tend to congregate. If you are going to be in these areas, it is important to take preventive measures.
The CDC recommends:
Anyone who walks or camps in the woods should wear tick-protective clothing, including:
After being outdoors, you should run your clothes through a dryer at high temperature for at least a half hour. In fact, it may be best to put clothes in a hot dryer for 10 minutes before washing them. Washing clothes does not kill ticks but hot dryers do.
The best insect repellants for protecting against ticks are:
Concentrations range from 10 to 98%. The concentration level determines the duration of protection. The CDC recommends using repellants that contain a DEET concentration of 20 to 30%. (A 30% concentration supplies protection for 5 hours.) DEET is approved for both adults and children, but it should not be used on infants younger than 2 months.
When applying DEET or other insect repellant products:
Picaridin is available in concentrations ranging from 5 to 20%. Stronger concentrations can last up to 8 hours. Picaridin is safe for adults and children but, like all insect repellants, should not be applied on children younger than 2 months.
Do not put a hot match to the tick or try to smother it with petroleum jelly, nail polish, or other substances. This only prolongs exposure time and may cause the tick to eject the Lyme spirochete into the body.
The following is the safest and most effective way to remove an attached tick:
To decrease the tick population around your yard:
Since dogs, cats, and even horses can get Lyme disease, inspect pets for ticks regularly. Discuss with your veterinarian the best tick prevention product for your pet. Lyme disease vaccines are available for dogs, but they do not offer total protection. Veterinarians vary in their use of the vaccines. There is no Lyme disease vaccine for humans.
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Reviewed By: Arnold Lentnek, MD, Infectious Diseases Medical Practice, Clinical Research Center of Connecticut. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team. Author: Julia Mongo, MS.