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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, doctors do not recommend antibiotics 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 - 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 technically a spirochete, which is a bacteria-like organism. In the United States, B. burgdorferi commonly infects rodents and other small mammals, birds, snakes, lizards, and frogs. White-footed mice are the main reservoir for this Lyme disease-causing organism. In epidemiology terms, reservoir refers to the habitat where an infectious organism lives and multiplies.
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 tick and is transmitted when the tick bites and feeds on a new host.
Ticks are the vectors for Lyme disease transmission. In epidemiology, a vector is an insect that carries the infectious organism from the reservoir and transmits it to a host (such as a human or deer). Hosts provide the blood meal for ticks. In the case of Lyme disease, white-footed mice are considered reservoir hosts since they function as both reservoir and host.
In the United States, there are two species of ticks associated with Lyme disease. In the U.S. Northeast and North Central states, it is the blacklegged tick, Ixodes scapularis, also known as the deer tick. In the U.S. Northwest states, it is the blacklegged tick Ixodes pacificus.
The blacklegged tick has a 2-year life cycle in which it goes through three stages:
The nymph stage (May-July) is the most critical time for Lyme disease infection:
Lyme disease is only transmitted through ticks. You cannot catch Lyme disease from a person who has the condition. 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 borne 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.
If you spend time outdoors in tick-infested areas, avoid wooded and bushy areas. 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 a blacklegged tick bite. The risk depends on several factors.
Locations in the U.S. Lyme disease was named for a town in Connecticut where the first American cases of the disease were described. Lyme disease has been reported in nearly all U.S. states. However, nowadays 96% of Lyme disease cases are concentrated in 13 Northeastern and Midwestern states: Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Vermont, Virginia, and Wisconsin.
Worldwide Locations. Pockets of Lyme disease exist around the world. The disease is common in Europe, particularly in forested areas of middle Europe and Scandinavia. The Borrelia family is also responsible for tick infections in Europe but different subspecies (B. garinii and B. afzelii) are more common there and cause slightly different symptoms than the B. burgdorferi spirochete. The infection has also been reported in Russia, China, and Japan.
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.
Symptoms of Lyme disease are diverse, can vary from person to person, and can appear and disappear at different times. Symptoms tend to follow the course of Lyme disease, which typically occurs in three stages:
In the majority of cases, the first sign of Lyme disease is the appearance of a bull's-eye skin rash called erythema migrans (EM). It usually develops about 1 - 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 lymph nodes within weeks to months where it may affect the joints, nervous system, or heart. Symptoms of early disseminated Lyme disease include:
If patients are not treated with antibiotics, infection can spread throughout the body. Symptoms of late Lyme disease can develop months or years after the initial infection and may include:
Lyme disease is a curable condition. Most patients improve after a short course of antibiotics. In rare cases, patients continue to complain of persistent non-specific symptoms, such as fatigue, muscle aches, cognitive problems, and headache lasting years after completing antibiotic treatment for the initial infection. This syndrome is referred to as post-Lyme disease syndrome, which can resemble fibromyalgia or chronic fatigue syndrome (CFS).
In the past, post-Lyme disease syndrome has been called “chronic Lyme disease.” However, based on many reviews of scientific literature, researchers and doctors strongly believe that Lyme disease does not have a chronic state. According to guidelines from the Infectious Diseases Association of America, post-Lyme disease syndrome is the preferred name for this condition.
Patients are considered to have this syndrome if they still have symptoms 6 months after treatment. There must also be definitive evidence that the patient was originally infected by the B. burgdorferi spirochete. If there is no documented evidence of infection, it is likely that the patient never had Lyme disease and is experiencing a new or different type of illness. If the patient did have Lyme disease, symptoms should eventually resolve without additional antibiotic treatments. Antibiotics are not helpful for post-Lyme disease syndrome.
In some rare cases, patients may experience a new onset of symptoms after antibiotic treatment, such as the bull’s-eye rash. Research suggests that repeat symptoms are most likely caused by new infections, not relapses from a previous 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 may develop in one or two large joints such as the knee, elbow, shoulder, wrist, ankle, or hip. Knees are usually affected most.
Patients with Lyme arthritis usually experience sporadic episodes that last anywhere from a few weeks to several months. Fewer than 10% of patients develop chronic arthritis, which usually affects a single joint.
Lyme arthritis usually resolves with a month of antibiotic treatment. If it does not, doctors recommend several years of drug therapy with nonsteroidal anti-inflammatory drugs (NSAIDs) or the anti-malaria drug hydroxychloroquine (Plaquenil, generic). Patients with difficult to treat cases should also 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.
Peripheral Nervous System. The nerves in the peripheral nervous system (PNS) provide the critical connection between the brain and spinal cord and its limbs and organs. Lyme disease causes various types of nerve damage (neuropathies):
Central Nervous System. Lyme disease complications in the central nervous system (CNS) are rare but very serious, since this area includes the brain and spinal cord:
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.
If Lyme disease spreads throughout the body, it can affect other organs. Lyme disease may 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. A diagnosis of Lyme disease is straightforward if the patient meets the following criteria.
If the patient meets these criteria, treatment is often started without confirming the diagnosis with laboratory tests.
Blood tests for detecting antibodies to B. burgdorferi can give false negative results during the first few weeks of infection. During the early stages of disease, a doctor can identify a patient with Lyme disease based on the bull’s-eye rash and other criteria.
The CDC recommends only these tests. Other tests do not have enough scientific evidence to support their use.
If the patient does not have any symptoms of Lyme disease, these tests are not recommended. These tests should not be used to make a diagnosis of Lyme disease in patients who do not have obvious symptoms or findings of the disease. This is because both false positive and false negative results are common with these tests.
The polymerase chain reaction (PCR) test detects the DNA of the bacteria that causes Lyme disease. It is sometimes used for select patients 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.). For most patients, standard blood antibody tests are preferred.
Many other infections and medical conditions can produce fever, headache, muscle aches, fatigue, and some of the neurologic or cardiac features of early Lyme disease. Some are transmitted by the same tick as Lyme disease.
Co-Infections Transmitted by the Ixodes Tick. Babesiosis and human granulocytic anaplasmosis (HGA), as well as new emerging infections, are transmitted by the same tick that carries Lyme disease. People may be co-infected with one or more of these infections, all of which can cause flu-like symptoms. If these symptoms persist and there is no rash, it is less likely that Lyme disease is present.
Other Tick-Borne Infections. A number of other tick-borne diseases may resemble Lyme disease. The most important of these is southern tick-associated rash illness (STARI), which is caused by the bite of the Lone star tick. It causes a rash very similar to Lyme disease.
Allergic Reactions and Insect Bites. If a rash appears hours (rather than days) after a tick bite, it is most likely an allergic reaction to the tick, not a symptom of Lyme disease. An allergic rash may also be circular, like that from Lyme disease. In addition, not every rash seen in regions where Lyme disease is common is caused by a tick. The bites of many other insects such as spiders can cause a skin reaction, but they do not resemble the bull’s-eye rash of Lyme disease.
Other Diseases. Chronic fatigue and joint and muscle aches are common symptoms of post-Lyme disease syndrome. These symptoms can also be caused by other conditions, including mononucleosis, chronic fatigue syndrome, and fibromyalgia. Early neurologic symptoms of Lyme disease (headache, stiff neck, and fatigue) may be mistaken for viral meningitis.
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.
A single dose of the antibiotic doxycycline may be given in situations that meet all of the following conditions.
In general, the risk of developing Lyme disease after being bitten by a tick is only 1 - 3%. However, patients who have removed attached ticks from themselves should inform their doctors. Patients who have been bitten by a tick should be monitored for up to 30 days to make sure they do not develop symptoms of Lyme disease, especially the bull’s-eye rash. If you do develop a skin lesion or flu-like symptoms during this time, be sure to tell your doctor.
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, patients develop an abnormal heartbeat (Lyme carditis).
All of these conditions are treated with 10 - 28 days with antibiotics. The exact number of days depends on the drug used and the patient’s response to it. Antibiotics for treating Lyme disease generally include:
Other types of antibiotics, such as macrolides, are not recommended for first-line therapy.
Side Effects of Antibiotics. The most common side effects of nearly all antibiotics are gastrointestinal problems, including cramps, nausea, vomiting, and diarrhea. Allergic reactions can also 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 as severe or life-threatening as anaphylactic shock. Some drugs, including certain over-the-counter medications, interact with antibiotics. Patients should report to their doctors all medications they are taking.
Most cases of Lyme disease involve a rash and flu-like symptoms that resolve within 1 month of antibiotic treatment. However, some patients go on to develop late-stage Lyme disease, which includes Lyme arthritis and neurologic Lyme disease.
Slightly more than half of patients infected with B. burgdorferi develop Lyme arthritis. About 10 - 20 % of patients develop neurologic Lyme disease. A very small percentage of patients 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 - 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, patients with arthritis may need intravenous antibiotics. A 2 - 4 week course of intravenous ceftriaxone is used for treating severe cases of neurological Lyme disease. For milder cases, 2 - 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 a controversial issue. Most doctors 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 Clostridiumdifficile, and can also cause the patient 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 patients 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. Any such therapies should be discussed with a doctor. Newsletters and Internet sites have cropped up in recent years advertising untested treatments to patients with symptoms of Lyme disease who are frustrated with standard medical treatment. Some remedies are dangerous, and most are ineffective.
The Food and Drug Administration (FDA) has warned people not to use an alternative medicine product called bismacine (also known as chromacine). This injectable product contains high amounts of bismuth, a heavy metal that can be poisonous. People who have taken bismacine have experienced heart and kidney failure, and one death has been reported. Although some people claim that bismacine can help treat Lyme disease, it is not approved for the treatment of any illness or condition.
Generally, manufacturers of herbal remedies and dietary supplements do not need FDA approval to sell their products. Just like a drug, herbs and supplements can affect the body's chemistry, and therefore have the potential to produce side effects that may be harmful. There have been a number of reported cases of serious and even lethal side effects from herbal products. Always check with your doctor before using any herbal remedies or dietary supplements.
Everyone should avoid specific tick-infested areas, including tall grass, woods, and bushes where ticks tend to congregate. If this is not possible, people should take additional preventive measures. The U.S. Centers for Disease Control (CDC) also recommends:
Mowing the grass regularly, clearing away leaves, and placing wood chips as a barrier around a lawn can help greatly reduce the tick population.
Permethrin for the Lawn. Insecticides can significantly reduce tick infestation. Insecticides should be applied in late spring or early fall in a strip a few feet wide along the perimeter of the lawn where small animals are likely to enter or live.
The most commonly used insecticides are pyrethrins, which are compounds derived from the Chrysanthemum family. They are available as natural products or in synthetic forms (permethrin). They are poisons that affect the nerve system of insects. However, they are safe, particularly the natural products, and for humans and pets. All pyrethrins are highly toxic for certain fish and slightly toxic for birds, such as mallard ducks. Some people do experience an allergic reaction to them. As with all insecticides, there is some concern about the possible consequences of long-term exposure. But to date there is no evidence of any harm.
Cardboard tubes stuffed with permethrin-treated cotton are available in hardware stores. The tubes are placed where mice can find them (dense, dark brush) and collect the cotton for lining their nests. The pesticide on the cotton kills any immature ticks that are feeding on the mice. Best results are obtained with regular applications early in the spring and again in late summer.
Other Pesticides. Other tick-killing spray pesticides that have been used include those containing diazinon, chlorpyrifos, and carbaryl. Animal studies have reported severe toxic effects associated with these chemicals. Some of these chemicals are being phased out for home use. Parents should balance the effects of a very negligible risk for a highly treatable infection against excessive use of possibly harmful chemicals.
Anyone who walks or camps in the woods during tick season should wear protective clothing, including:
Simply washing clothes will not kill ticks. After being outdoors, people should run their clothes through a dryer at high temperature for a half hour. Spraying clothes with solutions containing permethrin (Permanone, Duranon, and Permakill) provides additional protection. Keep in mind that these sprays should not be applied to the skin. Clothes should not be retreated with permethrin for 48 hours unless they have been washed after the first application.
DEET. Most insect repellents contain the chemical DEET (N,N-diethyl-meta-toluamide), which remains the gold standard of currently available mosquito and tick repellents. DEET has been used for more than 40 years and is safe for most children when used as directed. Comparison studies suggest that DEET preparations are the most effective insect repellents now available.
Concentrations range from 4 to almost 100%. The concentration determines the duration of protection. Most adults and children over 12 years old can use preparations containing a DEET concentration of 20 - 35% (such as Ultrathon), which provides complete protection for an average of 5 hours. Higher DEET concentrations may be necessary for adults who are in high-risk regions for prolonged periods.
DEET products should never be used on infants younger than 2 months. According to the Environmental Protection Agency, DEET products can safely be used on all children age 2 months and older. The EPA recommends that parents check insect repellent product labels for age restrictions.
If there is no age restriction listed, the product is safe for any age. The American Academy of Pediatrics recommends that children use concentrations of 10% or less; 30% DEET is the maximum concentration that should be used for children. In deciding what concentration is most appropriate, parents should consider the amount of time that children will be spending outside and the risk of insect bites and insect-borne disease.
When applying DEET, take the following precautions.
Picaridin. Picaridin, also known as KBR 3023 or Bayrepel, is an ingredient that has been used for many years in repellents sold in Europe, Latin America, and Asia. A product containing 7% picaridin is now available in the United States. Picaridin can safely be applied to young children and is also safe for women who are pregnant or breastfeeding. Insect repellents containing DEET or picaridin work better than other products for protection against ticks.
Tick Check. Studies indicate that ticks begin transmitting the Lyme disease spirochete within 36 – 48 hours after attachment. Removing a tick within 48 hours can reduce your chance of contracting Lyme disease. The following tips are important for self-inspection:
Tick Removal. If an attached tick is discovered, there is no reason to panic. Not all ticks are infected, and not everyone who is bitten by a tick will get Lyme disease. 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:
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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