Lyme disease and related tick-borne infections
Lyme disease is caused by the bacterium Borrelia (B.) burgdorferi, which is transmitted through the bite of a deer tick. Either nymph or adult ticks can transmit B. burgdorferi.
- Anyone exposed to deer ticks is at risk for Lyme disease. Deer ticks thrive in grassy areas that have low sunlight and high humidity.
- Nymph ticks are more active during the summer months, and their small size makes them more difficult to spot than adult ticks. Consequently, the risk for acquiring Lyme disease tends to be higher during the summer than the spring or fall. Risk is lowest in the winter when ticks become inactive.
- Avoid tick-infested areas such as tall grass, woods, and bushes.
- If you walk or hike through these areas, wear long pants and long sleeves. Light-colored clothes will make it easier to spot ticks.
- Use a tick repellant (DEET, picardin) on your exposed skin and clothes. Spray your clothes with permethrin (but NOT your skin).
- After you return home, do a tick check. Removing infected ticks within 48 hours of attachment significantly reduces the risk of developing Lyme disease.
- A bull's eye rash, called erythema migrans, is the most definitive sign of Lyme disease infection. This rash usually develops 1 - 2 weeks after the tick bite.
- Other symptoms, such as joint pains, fever, chills, and fatigue, may accompany the rash.
- If Lyme disease is not treated, more severe symptoms and complications can occur. These may include arthritis, neurologic symptoms, and heart problems.
Most cases of Lyme disease can be prevented or cured with prompt antibiotic treatment following a deer tick bite. If a preventive antibiotic is needed, a single dose of doxycycline may 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 vector-borne disease in the United States. Vector-borne infections are transmitted by insects.
The Lyme disease infection in the U.S. is caused by a spirochete called Borrelia (B.) burgdorferi. A spirochete is a bacteria-like organism with a cylinder-like shape surrounded by an outer membrane.
The vector that carries B. burgdorferi in the U.S. Northeast and North Central states is the blacklegged tick (also called deer tick) Ixodes scapularis. In the U.S. Northwest states, it is the blacklegged tick Ixodes pacificus. The tick goes through three stages over the course of about 2 years:
- It is born from eggs as a larva.
- It develops into the nymph stage.
- It develops into the adult stage.
Lyme disease depends on three factors coming into close contact:
- The Borrelia (B.) burgdorferi spirochete
- The spirochete's host, the Ixodes scapularis tick
- A mammal for the tick to bite
The cycle of infection is related to the tick's life cycle, which requires 2 years to complete:
- The tick typically first picks up the spirochete during its larva stage, when it needs a blood meal to mature further.
- The tick's initial meal is typically blood from the white-footed mouse (or in the Northwest, dusky-footed wood rat), which is commonly infected with Borrelia burgdorferi. After it dines on the infected blood, the tick then becomes a carrier of this spirochete.
- Borrelia burgdorferi lodges in the tick throughout one of both of its following life stages, nymph and adult. It is during these stages that the infection is passed on to other animals, including humans. Nymph ticks emerge around mid-June and can be about the size of poppy seeds. They are very difficult to spot and are estimated to be responsible for 90% of all Lyme disease cases. Adult ticks can be as large as a raisin after feeding, so they are easy to spot, but they usually prefer to dine on blood of the white-tailed deer.
- The infected nymph or adult tick crawls (it does not fly or jump) onto another animal, which can be mice or larger animals such as deer, birds, or humans. If the tick bites these animals, it may then infect them with the B. burgdorferi spirochete. (Infected humans cannot pass the spirochete on to other humans by any means, including infected blood or urine or sexual contact.)
- A tick can feed for several days while being imbedded in the skin, after which it falls off. The tick's bite is painless, however, so only about half of people with Lyme disease recall being bitten.
The two other important infections carried by the Ixodes scapularis tick (deer tick) are human granulocytic anaplasmosis (HGA) and babesiosis. Although they are both borne by the same tick as Lyme disease, all three of these infections are entirely different diseases. Deer ticks can also transmit deer tick virus. In very rare cases, deer tick virus may cause serious brain infection (encephalitis).
Symptoms of Lyme disease are diverse and often occur in early and late phases. They vary widely from person to person. Any one symptom may fail to appear, and symptoms may overlap in various combinations. Death from Lyme disease is extremely rare and occurs only in rare cases when the heart is severely affected.
- Stage 1. In the majority of cases, the first sign of early Lyme disease is the appearance of a bull's-eye skin rash. It usually develops about 1 - 2 weeks after the bite, although it may appear as soon as 3 days, and as late as 1 month. In some cases, it is never detected. Flu-like symptoms (joint aches, fever, and general fatigue) commonly develop.
- Stage 2. Untreated, the infection spreads through the bloodstream and lymph nodes within days to weeks, involving the joints, nervous system, and possibly the heart. Multiple rashes may erupt in other places. If the infection affects the nervous system in stage 2, it most often affects the facial nerve causing weakness or paralysis of face muscles (Bell's palsy). Nerves of the spine may also be affected.
- Stage 3. If the disease remains untreated, a persistent infection may occasionally develop, sometimes leading to prolonged bouts of arthritis and neurologic problems, such as concentration problems or personality changes. Fatigue is a prominent feature of both early and late stages.
The bull's-eye skin rash, known as erythema migrans (ECM), usually first appears on the thigh, buttock, or trunk in older children and adults, and on the head or neck in young children.
The bull's eye rash, which is considered the classic sign of Lyme disease, may take the following course:
- It can first appear as a pimple-like spot, which expands over the next few days into a purplish circle. The circle may reach up to 6 inches in diameter with a deeper red rim. In some cases the ring is incomplete, forming an arc rather than a full circle.
- The center of the rash often clears or may turn bluish. Or secondary concentric rings may develop within the original ring, creating the bull's-eye pattern. Over the next several weeks, the circular rash may grow to as large as 20 inches across.
- Patients often describe the sensation of the rash as burning rather than itching.
Up to 20% of people infected with Lyme disease do not exhibit the rash. On dark-skinned people, the rash may resemble a bruise. In most patients, any rash fades completely after 3 - 4 weeks, although secondary rashes may appear during the later stages of disease.
A flu-like condition is the most common sign of Lyme infection, and it can occur with or without a rash. Symptoms can last from 5 - 21 days and may include:
- Chills and fever (100 - 103 °F)
- Headache (usually most prominent at the back of the head)
- Joint aches (usually in the large joints)
- Stiff neck
- Swollen glands (in the area around the tick bite or elsewhere)
- Less often, nausea, vomiting, and sore throat occur
Joint pain can arise at the same time as the skin rash. 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, or shoulder. (Knees are usually affected most.)
Common Neurologic Symptoms. Neurologic symptoms can first appear while the initial skin rash is still present or within 6 weeks after its disappearance. Sometimes they are the first symptoms that the patient experiences, but sometimes they may not occur until many months after the tick bite. The most common neurologic symptoms include headaches, sleep problems, and mood disturbance. Memory problems can also occur, as well as nerve damage in arms and legs. Neurologic symptoms typically improve or resolve within a few weeks or months, even in untreated patients.
Bell's Palsy. In some patients, the facial nerve is affected, which results in Bell's palsy. This is a sudden weakness and drooping of the facial muscles and eyelid on one side of the face. Nerves around the facial area may also cause numbness, dizziness, double vision, and hearing changes.
Symptoms of Meningitis. Meningitis can occur if the infection takes place in the membranes that surround the brain and spinal cord (the meninges). This can cause:
- Episodes of headache not relieved by over-the-counter medication
- Mild stiff neck
- Sensitivity to light
Symptoms of Lyme Encephalopathy. In some cases of untreated disease, the infection causes a condition called Lyme encephalopathy or neuroborreliosis. This causes the following symptoms:
- Unexplained mood changes
- Trouble concentration and remembering
- Feelings of "pins and needles" or numbness in the arms or legs
Heart symptoms, such as an irregular heartbeat, may develop several weeks after infection, but this is not very common. In rare cases, Lyme disease may cause eye inflammation (conjunctivitis).
Lyme disease is the most commonly reported insect-borne illness in the United States. About 25,000 cases of Lyme disease are reported in the U.S. each year.
Anyone exposed to ticks is at risk for Lyme disease and other tick-borne diseases. Pets are also at risk. Naturally, anyone who is regularly outside in areas where tick rates are high has a greater than average risk for becoming infected.
Age. The highest reported incidence of Lyme disease occurs among children 5 - 14 years old and adults 45 - 54 years old.
Sex. Men and women are equally at risk.
In general, the risk for developing Lyme disease after a tick bite is only 1 - 3%. The risk varies depending on different factors:
- The longer the tick has fed, the greater the risk.
- Nymph ticks carry a greater risk than adult ticks, probably because they are often too small to be detected (about the size of a pinhead). In addition, only nymph ticks that are at least partially swollen when removed pose any significant risk. (Swelling suggests that they have been feeding for a prolonged period.)
Locations in the U.S. Lyme disease has been reported in nearly all U.S. states. However, most Lyme disease cases are concentrated in the northeastern, mid-Atlantic, and north central states. Although Lyme disease was named for a town in Connecticut where the first American cases of the disease were described, in recent years New Jersey, Pennsylvania, Wisconsin, New York, and Massachusetts have reported the greatest number of cases.
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) may be more common there and cause slightly different symptoms. The infection has also been reported in Russia, China, and Japan.
Deer 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, groundcover 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 Lyme disease onset is from June through August, and the lowest risk is from December through March.
Prompt treatment with antibiotics is very effective in curing Lyme disease in nearly all infected people, including children. However, untreated Lyme disease can lead to complications.
People at highest risk for persistent symptoms are those who go the longest before treatment. Fortunately, public vigilance has significantly reduced the rates of late-stage Lyme disease. Antibiotics given at late stages will relieve symptoms in most people, although about 5% may continue to have problems.
Left untreated, Lyme disease can spread (disseminate). The infection may affect almost any part of the body and cause the following complications:
- Severe arthritis
- Persistent fatigue
- Mood disturbances and loss of concentration
- Neuropathy (numbness, tingling, or other odds sensations in the hands, arms, feet or legs)
- Life-threatening disorders affecting the heart, lungs, or nervous system can occur, but are very rare.
About 60% of untreated patients develop arthritis, which usually affects a knee or other large joint. About 10 - 20% of patients develop neurological or heart problems.
Persistent neurological symptoms include headache, attention and memory problems, and depression. Patients may also experience pain or tingling in legs or arms (peripheral neuropathy), numbness, or facial paralysis (Bell’s palsy). Neurologic symptoms generally resolve and improve within a year.
The main heart complications are electrical conduction problems caused by the infection, which can result in an abnormally slow heart rate.
Pregnancy. 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 a curable condition. Nearly all patients (95%) improve after a short course of antibiotics. In very 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, which resembles chronic fatigue syndrome (CFS) or fibromyalgia, is referred to as post-Lyme disease syndrome. In the past, it 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 the 2006 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. Most important, there must 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.
Diseases with Similar Symptoms
Many other illnesses can mimic Lyme disease.
Other infections 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) 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 Spirochete Infections. Leptospirosis is a spirochete infection spread through animals or contaminated water that most often affects young people during the summer or fall.
Other Tick-Borne Infections. A number of other tick-borne diseases may resemble Lyme disease, although they are more common in parts of the U.S. where Lyme disease is less prevalent.
- Tick-borne relapsing fever (TBRF), a flu-like illness that occurs in mountainous areas of the West during the summer, may be misdiagnosed as Lyme disease. The antibiotic doxycycline may be prescribed for patients who have been bitten by ticks suspected of carrying TBRF, to help prevent development of the disease.
- Rocky Mountain spotted fever, which is also transmitted by ticks, is most prevalent in the south central and southeastern parts of the United States, but occurs throughout North and South America. The most characteristic symptom is a spotty rash that appears 5 - 10 days after infection. The disease is caused by ticks that carry the bacterial organism Rickettsia rickettsii, and is considered the most severe tick-borne illness in the United States. Unlike Lyme disease, which is rarely fatal, untreated Rocky Mountain spotted fever causes death in about 10% of all cases. Recent outbreaks of Rocky Mountain spotted fever have been linked to increases in wild dog populations.
- A tick-borne infection called by human monocyte ehrlichiosis (HME), carried by the Lone Star tick, strongly resembles Lyme disease, including a similar rash, but it is not caused by the Lyme spirochete. HME has been identified in patients who live in the southern United States.
Allergic Reaction to the Tick. If a rash, even ring-shaped, 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.
Other Insect Bites. Not every rash seen in regions where Lyme disease is common is caused by a tick. The bites of many insects and spiders can cause a skin reaction.
A number of conditions cause chronic fatigue and joint and muscle aches that resemble descriptions of post-Lyme disease syndrome:
- Mononucleosis (this viral infection is common in adolescents)
- Chronic fatigue syndrome (CFS)
- Depression (may include persistent fatigue and vague aches and pains)
The early neurologic symptoms of Lyme disease (headache, stiff neck, and fatigue) can easily be mistaken for viral meningitis. Children with viral meningitis are likely to have a higher fever. Most patients with Lyme disease often have other symptoms, such as the bull's-eye rash.
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:
- Lives in an area of tick-infestation
- Has the tell-tale bulls-eye rash (erythema migrans)
- Has other symptoms (headache, joint aches, malaise, flu-like symptoms)
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 may give false results during the early stages of the disease. They are more accurate if used at least a month after the initial infection. The U.S. Centers for Disease Control and Prevention (CDC) recommends a two-step process for Lyme disease blood tests:
- ELISA or IFA Test. The first tests used are either enzyme-linked immunosorbent assay (ELISA) or an indirect fluorescent antibody (IFA) test. ELISA is the immune test used most often for Lyme disease. (The IFA test is less accurate but may be used when ELISA isn't available.) ELISA measures antibodies that are directed against the B. burgdorferi spirochete. A newer variant is a rapid test (PreVue) that can provide results within an hour. Positive results from any of these tests still require confirmation with a Western blot test. Negative results do not require further testing.
- Western Blot. If the ELISA or IFA test is positive or uncertain, it is followed by the Western blot test. This test is more accurate and is very helpful in confirming the diagnosis. The Western blot creates a visual graph showing bands of different colors or shading that laboratories use to interpret the immune response.
The CDC recommends only these tests. Other tests -- such as urine antigen, immunofluroescent staining, and lymphocyte transformation -- 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.
- False positive results occur when the test suggests the presence of the disease, but the person does not actually have an active infection.
- False negative results miss the actual presence of the disease. These results are also common. (If the results are negative but Lyme disease is highly suspected, the doctor will probably prescribe antibiotics anyway.)
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.
Antibiotics are the drugs used for treating all phases of Lyme disease. In nearly all cases they can cure Lyme, 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:
- The tick is still attached to the patient and is positively identified as an adult or nymphal I. scapularis (the tick that carries the Lyme disease B. burgdorferi spirochete).
- Doxycycline treatment can be given within 72 hours of the tick bite.
- There is proof that at least 20% of ticks in that geographic area are infected with B. burgdorferi.
- It is safe for the patient to receive doxycycline (this drug should not be given to pregnant women or children younger than 8 years of age).
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 tell-tale bull’s-eye rash. If you do develop a skin lesion or flu-like illness during this time, be sure to tell your doctor.
The early stages of Lyme disease usually involve classic 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 of 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:
- Doxycycline. This antibiotic is effective against both Lyme disease and human granulocytic anaplasmosis (HGA) and so is the standard antibiotic for any patient over 8 years old (except pregnant women). Doxycycline cannot be used routinely in children under 8 years old. It is a form of tetracycline and as such discolors teeth and inhibits bone growth. It can also cause birth defects, so it should not be used during pregnancy.
- Either amoxicillin (one of the penicillins) or cefuroxime (Ceftin, generic) -- an antibiotic known as a cephalosporin -- are the alternative treatments for young children and some adults. Amoxicillin is the first choice and also probably the best antibiotic for pregnant women. Unfortunately, many people are allergic to penicillin. In addition, strains of bacteria are emerging that are resistant to penicillins.
- Intravenous ceftriaxone -- another cephalosporin -- may be warranted if there are signs of infection in the central nervous system (the brain or spinal region) or heart.
- 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. These reactions can range from mild skin rashes to rare but severe, even life-threatening, 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, a condition 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 superbugs.
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:
- Use of tick repellant
- Routine tick checks -- removal of infected ticks within 48 hours of attachment substantially reduces the likelihood of transmission.
- Prompt antibiotic prevention for tick bites -- although this method is controversial, the CDC concludes that it is probably beneficial.
- Removing brush and leaves -- such landscaping measures can reduce transmission rates by 50 - 90%.
- Applying pesticides to yards once or twice per year, which can decrease the number of ticks by 68 - 100%
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, 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 versus excessive use of possibly harmful chemicals.
Anyone who walks or camps in the woods during tick season should wear protective clothing, including:
- Light-colored clothing -- makes it easier to spot ticks
- Long-sleeved shirts and long pants with cuffs tucked into shoes or socks
- High boots, preferably rubber boots
- Tick-collars for small dogs -- can be worn around a person's ankles over socks or pants
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, 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 repellant 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 mosquito bites and mosquito-borne disease.
When applying DEET, take the following precautions:
- Do not use on the face, and apply only enough to cover exposed skin on other areas.
- Do not over apply and do not use under clothing.
- Do not apply over any cuts, wounds, or irritated skin.
- Parents or an adult should apply repellent to a child and not let the child apply it. They should first put DEET on their own hands and then apply it to the child. They should avoid putting DEET not only near the child's eyes and mouth but also on the hands (since children frequently touch their faces).
- Wash any treated skin after going back inside.
- If using a spray, apply DEET outdoors -- never indoors. Spray repellents should not be applied inside or directly on anyone's face.
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.
Self-Inspection. The tick is unlikely to transmit the infection within 3 days of the bite, but prompt removal is still important. The following tips are important for self-inspection:
- Ticks responsible for Lyme disease are very small and may resemble freckles or scabs.
- People spending time in tick-infested locations should inspect themselves several times a day, including at bedtime.
- Check nonexposed areas, such as the back of the knee, as well as exposed areas. Someone else should check the scalp, back of the neck, and other difficult to reach areas.
- Check clothing as well as skin. A tick on can be hidden in folds or creases.
Tick Removal. If an attached tick is discovered, there is no reason to panic. 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 organism into the body.
The safest and most effective way to remove an attached tick is:
- Grasp the tick's mouth area with clean tweezers as close to the skin as possible. (Take care not to handle it with bare fingers as this can also spread infection.)
- Next, pull upward with a steady even pressure. Do not twist, crush, or squeeze the body area of the tick, because this region contains the infectious organism. In fact, do not be alarmed if some of the mouth parts remain in the skin. They are not infectious.
- Put the tick in a jar or container of alcohol, which will kill it. Some people lay a piece of adhesive tape to the top of the tick and fold it over, without touching the insect. Then they simply throw it away. Tape is also effective for trapping a tick that has not yet attached to the skin.
- Once the tick is removed, wash the bite area with soap and water or with an antiseptic to destroy any contaminating microorganisms. Wash hands as well.
Since dogs, cats and even horses can get Lyme disease, inspect pets for ticks regularly. Symptoms in animals include lameness and lethargy. Dogs are much more likely to get Lyme disease than cats, but both are susceptible. In dogs, symptoms occur 2 - 5 months after a tick bite and include fever, lameness, and lack of appetite. In rare cases, Lyme disease can cause kidney damage in dogs if it is left untreated.
Preventive Products. Products containing permethrin (Bio Spot, EXspot), amitraz (Preventic), or fipronyl (Frontline) can be used safely on dogs. Not all of these products are safe in cats. Only permethrin is also effective against fleas.
Pet Vaccines. 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.
Treatment. As with people, antibiotics almost always cure the infection in animals.
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Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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