lyme disease lyme disease lyme disease, also known as lyme borreliosis, is a vector-borne disease caused by the borrelia bacterium, which is spread by ticks in the genus ixodes. the most common sign of infection is an expanding red rash, known as erythema migrans (em), which appears at the site of the tick bite about a week afterwards. the rash is typically neither itchy nor painful. approximately 70–80% of infected people develop a rash. early diagnosis can be difficult. other early symptoms may include fever, headaches and tiredness. if untreated, symptoms may include loss of the ability to move one or both sides of the face, joint pains, severe headaches with neck stiffness or heart palpitations. months to years later repeated episodes of joint pain and swelling may occur. occasionally shooting pains or tingling in the arms and legs may develop. despite appropriate treatment, about 10 to 20% of those affected develop joint pains, memory problems and tiredness for at least six months. not to be confused with phytophotodermatitis, also known as "lime disease". lyme diseaseother nameslyme borreliosisan adult deer tick (most cases of lyme are caused by nymphal rather than adult ticks)specialtyinfectious diseasesymptomsexpanding area of redness at the site of a tick bite, fever, headache, tirednesscomplicationsfacial nerve paralysis, arthritis, meningitis, heart rhythm irregularitiesusual onseta week after a bitecausesborrelia spread by ticksdiagnostic methodbased on symptoms, tick exposure, blood testspreventionprevention of tick bites (clothing the limbs, deet), doxycyclinemedicationdoxycycline, amoxicillin, ceftriaxone, cefuroximefrequency~476k/year in u.s. (a likely overestimate), 200k/year in europe lyme disease is transmitted to humans by the bites of infected ticks of the genus ixodes. in the united states, ticks of concern are usually of the ixodes scapularis type and must be attached for at least 36 hours before the bacteria can spread. in europe, ixodes ricinus ticks may spread the bacteria more quickly. in north america, the bacteria borrelia burgdorferi and b. mayonii cause lyme disease. in europe and asia, borrelia afzelii, borrelia garinii, b. spielmanii and four other species also cause the disease. the disease does not appear to be transmissible between people, by other animals nor through food. diagnosis is based on a combination of symptoms, history of tick exposure and possibly testing for specific antibodies in the blood. blood tests are often falsely negative in the early stages of the disease. testing of individual ticks is not typically useful. prevention includes efforts to prevent tick bites by wearing clothing to cover the arms and legs and using deet or picaridin-based insect repellents. using pesticides to reduce tick numbers may also be effective. ticks can be removed using tweezers. if the removed tick is full of blood a single dose of doxycycline may be used to prevent the development of infection but is not generally recommended since the development of infection is rare. if an infection develops, a number of antibiotics are effective, including doxycycline, amoxicillin and cefuroxime. standard treatment usually lasts for two or three weeks. some people develop a fever and muscle and joint pains from treatment, which may last for one or two days. in those who develop persistent symptoms, long-term antibiotic therapy has not been found to be useful. lyme disease is the most common disease spread by ticks in the northern hemisphere. infections are most common in the spring and early summer. lyme disease was diagnosed as a separate condition for the first time in 1975 in lyme, connecticut. it was originally mistaken for juvenile rheumatoid arthritis. the bacterium involved was first described in 1981 by willy burgdorfer. chronic symptoms following treatment are known as "post-treatment lyme disease syndrome" (ptlds). ptlds is different from chronic lyme disease, a term no longer supported by scientists and used in different ways by different groups. some healthcare providers claim that ptlds is caused by persistent infection but this is not believed to be true because no evidence of persistent infection can be found after standard treatment. no human vaccines for lyme disease are currently available, although research is ongoing. multiple vaccines are available for the prevention of lyme disease in dogs. signs and symptoms an expanding rash is an initial sign of about 80% of lyme infections. the rash may look like a 'bull's eye', as pictured, in about 80% of cases in europe and 20% of cases in the us. lyme disease can affect several body systems and produce a broad range of symptoms. not everyone with lyme disease has all of the symptoms and many of the symptoms are not specific to lyme disease but can occur with other diseases as well. the incubation period from infection to the onset of symptoms is usually one to two weeks but can be much shorter (days) or much longer (months to years). lyme symptoms most often occur from may to september in the northern hemisphere because the nymphal stage of the tick is responsible for most cases. asymptomatic infection exists but occurs in less than 7% of infected individuals in the united states. asymptomatic infection may be much more common among those infected in europe. early localized infection early localized infection can occur when the infection has not yet spread throughout the body. only the site where the infection has first come into contact with the skin is affected. the initial sign of about 80% of lyme infections is an erythema migrans (em) rash at the site of a tick bite, often near skin folds such as the armpit, groin or back of the knee, on the trunk, under clothing straps, or in children's hair, ears or neck. most people who get infected do not remember seeing a tick or a bite. the rash appears typically one or two weeks (range 3–32 days) after the bite and expands 2–3 cm per day up to a diameter of 5–70 cm (median 16 cm). the rash is usually circular or oval, red or bluish, and may have an elevated or darker center. in about 79% of cases in europe but only 19% of cases in endemic areas of the u.s. the rash gradually clears from the center toward the edges, possibly forming a "bull's eye" pattern. the rash may feel warm but usually is not itchy, is rarely tender or painful and takes up to four weeks to resolve if untreated. the em rash is often accompanied by symptoms of a viral-like illness, including fatigue, headache, body aches, fever and chills but usually not nausea or upper-respiratory problems. these symptoms may also appear without a rash or linger after the rash has disappeared. lyme can progress to later stages without these symptoms or a rash. people with high fever for more than two days or whose other symptoms of viral-like illness do not improve despite antibiotic treatment for lyme disease, or who have abnormally low levels of white or red cells or platelets in the blood, should be investigated for possible coinfection with other tick-borne diseases such as ehrlichiosis and babesiosis. early disseminated infection within days to weeks after the onset of local infection the borrelia bacteria may spread through the lymphatic system or bloodstream. in 10–20% of untreated cases em rashes develop at sites across the body that bear no relation to the original tick bite. transient muscle pains and joint pains are also common. in about 10–15% of untreated people, lyme causes neurological problems known as neuroborreliosis. early neuroborreliosis typically appears 4–6 weeks (range 1–12 weeks) after the tick bite and involves some combination of lymphocytic meningitis, cranial neuritis, radiculopathy and/or mononeuritis multiplex. lymphocytic meningitis causes characteristic changes in the cerebrospinal fluid (csf) and may be accompanied for several weeks by variable headache and, less commonly, usually mild meningitis signs such as inability to flex the neck fully and intolerance to bright lights but typically no or only very low fever. after several months neuroborreliosis can also present otolaryngological symptoms. up to 76.5% of them present as tinnitus, the most common symptom. vertigo and dizziness (53.7%) and hearing loss (16.7%) were the next most common symptoms. in children partial loss of vision may also occur. cranial neuritis is an inflammation of cranial nerves. when due to lyme it most typically causes facial palsy, impairing blinking, smiling and chewing on one or both sides of the face. it may also cause intermittent double vision. lyme radiculopathy is an inflammation of spinal nerve roots that often causes pain and less often weakness, numbness, or altered sensation in the areas of the body served by nerves connected to the affected roots, e.g. limb(s) or part(s) of trunk. the pain is often described as unlike any other previously felt, excruciating, migrating, worse at night, rarely symmetrical, and often accompanied by extreme sleep disturbance. mononeuritis multiplex is an inflammation causing similar symptoms in one or more unrelated peripheral nerves. rarely, early neuroborreliosis may involve inflammation of the brain or spinal cord, with symptoms such as confusion, abnormal gait, ocular movements, or speech, impaired movement, impaired motor planning, or shaking. in north america, facial palsy is the typical early neuroborreliosis presentation, occurring in 5–10% of untreated people, in about 75% of cases accompanied by lymphocytic meningitis. lyme radiculopathy is reported half as frequently, but many cases may be unrecognized. in european adults, the most common presentation is a combination of lymphocytic meningitis and radiculopathy known as bannwarth syndrome, accompanied in 36-89% of cases by facial palsy. in this syndrome, radicular pain tends to start in the same body region as the initial erythema migrans rash, if there was one, and precedes possible facial palsy and other impaired movement. in extreme cases, permanent impairment of motor or sensory function of the lower limbs may occur. in european children, the most common manifestations are facial palsy (in 55%), other cranial neuritis, and lymphocytic meningitis (in 27%). in about 4–10% of untreated cases in the u.s. and 0.3–4% of untreated cases in europe, typically between june and december, about one month (range 4 days-7 months) after the tick bite, the infection may cause heart complications known as lyme carditis. symptoms may include heart palpitations (in 69% of people), dizziness, fainting, shortness of breath, and chest pain. other symptoms of lyme disease may also be present, such as em rash, joint aches, facial palsy, headaches, or radicular pain. in some people, however, carditis may be the first manifestation of lyme disease. lyme carditis in 19–87% of people adversely impacts the heart's electrical conduction system, causing atrioventricular block that often manifests as heart rhythms that alternate within minutes between abnormally slow and abnormally fast. in 10–15% of people, lyme causes myocardial complications such as cardiomegaly, left ventricular dysfunction, or congestive heart failure. another skin condition, found in europe but not in north america, is borrelial lymphocytoma, a purplish lump that develops on the ear lobe, nipple, or scrotum. late disseminated infection lyme arthritis caused this 3-year-old girl's knee to become swollen. though painless, it did make her limp. lyme arthritis occurs in up to 60% of untreated people, typically starting about six months after infection. it usually affects only one or a few joints, often a knee or possibly the hip, other large joints, or the temporomandibular joint. there is usually large joint effusion and swelling, but only mild or moderate pain. without treatment, swelling and pain typically resolve over time but periodically return. baker's cysts may form and rupture. in early us studies of lyme disease, a rare peripheral neuropathy was described that included numbness, tingling or burning starting at the feet or hands and over time possibly moving up the limbs. in a later analysis that discovered poor documentation of this manifestation, experts wondered if it exists at all in the us or is merely very rare. a neurologic syndrome called lyme encephalopathy is associated with subtle memory and cognitive difficulties, insomnia, a general sense of feeling unwell, and changes in personality. lyme encephalopathy is controversial in the us and has not been reported in europe. problems such as depression and fibromyalgia are as common in people with lyme disease as in the general population. there is no compelling evidence that lyme disease causes psychiatric disorders, behavioral disorders (e.g. adhd), or developmental disorders (e.g. autism). acrodermatitis chronica atrophicans (aca) is a chronic skin disorder observed primarily in europe among the elderly. aca begins as a reddish-blue patch of discolored skin, often on the