Adult deer tick.
They can be Lyme disease carriers. Nymphal deer ticks are about the size of a poppy seed.
Common bullseye rash pattern associated with Lyme Disease.
The classic sign of early local infection is a circular, outwardly expanding rash called erythema chronicum migrans (also erythema migrans or EM), which occurs at the site of the tick bite 3 to 32 days after being bitten. The rash is red, and may be warm, but is generally painless. Classically, the innermost portion remains dark red and becomes hardened; the outer edge remains red; and the portion in between clears – giving the appearance of a bullseye. However, the partial clearing is uncommon, and thus a true bullseye occurs in as few as 9% of cases.
Ixodes scapularis, the primary vector of Lyme disease in eastern North America.
Lyme disease is the most common tick-borne disease in the Northern Hemisphere. Borrelia (the genus of bacteria which cause Lyme disease) is transmitted to humans by the bite of infected hard ticks belonging to several species of the genus Ixodes. Early manifestations of infection may include fever, headache, fatigue, depression, and a characteristic skin rash called erythema migrans. Left untreated, late manifestations involving the joints, heart, and nervous system can occur. In a majority of cases, symptoms can be eliminated with antibiotics, especially if diagnosis and treatment occur early in the course of illness. Late, delayed, or inadequate treatment can lead to late manifestations of Lyme disease which can be disabling and difficult to treat.
Symptoms
Lyme disease can affect multiple body systems, producing a range of potential symptoms. Not all patients with Lyme disease will have all symptoms, and many of the symptoms are not specific to Lyme disease but can occur in other diseases as well. The incubation period from infection to the onset of symptoms is usually 1–2 weeks, but can be much shorter (days), or much longer (months to years). Symptoms most often occur from May through September because the nymphal stage of the tick is responsible for most cases. Asymptomatic infection exists but is found in less than 7% of infected individuals in the United States. Asymptomatic infection may be much more common among those infected in Europe.
Cause
Borrelia bacteria, the causative agent of Lyme disease. Magnified 400 times.
Lyme disease is caused by Gram-negative spirochetal bacteria from the genus Borrelia. At least 11 Borrelia species have been described, 3 of which are Lyme related. The Borrelia species known to cause Lyme disease are collectively known as Borrelia burgdorferi sensu lato, and have been found to have greater strain diversity than previously estimated.
Three closely-related species of spirochetes are well-established as causing Lyme disease and are probably responsible for the large majority of cases: B. burgdorferi sensu stricto (predominant in North America, but also in Europe), B. afzelii, and B. garinii (both predominant in Eurasia). Some studies have also proposed that B. bissettii and B. valaisiana may sometimes infect humans, but these species do not seem to be important causes of disease.
Lyme disease is diagnosed clinically based on symptoms, objective physical findings (such as erythema migrans, facial palsy, or arthritis), a history of possible exposure to infected ticks, as well as serological tests.
When making a diagnosis of Lyme disease, health care providers should consider other diseases that may cause similar illness. Not all patients with Lyme disease will develop the characteristic bulls-eye rash, and many may not recall a tick bite. Laboratory testing is not recommended for persons who do not have symptoms of Lyme disease.
Diagnosis
Because of the difficulty in culturing Borrelia bacteria in the laboratory, diagnosis of Lyme disease is typically based on the clinical exam findings and a history of exposure to endemic Lyme areas. The EM rash, which does not occur in all cases, is considered sufficient to establish a diagnosis of Lyme disease even when serologies are negative. Serological testing can be used to support a clinically suspected case but is not diagnostic. Clinicians who diagnose strictly based on the CDC Case Definition for Lyme may be in error, since the CDC explicitly states that this definition is intended for surveillance purposes only and is “not intended to be used in clinical diagnosis.”
Diagnosis of late-stage Lyme disease is often difficult because of the multi-faceted appearance which can mimic symptoms of many other diseases. For this reason, Lyme has often been called the new “great imitator”. Lyme disease may be misdiagnosed as multiple sclerosis, rheumatoid arthritis, fibromyalgia, chronic fatigue syndrome (CFS), lupus, or other autoimmune and neurodegenerative diseases.
Prevention
Attached ticks should be removed promptly. Protective clothing includes a hat and long-sleeved shirts and long pants that are tucked into socks or boots. Light-colored clothing makes the tick more easily visible before it attaches itself. People should use special care in handling and allowing outdoor pets inside homes because they can bring ticks into the house.
Tick Removal
Many urban legends exist about the proper and effective method to remove a tick, however it is generally agreed that the most effective method is to pull it straight out with tweezers. Data have demonstrated that prompt removal of an infected tick, within approximately 36 hours, reduces the risk of transmission to nearly zero; however the small size of the tick, especially in the nymph stage, may make detection difficult.
Treatment
Antibiotics are the primary treatment for Lyme disease; the most appropriate antibiotic treatment depends upon the patient and the stage of the disease. The antibiotics of choice are doxycycline (in adults), amoxicillin (in children), and ceftriaxone. Alternative choices are cefuroxime and cefotaxime. Macrolide antibiotics have limited efficacy when used alone. Physicians who treat chronic Lyme disease have noted that combining a macrolide antibiotic such as clarithromycin (biaxin) with hydroxychloroquine (plaquenil) is especially effective in treatment of chronic Lyme disease. It is thought that the hydroxychloroquine raises the pH of intracellular acidic vacuoles in which B. burgdorferi may reside; raising the pH is thought to activate the macrolide antibiotic, allowing it to inhibit protein synthesis by the spirochete.
In later stages, the bacteria disseminate throughout the body and may cross the blood-brain barrier, making the infection more difficult to treat. Late diagnosed Lyme is treated with oral or IV antibiotics, frequently ceftriaxone for a minimum of four weeks. Minocycline is also indicated for neuroborreliosis for its ability to cross the blood-brain barrier.
Antibiotic treatment is the central pillar in the management of Lyme disease. In the late stages of borreliosis, symptoms may persist despite extensive and repeated antibiotic treatment. Lyme arthritis which is antibiotic resistant may be treated with hydroxychloroquine or methotrexate. Experimental data are consensual on the deleterious consequences of systemic corticosteroid therapy. Corticosteroids are not indicated in Lyme disease.
Antibiotic refractory patients with neuropathic pain responded well to gabapentin monotherapy with residual pain after intravenous ceftriaxone treatment in a pilot study. The immunomodulating, neuroprotective and anti-inflammatory potential of minocycline may be helpful in late/chronic Lyme disease with neurological or other inflammatory manifestations. Minocycline is used in other neurodegenerative and inflammatory disorders such as multiple sclerosis, Parkinson’s disease, Huntington’s disease, rheumatoid arthritis (RA) and ALS.
A number of other alternative therapies have been suggested, though clinical trials have not been conducted. For example, the use of hyperbaric oxygen therapy (which is used conventionally to treat a number of other conditions), as an adjunct to antibiotics for Lyme has been discussed. Though there are no published data from clinical trials to support its use, preliminary results using a mouse model suggest its effectiveness against B. burgdorferi both in vitro and in vivo. Anecdotal clinical research has shown potential for the antifungal azole medications such as diflucan in the treatment of Lyme, but has yet to be repeated in a controlled study or postulated a developed hypothetical model for its use.
Alternative medicine approaches include bee venom because it contains the peptide melittin, which has been shown to exert inhibitory effects on Lyme bacteria in vitro; no clinical trials of this treatment have been carried out, however.
For early cases, prompt treatment is usually curative. However, the severity and treatment of Lyme disease may be complicated due to late diagnosis, failure of antibiotic treatment, and simultaneous infection with other tick-borne diseases (co-infections) including ehrlichiosis, babesiosis, and bartonella, and immune suppression in the patient.
A meta-analysis published in 2005 found that some patients with Lyme disease have fatigue, joint or muscle pain, and neurocognitive symptoms persisting for years despite antibiotic treatment. Patients with late stage Lyme disease have been shown to experience a level of physical disability equivalent to that seen in congestive heart failure. In rare cases, Lyme disease can be fatal.
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