Lyme disease is an infectious disease, caused by the Borrelia spirochete, a gram-negative microorganism.

Contents

1 History 2 Cause 3 Vector 4 Symptoms 4.1 Acute (early) symptoms 4.2 Chronic (late) symptoms 5 Diagnosis 6 Prognosis 7 Prevention 8 Treatment 9 External links

History

Lyme Disease is so named because it is generally believed to have first been observed in and around Lyme, Connecticut in 1977. Before 1977 the Borrelia infection was also called tick-borne meningopolyneuritis, Garin-Bujadoux, Bannwarth Syndrome or sheep tick fever.

The disease was first documented as a skin rash in Europe in 1883. Over the years, researchers there identified additional features of the disease, including an unidentified bacteria that was treatable with penicillin, the role of the Ixodes tick as its carrier, and symptoms that included not only the rash but additional ones that affected the nervous system.

Researchers in the US have been aware of tick infections since the early 1900s. For example, an infection called tick relapsing fever was reported in 1905, and the wood tick, which carries an agent that causes Rocky Mountain spotted fever, was identified soon after.

The full syndrome now known as Lyme disease, however, was not identified until a cluster of cases thought to be juvenile rheumatoid arthritis occurred in three towns in southeastern Connecticut, in the United States. Two of these towns, Lyme and Old Lyme, gave the disease its popular name.

In 1982, the infecting agent was first isolated by Willy Burgdorfer, a scientist at the National Institute of Health who specialized in the study of spirochete microorganisms. This gave this spirochete its name, Borrelia burgdorferi.

Cause

It is caused by the bacterium Borrelia, which has over thirty known genomic strains but is usually cultured as Borrelia burgdorferi, Borrelia afzelii and Borellia garinii. The disease has been found to be transmitted to humans by the bite of infected ticks. Not all ticks can transmit the disease.

Lyme disease also incoporates the transmissions of tick borne co-infections including Bartonella, Babesia, Ehrlichia, Rickettsia and Mycoplasma.

Vector

Borrelia is found in mammal blood upon infection and is transmitted by the tick "spitome" or saliva. The spirochete is transfered when the tick feeds on a desirable host. Roughly 17,000 infections are reported in the United States each year. The illness often goes unreported and the real numbers are probably ten-fold higher.

The wood or black-legged deer tick (Ixodes rinicus) has been identified as the key to its spread. This condition had been described in medical literature dating back to the turn of the century but little to no research had been done until Lyme Disease was reintroduced to the medical field in the late 1970's.

The number of cases, as well as endemic regions in the United States, have been increasing. Lyme disease is reported in nearly every state in the U.S. There are concentrated areas in the northeast, mid-Atlantic states, Wisconsin, Minnesota, and Northern California. Lyme disease is endemic to Europe and Asia.

Lyme disease has been proven to be congenially passed from an infected mother to fetus through the placenta during pregancy. There is some anecdotal, largely unconfirmed evidence of sexual-transmission.

Symptoms

Lyme Disease has many symptoms, but skin symptoms, arthritis and various neurological symptoms are usually present. Coventional therapy is with antibiotics.

Acute (early) symptoms

• "bull's-eye" rash (erythema migrans - a circle or ring of inflamed skin surrounding the initial tick bite) or papular rash.
• fever
• malaise
• fatigue
• headache
• muscle and joint aches
• sore throat
• sinus infection

The incubation period from infection to the onset of symptoms is usually 1-2 weeks, but can be as long as one month. However, it is possible for an infected person to display no symptoms, or display only one or two symptoms, which can make diagnosis difficult.

Chronic (late) symptoms

• meningitis
• neuropathy - numbness, tingling, burning
• muscle and joint aches
• tremor, twitches
• Bell's palsy
• pain
• immune supression
• myalgia
• fatigue
• hallucinations
• short-term memory loss

The late symptoms of Lyme disease can appear months to years from infection. Left untreated, Lyme disease can cause chronic disability, but is rarely fatal. Chronic cases have been known to linger for years before a definitive diagnosis. Lyme Disease has been misdiagnosed as Chronic-Fatigue Syndrome, Multiple Sclerosis, Rheumatoid arthritis and a host of other autoimmune and neurological diseases.

Diagnosis

The most reliable method of diagnosing Lyme disease is a clinical exam supported by laboratory tests. In cases where the "bull's eye" rash is present in conjunction with a fever or the patient saw the tick, treatment can begin without any further tests.

The laboratory tests available are the Western blot and ELISA, but neither is a reliable indicator: test results vary between labs and within the same lab, sero-negative results are frequent. Polymerase chain reaction (PCR) tests for Lyme disease may also be available to the patient. A PCR test attempts to detect the genetic material (DNA) of the Lyme disease spirochete, where as the Western blot and ELISA tests look for antibodies to the organism. PCR tests are also susceptible to false-positive results.

In cases of chronic Lyme disease, diagnosis is often clinical and must take all factors into account (tick bite exposure, symptom history, etc..). Positive diagnosis will continue to be problematic until a more reliable test is developed.

Prognosis

The severity and treatment of Lyme disease can be complicated by simultaneous infection with other tick-borne diseases, also known as coinfections, bacterial load and immune suppression in the patient.

Prevention

The probability of contracting Lyme disease can be reduced by avoiding areas in which ticks are found. If such places cannot be avoided, exposure to Lyme disease can be reduced by:

• applying insect repellent to exposed skin, especially those containing DEET. Permethrin can also be applied to clothing,
• wearing light-coloured clothing so that ticks can be located easily and removed,
• wearing long sleeves and pants and tucking pant bottoms into the tops of socks.

In addition, tick removal immediately when found may prevent infection. It is an excellent idea to preserve the tick and have it tested for Lyme disease if the bite occured in an endemic area.

Treatment

Treatment of acute Lyme disease usually consists of a one month course of antibiotics. Patients with coinfections may need prolonged treatment. With the chronic late-stage form of the disease, it may be necessary to continue antibiotic treatment for months or years. In some cases immunomodulating drugs are necessary.

External links

• International Lyme and Associated Diseases Society (http://www.ilads.org)
• Lyme Disease: The Facts, The Challenge (http://www.niaid.nih.gov/publications/lyme/niaid%20lymedisbookf2.pdf)
• National Institute of Allergy and Infectious Diseases: Lyme Disease (http://www.niaid.nih.gov/dmid/lyme/)
• The CDC on Lyme Disease (http://www.cdc.gov/ncidod/dvbid/lyme/who_cc/)
• Official interactive tutorial on lyme disease (http://www.nlm.nih.gov/medlineplus/tutorials/lymedisease/id239101.html)
• The Lyme Disease Network (http://lymenet.org/)
• The American Lyme Disease Foundation (http://www.aldf.com/)
• The Clompexities of Lyme Disease - A Microbiology Tutorial (http://www.canlyme.com/tom.html)
• Molecular Genetics of the Lyme Disease Spirochete: Teaching a New Bug Old Tricks (http://videocast.nih.gov/ram/dss040502.ram)
• The Elucidation Of Lyme Arthritis (http://videocast.nih.gov/ram/wals110399.ram)
• Lyme Disease (http://www.surviveoutdoors.com/reference/lyme.asp)
• Lyme Disease Pictures (http://www.surviveoutdoors.com/emergency/tickbites.asp)
• Lyme Disease Slide Show (http://www.lymepa.org/html/dr__j__burrascano_may_3__2003_0.html)
• The Dirty Truth about Lyme Disease (http://www.angelfire.com/biz/romarkaraoke/Lymetruth.html)

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