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Lyme disease is an infectious disease, first observed in and around Lyme, Connecticut in 1977. It has many symptoms, but skin symptoms, arthritis and various neurological symptoms are usually present. Therapy is with antibiotics.

Cause

It is caused by the bacterium Borrelia burgdorferi, which is transmitted to humans by the bite of infected ticks.

Vector

The most common vector is the deer tick, but other ticks are capable of transmitting Lyme disease. The deer tick can be found on most continents and is particularly common in North-Eastern North America, the Rocky Mountains, the European Alps, temperate parts of Asia and Japan. There is some anecdotal, largely unconfirmed evidence of sexual-transmission and transmission via contaminated blood-supply.

Symptoms

Acute (early) symptoms

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

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
• numbness, tingling, burning
• muscle and joint aches
• tremor, twitches
• Bell's palsy
• pain
• 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 19 years before a definitive diagnosis.

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. In cases of chronic Lyme disease, diagnosis must take all factors into account (tick bite exposure, symptom history, etc..) and 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. These diseases include Babesiosis, Ehrlichiosis, and Bartonella (cat scratch fever).

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, removing the tick 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 Lyme disease usually consists of a 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.

External links

• International Lyme and Associated Diseases Society
• Lyme Disease: The Facts, The Challenge
• National Institute of Allergy and Infectious Diseases: Lyme Disease
• The CDC on Lyme Disease
• Official interactive tutorial on lyme disease
• The Lyme Disease Network
• The American Lyme Disease Foundation
• Molecular Genetics of the Lyme Disease Spirochete: Teaching a New Bug Old Tricks
• The Elucidation Of Lyme Arthritis
• Lyme Disease
• Lyme Disease Pictures

• Infectious diseases