Lyme disease

Lyme disease is an infectious disease, first observed in and around Lyme, Connecticut in 1977. It is caused by the bacterium Borrelia burgdorferi, which is transmitted to humans by the bite of infected deer ticks. 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. 

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 20 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, false positives and false negatives are common and the two tests are not always in agreement. 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. 

Prevention

Lyme disease infection can be prevented by avoiding heavily wooded areas, where ticks may live in the moist, thick underbrush. If such places cannot be avoided, prevention can also be achieved 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, since the tick usually must be attached to the skin for at least 36 hours before the Borrelia burgdorferi bacteria is transmitted, removing the tick immediately when found may prevent infection. 

Treatment

Treatment of Lyme disease usually consists of a course of antibiotics. With the chronic late-stage form of the disease, it may be necessary to continue antibiotic treatment for months or years.