What is Lyme Disease

Lyme disease is caused by a bacterial infection transmitted by ticks, and the individual’s subsequent immune reaction to the infection. It is characterised by arthritis, neurological and cardiac complications, with a characteristic rash that spreads from the initial tick bite.

Statistics on Lyme Disease

The incidence of Lyme disease is not well documented, and it is likely that figures are somewhat higher than those reported. It is the most common vector borne (transmitted by another species) disease in the United States.

Risk Factors for Lyme Disease

Lyme disease is caused by the spirochete Borrelia burgdorferi, which is transmitted by the Ixodes tick. The spirochete can be transmitted during the blood meal of an infected tick. Studies have indicated that transmission requires a minimum of 24 to 48 hours of tick attachment. The ticks are carried by field mice, voles, sheep and horses, and have a wide distribution throughout the United States, United Kingdom and Europe.
They are especially numerous in wooded or long grassed areas, hence farmers, forestry workers and bush walkers tend to be at highest risk. Activity is seasonal, with peak periods in late spring, early summer, and autumn.

Progression of Lyme Disease

Traditionally the progression of Lyme disease is divided into 3 stages; however this is somewhat artificial as progression from an early to later stage is not inevitable, even in the absence of antibiotic treatment. The earlist, and in most cases only, clinical feature of Lyme disease is the classic erythema migrans rash – an area of redness migrating outwards from the site of a tick bite, which may have occurred anytime from 2 to 40 days previously.
The second stage of Lyme disease occurs some weeks to months after initial infection and results from the spread to more distant sites via the bloodstream and lymph system. Many organs and tissues are potential targets, especially the skin, nervous system, heart, and joints. Clinical features depend on the affected system and the severity of damage. Patients may complain of a flu-like illness, with sweats and muscle aches.

How is Lyme Disease Diagnosed?

Lyme disease should always be considered if there is a history of exposure to ticks. A negative history of tick bite does not exclude the disease. Inquiry should be made into work, travel and recreational exposure and pets.
Tests may be performed on blood or spinal fluid. The organism may be grown in the laboratory over 3-4 weeks. DNA detection is also possible.

Prognosis of Lyme Disease

Prognosis is generally excellent, and only a few fatalities have been reported. Even without treatment, recurrent episodes of Lyme arthritis tend to resolve over a period of years. Children tend to have a better chance of complete recovery than adults.

How is Lyme Disease Treated?

Treatment for Lyme disease is with antibiotics. Measures to reduce tick exposure, such as keeping skin covered and using insect repellent should be considered.

Lyme Disease References

[1] Connell S. Fortnightly review: Lyme disease in the United Kingdom. BMJ 1995;310:303-308.
[2] Meyerhoff J. Lyme Disease. eMedicine 2004.
[online @ http://www.emedicine.com/med/topic1346.htm] [3] Occi J, Macgregor R. Identifying the Vector of Lyme Disease. Am F Phys, 2004.
[online @ http://www.aafp.org/afp/20040415/1935.html] [4] Sleigh J, Timbury M. Notes on Medical Bacteriology 5th ed (1998). Churchhill Livingstone, Singapore.