Lyme disease

background

Lyme disease is an infection caused by Borrelia burgdorferi. B. burgdorferi is a bacterium that is carried by a group of closely related species of ticks known as Lxodes. An infected tick can transmit the bacteria to humans and animals through its bite. The bacteria enter the body at the spot where the tick has bitten.
Ticks in the species of Lxodes, including deer ticks (also called black-legged ticks) and western black-legged ticks, are much smaller than the common dog or cattle ticks, and attach to any part of the body, most often to moist or hairy areas such as the groin, armpits, and scalp. The deer tick (Lxodes scapularis) is the primary carrier of Lyme disease in eastern North America.
If not treated, the bacteria travel through the bloodstream and attach to various body tissues. This may cause a number of symptoms, some of which are severe. Lyme disease is an inflammatory disorder, affecting joints, the nervous system, the heart, and the skin.
Symptoms include joint pain and flu-like signs, such as a fever, aches, and chills. Pain in the muscles and joints is common early on in Lyme disease. Many individuals experience spontaneous improvement of the pain, or a diminishment of it over time. In about 20% of people with untreated Lyme disease, arthritis (inflammation) of the joints can become chronic.
Severe symptoms include neurological (nerve) damage, including memory loss, difficulty concentrating, and changes in mood or sleep habits.
This disease has been recognized since November 1975 when 12 children of a small rural community, Old Lyme, Connecticut, were diagnosed with juvenile rheumatoid arthritis. Nearby several other people also reported a similar type of arthritis that came on suddenly. Research was done and 51 individuals were found to have developed the same disorder in a small geographical area and at the same time of the year. Most had brief attacks of pain and swelling involving a few large joints, and many reported having noticed a peculiar, expanding, red skin area several weeks before the joint pain and skin redness.
Lyme disease is a rapidly emerging infectious disease. The exact number of people affected by Lyme disease is not known. The U.S. Centers for Disease Control and Prevention (CDC) reported 23,305 cases of Lyme disease in the United States in 2005. Most occurred in the coastal northeast, the Mid-Atlantic States, Wisconsin, Minnesota, and northern California.
There are many factors contributing to the rise of Lyme disease in humans: an increase in the tick population (partially due to climate warming) and the expansion of suburbs into formerly wooded areas, which increases people's exposure to infected ticks. Because there are more and more people these days engaging in outdoor activities such as hiking, hunting, and climbing, more and more individuals are exposed to ticks, thereby increasing the incidence of Lyme disease. These people more frequently encounter deer or may be in areas where deer have been.
Most cases begin in the summer. In areas that have mild winters, the pattern is less seasonally specific.
If diagnosed and treated early with antibiotics, Lyme disease is almost always readily cured. However, the virus may lie dormant in the body for years and reappear.

Related Terms

Arrhythmias, B. burgdorferi, Bell's palsy, black-legged ticks, Borrelia burgdorferi, carditis, deer ticks, DEET, ELISA, enzyme-linked immunosorbent assay, erythema migrans, fibromyalgia, hepatitis, Lxodes, Lxodes scapularis, magnetic resonance imaging, meningitis, meta-N,N-diethyl toluamide, MRI, neurological, non-steroidal anti-inflammatory drugs, NSAID, palpitations, paralysis, PCR, permethrin, polymerase chain reaction, western black-legged ticks, Western blot.

stages

There are three separate stages of Lyme disease. Each has different symptoms.
Localized early disease stage: The onset of Lyme disease is called the localized early disease stage. If an individual is infected with Lyme disease, they may get a skin rash at the site of a tick bite. Common bite locations are the groin, the buttocks, behind the knee, or in the armpit. The rash may appear anywhere from a few days to a month after the tick has bitten. The bite site may feel hot to the touch and is usually red around the outside with a clear centre (called a bullseye). Beginning as a small area, the bite site expands slowly in size over several days and is usually not painful. Many individuals do not realize they have been bitten by a tick, and about one-third of people do not develop this rash.
Secondary stage: The secondary stage begins within several days of the appearance of the skin lesion, and many individuals develop symptoms and evidence of more widespread infection. There may be a vague feeling of discomfort or uneasiness, sluggishness or fatigue, headaches, and fever and chills. Aching joints and muscles and skin sores or rashes on various parts of the body may be present.
Third stage: About 20% of people with Lyme disease go into remission (temporary absence of disease) after the secondary stage has passed. Most individuals, however, will move into the third stage of the disease. In the third stage, other health conditions that involve the heart, nervous system, and joints can develop. The third stage may develop weeks, months, or rarely, years after the initial infection.
Carditis, or inflammation of the heart, develops in fewer than 10% of people with untreated Lyme disease. Initial symptoms can include rapid beating of the heart (palpitations or arrhythmias) or unexplained fainting. This condition may pass without medical intervention, but it sometimes requires medical treatment.
If the nervous system becomes inflamed, headaches, irritability, sensitivity to bright light, and lethargy can be experienced. In about 15% of people, meningitis (inflammation of the protective membranes covering the brain) may occur a few weeks after the initial rash.
Other symptoms indicating involvement of the disease in the brain and the nerves may occur months to years after the disease onset. Nerves in the limbs or around the head may be affected, and individuals could experience muscle weakness, paralysis, or loss of sensation. Bell's palsy, a condition that results in weakness or paralysis of the facial muscles, can also occur. If the disease affects the brain, short-term memory loss, difficulty concentrating, chronic fatigue, headaches, and sleep disturbance can occur. In rare cases, the disease can cause seizures and lesions on the spinal cord.
Most individuals with advanced Lyme disease experience attacks of arthritis involving one or only a few joints. Usually it is the large joints, such as the knees, that are affected. Involvement of many joints is uncommon. Attacks can last a few days to a few weeks. In children, the arthritis is usually much milder. Despite the ongoing inflammation, it is unusual for it to result in damage to the cartilage and bone, as may occur more commonly in other forms of arthritis. In comparison to rheumatoid arthritis, which affects both joints, Lyme disease can affect one or both joints.