Lyme Disease
Overview
Lyme disease is a progressive, systemic illness that is caused by bacteria (Borrelia burgdorferi) and is usually transmitted by the bite of an infected deer tick. Infection may result in flu-like symptoms (e.g., malaise, fever, headache, fatigue, muscle pain) and the characteristic "bull's eye" rash. If left untreated, it may cause arthritis and affect the heart and central nervous system. Lyme disease is treated with antibiotics.
Incidence and Prevalence According to the Centers for Disease Control and Prevention (CDC), more than 23,000 cases of Lyme disease occur each year in the United States. It is endemic (prevalent) throughout the wooded coastal regions of the Northeast, the Great Lakes, and the Pacific Northwest. In the Northeast and Great Lakes regions, the disease is more prevalent from May to August. In the Pacific Northwest, it is more prevalent from January to May.
Causes and Risk Factors
Lyme disease is caused by infection with Borrelia burgdorferi bacteria. In the Northeast and North Central United States, the deer tick (Ioxodes scapularis) is responsible for transmission and in the Northwest, the western black-legged tick (Ioxodes pacificus) is the carrier.
The ticks that cause Lyme disease are very small. They live in wooded areas, low-growing grasslands near seashores, areas overgrown with brush, and in yards. The adult ticks are black or reddish and feed on blood by attaching themselves to a host.
The risk for contracting Lyme disease in the United States is highest in the coastal region of southern New England, the mid-Atlantic, and the Great Lakes. During the summer months, people who live or work outdoors (e.g., clearing brush, forestry, landscaping) in these areas are especially at risk. Ticks can also come into contact with people when they attach themselves to pets.
Outdoor activities that increase the risk for tick bite and infection include the following:
- Camping
- Fishing
- Gardening
- Hiking
- Hunting
- Picnicking
Signs and Symptoms
Lyme disease may be asymptomatic or may produce symptoms that develop in three stages. The first stage causes flu-like symptoms (e.g., fever, headache, malaise, muscle pain) and the characteristic "bull's eye" rash, typically within 7 to 14 days of infection. These symptoms often resolve without treatment.
The rash begins as a red area at the site of the tick bite and gradually expands, often with central clearing, which produces the bull's eye. It can last from a few hours to several weeks and varies in size. Other types of rash have been noted, some of which resemble hives, eczema, sunburn, poison ivy, and flea bites. Dark-skinned people may develop a rash that resembles a bruise.
The rash may itch, disappear, and then return weeks later. In some cases, a single bite can cause rash to occur on several areas of the body.
The second stage develops in approximately 10% of patients and occurs weeks to months after infection. The bacteria spread throughout the body via the bloodstream and the lymphatic system, causing arthritis, rash, and eye inflammation. Second stage Lyme disease may also affect the heart and the central nervous system. This stage also may resolve without treatment.
Third stage Lyme disease can develop months to years after infection. This stage affects the musculoskeletal, ophthalmologic, cardiovascular, and central nervous systems. Symptoms include the following:
- Blockage in the chambers of the heart (atrioventricular block)
- Brain dysfunction resulting in memory loss (encephalopathy)
- Damage to nerves in the head (cranial neuropathy)
- Inflammation of the brain and spinal cord (encephalomyelitis) or membranes surrounding the brain (meningitis)
- Inflammation of the cornea causing decreased vision and eye pain (keratitis)
- Inflammation of heart muscle (myocarditis) or the membrane that surrounds the heart (pericarditis)
- Inflammation of joints causing pain, swelling, and structural changes (arthritis)
- Multiple rashes
- Rapidly progressive motor neuron paralysis involving inflammation of several peripheral nerves (radiculoneuritis)
Diagnosis
Diagnosis of Lyme disease is made based on clinical symptoms and case history. In cases of early stage disease, known exposure, and symptoms that suggest later stage disease, laboratory testing may support a diagnosis.
Laboratory Tests First, enzyme-linked immunosorbent assay (ELISA) or immunofluorescent assay is performed on a blood sample to identify Borrelia burgdorferi and antibodies to the bacteria. If there is a positive result, it may be confirmed using the Western blot test, which can detect small amounts of antibodies.
Positive results may be seen years after a successfully treated infection or an infection that resolved on its own. A positive result does not necessarily indicate active infection.
Ticks can be tested for bacteria. The tick should be removed carefully with fine tweezers, grabbing it as close to the skin as possible, and placed in a clean container with a moistened cotton swab. Squeezing the tick or applying petroleum jelly, a burnt match, or alcohol can transmit the bacteria and should be avoided.
Treatment
Early stage Lyme disease is treated with a 3- to 4-week course of antibiotics (e.g., amoxicillin, doxycycline, ceftriaxone), administered orally. Advanced disease may require intravenous ceftriaxone or penicillin for 4 weeks or longer, treatment for progressive symptoms (e.g., arthritis, neuropathy), and additional courses of treatment.
In areas where Lyme disease is prevalent, people should seek medical treatment if they are bitten by a tick that tests positive for Borrelia burgdorferi bacteria and symptoms develop. Women who are pregnant should seek prompt medical attention because the disease can be transmitted to the fetus.
Prognosis
When Lyme disease is diagnosed in its early stage, most patients are successfully treated with antibiotics. Humans do not develop immunity to Lyme disease and reinfection is possible. The disease is rarely, if ever, fatal.
Prevention
To prevent Lyme disease, avoid grasslands and wooded areas where incidence of the disease is high. When outside in these areas, apply insect repellent containing DEET (n,n-diethyl-m toluamide) to exposed skin. Apply permethrin (kills ticks on contact) to clothes and avoid getting this substance on the skin because it is toxic.
Wearing long-sleeved shirts and pants tucked into boots may prevent ticks from reaching the skin. Light-colored clothing makes it easier to see ticks.
Check clothing and skin carefully, especially where clothing touches the skin (e.g., cuffs, underwear elastic). Shower after all outdoor activities; if a tick is on the skin but unattached, it may wash off.
Run the fingers gently over the skin. An attached tick feels like a small scab. The tick must be attached to a person for 2 to 3 days to pass on the infection, so removing it within 36 hours will significantly reduce the risk for Lyme disease.
Carefully examine these areas on the body:
- Behind the knees
- Between fingers and toes
- Ears (inside and behind)
- Hairline and top of the head
- Navel (belly button)
- Neck