Lyme disease

Lyme disease is a tick-borne infection.


Causes/associated factors
In North America, Lyme disease is caused by Borrelia burgdorferi (B burgdorferi), a bacterium found in small rodents and other mammals, such as the white-footed mouse and white-tailed deer. Ticks that feed on these animals may become infested and, in turn, transmit B. burgdorferi to other animals and people. The small deer tick and the western black-legged tick are the only ticks that have been found to carry the bacterium. They are about the size of a pinhead or poppy seed. They crawl, but they can't fly or jump. The more common wood tick, which is four times larger than the deer tick, is not associated with Lyme disease.
Lyme disease is most common in children under age 15 and adults age 30 and older. The disease has been reported in 49 states and the District of Columbia. (Only Montana has no reported cases.) Most cases in the United States are concentrated in the Northeast between Massachusetts and Maryland, in the upper Midwest (especially Minnesota and Wisconsin) and on the Pacific coast (especially northern California). Cases of Lyme disease peak in June and July, but are considered common from April to October. It's also possible to be infected with Lyme disease more than once.


Transmission
Lyme disease is not transmitted from person to person or through contact with an infected animal. Transmission often happens through a simple chain of events. Infected ticks attach themselves to animals, such as deer. The animals carry the ticks to vegetation, often in wooded areas. The ticks attach themselves to humans when people brush against the leaves and brush. Pets can also carry ticks into the home, where they can be transferred to humans. To contract Lyme disease, it is believed that an infected tick must be attached to your body for 36 to 48 hours. The incubation period (time from exposure until symptoms appear) for Lyme disease is usually seven to 14 days, but it can range from three to 32 days. Note: Other diseases can also be transmitted by ticks, and a single tick bite can transmit more than one tick-borne disease.

Signs/symptoms
The symptoms of Lyme disease typically develop in stages.
Early local symptoms
About 80 percent of people who have Lyme disease develop a rash within three to 32 days of exposure. (For children, the appearance of a rash is more variable.) At the site of the tick bite, a red spot gradually expands. It's often clear in the center, creating a "bull's eye" pattern, and may become 5 inches or more in diameter. The rash may vary in appearance, size or shape, however. It may be warm to the touch, but rarely itchy or painful.

Other early symptoms may include:

headache
fever
fatigue
muscle and joint pain
neck stiffness
swollen lymph nodes (small, round structures located throughout the body that help protect you from invasion of bacteria or other organisms)
In the early stage, symptoms may be constant or come and go. Sometimes, there are no symptoms at all. Without treatment, the disease may progress to the next stage.

Early generalized symptoms
Within three to five weeks after exposure, a similar but smaller rash may develop in other areas. The nervous system, musculoskeletal system and heart may be affected. Symptoms may include:

fatigue
fever
chills
headache
facial palsy (loss of sensation or ability to move or control movement, usually on one side of the face)
meningitis (inflammation of the membranes surrounding the brain or spinal cord)
muscle and joint pain (without swelling) that moves from one place to another
conjunctivitis (inflammation of the membrane that lines the eye)
rarely, heart block (when the electrical impulses that control heart rate travel slowly, intermittently or not at all, sometimes causing breathlessness, a feeling of exhaustion, or fainting or feeling faint)
rarely, myocarditis (inflammation of the heart muscle)
Late symptoms
Late symptoms may develop months or even years after infection, even if there were no earlier symptoms. This stage is often characterized by intermittent joint pain and swelling, usually in the knees and other large joints. There may also be central nervous system problems, usually a mild encephalopathy (any dysfunction of the brain; encephalopathy is often characterized by memory loss, personality changes, fatigue and sleep disturbance).


Diagnosis
Lyme disease is often difficult to diagnose. It can mimic other conditions, and there is no single test to confirm the diagnosis. Diagnosis is usually based on the combination of your symptoms, history of tick bites or exposure to tick-infested areas, and possibly blood test results. The doctor will do a physical exam and ask questions about your medical history. Clinical suspicion of Lyme disease may be confirmed with a series of blood tests that help determine whether the body has developed antibodies (compounds that neutralize or destroy foreign substances in the blood) against the bacteria that causes the disease. These tests may include:
enzyme-linked immunosorbent assay (ELISA)
immunofluorescence assay (IFA)
Western blot (WB) test (immunoblot test)
Blood tests are often not reliable until later in the disease, however. And even then, many people who have Lyme disease test negative. Sometimes people may test positive when they do not have Lyme disease because they have another disease that cross-reacts with the test. Antibiotic treatment early in the disease and certain medical conditions can also interfere with testing. The Centers for Disease Control and Prevention (CDC) currently recommends the ELISA or the IFA be done first. If the results are positive, then the WB is done. The diagnosis of Lyme disease is more certain if the WB is also positive.

New, more sensitive tests to diagnose Lyme disease are being developed.


Treatment
Tick bites by themselves do not require antibiotic treatment. The decision to treat with antibiotics is based on the individual circumstances and risks the tick bite presents. Lyme disease is treated with antibiotics such as amoxicillin, doxycycline or erythromycin. If youibiotic and whether it's given orally or intravenously depends on the stage and severity of the disease, as well as your age and other factors. Generally, the longer you've had the infection, the longer and more aggressive the treatment. Most people respond to antibiotics well. Sometimes, repeated courses of treatment are necessary.

Complications
If Lyme disease is untreated or improperly treated, it can lead to varying degrees of permanent nervous system, cardiac or joint damage (often involving the erosion of bone and cartilage -- dense connective tissue in the joints).

Pregnancy-specific information
Rarely, the organism that causes Lyme disease can be transferred to a fetus during pregnancy. Researchers have not determined that Lyme disease causes birth defects or pregnancy problems, but it is best to help prevent infection by avoiding tall grass and wooded areas where ticks can be found.
If you're pregnant and have active Lyme disease, you'll need antibiotics. Penicillin or erythromycin can be used, but doxycycline (commonly used to treat Lyme disease) is not recommended during pregnancy.

The effects of the Lyme disease vaccine during pregnancy have not been studied on animals or humans. Consult your doctor if you're considering the vaccine or any other medications.


Senior-specific information
Growing older is not a risk factor for Lyme disease.

Prevention
The U.S. Food and Drug Administration (FDA) approved a Lyme disease vaccine in 1998, but in February 2002 the manufacturer announced that it had stopped the production and distribution of the vaccine due to insufficient demand.
Here some general preventive measures to keep in mind.

Reduce the number of ticks near your home by removing leaves and clearing any brush or tall grass around your home and gardens.

Avoid tick-infested areas, especially in the spring and summer months.

Don't forget your pets! Speak with your veterinarian about medications to help keep pets free of ticks.

If you must be outside in areas where ticks are found, walk on the center of trails to avoid grass and brush. Cover as much of your body as possible -- wear socks, shoes (preferably boots), a hat and a long-sleeved shirt with a tight-fitting collar. Tuck in your shirt and tuck your pant legs into your socks. Wear light-colored clothing so that ticks can be spotted more easily.

When you're outdoors, it's also a good idea to use an insect repellent. Brands containing diethyl-toluamide (DEET) are most effective. They may be used on any exposed, intact areas of skin, but be cautious and follow the manufacturer's directions carefully. A 10 to 35 percent formula repellent is recommended for adults. Check with your doctor before using insect repellents if you're pregnant or breastfeeding.
The best approach is to use the lowest concentration of DEET effective for the amount of time spent outside:


30-percent DEET protects for six hours
24-percent protects for five hours
20-percent protects for four hours
6.65-percent protects for two hours
4.75-percent protects for an hour and a half

Even for children, products containing DEET are the most effective insect repellents. The safety of DEET does not appear to be related to the concentration in the repellent. There are no studies on skin absorption of DEET in children, but studies of similar substances suggest that absorption through the skin would not differ after age 2 months. Currently, 30-percent DEET is the maximum concentration recommended for infants and children over age 2 months. Again, the concentration of DEET used is based on the time the child is expected to be outside. Keep insect repellent out of the reach of children at all times.

You can also apply Permethrin, an EPA-approved insecticide that works to kill insects rather than repel them. Permethrin is not applied to your skin. Instead, it's applied to your clothing and shoes to kill ticks. The product retains its effectiveness for up to two weeks, despite as many as five launderings. The risk of adverse effects is low because Permethrin is not readily absorbed by the skin. Check with your doctor before using any insecticides if you're pregnant or breastfeeding.

Before going inside, check your hair and clothing for ticks. Also check any pets that have been outside with you. Once inside, do a full body exam, including the scalp. (It's important to do a daily full body exam whenever tick bites are a possibility, especially if you're camping outdoors or involved in prolonged outdoor activities.)

Also check any pets that have been outside with you for ticks. Ask your veterinarian about medications to help keep pets tick-free.

Shower promptly to remove any ticks that may not have attached to your body yet, and put your outdoor clothing in the dryer for 30 minutes to kill any undetected ticks.
A recent study suggested that Lyme disease may be prevented with a single dose of antibiotic given within 72 hours of a tick bite. The CDC does not recommend the routine use of antibiotics after tick bites. However, if you're bitten by a deer tick in an area where Lyme disease is prevalent, you may want to consult your doctor.

Tick removal
Prompt and complete tick removal can decrease your risk of contracting Lyme disease. If you find a tick, remove it with a pair of tweezers, if available, or a finger protected with a rubber glove, tissue or paper towel. Grasp the tick as close to the skin as possible and pull it out with slow, steady pressure. This will loosen the tick's feeding parts and allow it to be removed intact. Avoid twisting, jerking, squeezing or crushing the tick, and make sure you remove the entire tick. (Older methods of tick removal, such as using oil, petroleum jelly, a hot match or alcohol, are not as effective and may actually make it impossible for the tick to release itself from your skin).

If there is any question regarding the type of tick involved, you may want to keep the tick in a container (such as a covered jar or sealed plastic bag) to show your doctor. Freeze the container if possible -- it may preserve the bacteria in the tick. The characteristics of the tick may influence treatment choices, and tests may be done on the tick if you develop Lyme disease. After you've removed the tick, wash your hands and the affected area with soap and water, and call your doctor for further instructions. Remove any ticks found on pets and flush them down the toilet.