Lyme Disease

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Lyme disease was first identified by researchers in 1975 after large numbers of children in Lyme, Conn., and two neighboring towns were found to have unexplained arthritis. After determining that the children played in wooded areas populated by deer and that symptoms usually started during the height of tick season, the researchers were able to trace the condition to an infection transmitted from deer tick bites. The deer ticks were found to carry Borrelia burgdorderi, a spiral-shaped bacteria that can cause a generalized infection, resulting in a wide range of symptoms.

Adult deer ticks usually live on white-tailed deer, though in their infant stages they prefer smaller animals like squirrels and mice. These deer ticks spread Lyme disease through their bites. Larger "wood ticks" and "dog ticks" have not been found to carry Lyme bacteria.

Lyme disease has been increasing in the Northeast as the deer population has grown and more suburban developments have been built in woodsy areas populated by deer. The condition has been reported in nearly all states, although most cases are concentrated in states in the coastal Northeast and mid-Atlantic region, Wisconsin, Minnesota, and northern California. Lyme disease also has been found in Asia, Europe, and most recently in South America. On average, only 1 percent of deer ticks carry Lyme, but in some areas more than half of ticks carry the bacterium.

About 20,000 cases of Lyme disease are reported to the Centers for Disease Control and Prevention every year. Typical symptoms include:

  • fever
  • headaches
  • fatigue
  • a characteristic oval-shaped skin rash called erythema migrans
  • If left untreated, infection can spread to the joints, heart, and nervous system. About 10 to 20 percent of untreated individuals will go on to develop chronic arthritis.

    Lyme disease is diagnosed based on symptoms, physical findings (i.e., rash), and the possibility of exposure to infected ticks. Laboratory testing is helpful in the later stages of the disease. Most cases of Lyme disease can be treated successfully with a relatively short course of antibiotics. Ways to prevent infections include using insect repellents, removing ticks promptly, and applying landscaping techniques that include pest management.

    This section contains more information on:

    • Causes
    • Risk factors
    • Links
    • Causes

      The Lyme disease bacterium, Borrelia burdorferi, is transmitted from animal to person through the bites of certain kinds of ticks. In the Northeast and north-central United States, the blacklegged tick, commonly known as the deer tick, transmits Lyme disease. In the Pacific coastal states, the disease is spread by the western blacklegged tick. Since even adult deer ticks are only about 1/8 inch long—much smaller than the more common dog ticks—they can easily feed off a person undetected. In fact, many people who develop Lyme don't recall having a tick bite. Other tick species in the United States have not been found to carry the Lyme bacterium.

      Although the ticks feed on deer, these animals don't become infected with Lyme disease, but they are important for the transmission of Lyme disease since they carry the ticks from place to place. Most cases of human illness occur in the late spring, summer, and early fall, when the tiny nymph ticks feed most actively and when human outdoor activity is greatest. However, infections can occur throughout the year.

      Risk factors

      Living in areas populated by deer increases the risk of getting Lyme disease. There is no evidence that Lyme disease can be transmitted from person to person. For instance, you can't get infected by touching, kissing, or having sex with a person who has Lyme disease.

      Pregnant women should be very careful to avoid ticks because the infection can be transferred to the fetus and can lead to miscarriage or stillbirth. However, no negative effects on the fetus have been found when the mother receives antibiotic treatment for Lyme. There are no reports of Lyme disease transmission through breast milk.

      Although no cases of Lyme disease have been linked to blood transfusion, research has shown that the bacteria can live in blood that is stored for transfusion. For this reason, the American Red Cross and Food and Drug Administration ask that people ill with Lyme disease avoid donating blood. Those who have been treated with antibiotics and have recovered from Lyme can donate blood beginning a year after the last dose of antibiotics was taken.

      Dogs and cats can get Lyme disease, but there's no evidence that they spread the disease to their owners. These pets can, however, bring infected ticks into the home and yard, so pet owners should consider using tick control products on their animals. Lyme disease can't be transmitted from eating deer meat, but hunters should be aware that they might come in close contact with infected ticks while handling the deer after the hunt.


      More information on Lyme disease is available at these websites recommended by the U.S.News & World Report library:

      NIH Medline Database on Lyme Disease

      This is a clearinghouse of information from various websites on treatment, symptoms, diagnosis, and clinical trials, as well as special issues related to Lyme disease. Lyme disease information from the Centers for Disease Control and Prevention

      The CDC shows photos of Lyme skin rashes and deer ticks and gives guidance on traveling to Lyme-infested areas. American Lyme Disease Foundation

      The foundation has information in English and Spanish on Lyme disease, including a section on frequently asked questions. National Guideline Clearinghouse

      This government site presents evidence-based guidelines for the management of Lyme disease. Last reviewed on 10/03/2007

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