Description

• A multisystem infection caused by the spirochetes of Borrelia strains, which is transmitted primarily by ixodid ticks:
  • I. scapularis (deer ticks) in the New England and Great Lakes areas
  • I. pacificus in the West, also known as black-legged ticks and Western black-legged ticks
  • I. ricinus in Europe
  • I. persuladas in Asia and Russia
• Early localized Lyme disease includes a characteristic expanding skin rash (erythema migrans) (70%) and constitutional flulike symptoms.
• Disseminated Lyme disease may present with involvement of ≥1 organ systems. Neurologic, cardiac, and pauciarticular arthritis are most common.
• Post-Lyme disease syndrome involves arthritis (50%) and chronic neurologic syndromes.
• System(s) affected: Hemic/Lymphatic/Immunologic; Musculoskeletal; Skin/Exocrine; Cardiac; Neurologic
• Synonym(s): Lyme arthritis; Lyme borreliosis

Epidemiology

• Most cases of Lyme disease in the US occur in southern New England; southeastern New York; New Jersey; eastern Pennsylvania; eastern Maryland; and parts of Minnesota, Wisconsin, and Michigan (1)[B].
• In states where Lyme disease is endemic, the incidence is 0.5 per 1,000, but can be substantially higher in local areas (2)[B]. Cases have been reported from all 50 states.

• The most common tickborne infection in the US and Europe
• Annually Europe: 65,500; North America: > 20,000; Asia: 3,500; North Africa: 10 (3)
• Predominant age: Can occur in all ages, but most common in children ages 5–14 and in the 55–70-year age group
• Predominant sex: Male > Female in the US

Risk Factors

• Exposure in tick-infested area; most common April–November
• Those who reside or are employed in areas where ticks are found are at increased risk.
• Ixodid ticks are commonly found on deer. Hunters may be at an increased risk.

Genetics
Human leukocyte antigen: Haplotype DR4 or DR2 may be more susceptible to prolonged arthritis.

General Prevention

• Prevention of infection is possible by careful exam of skin for ticks after outdoor activities.
• The prompt removal of ticks may limit transmission.
• Clothing that covers the ankles should be worn in endemic areas, and the use of insect repellants containing DEET is recommended.
• No vaccine is currently available.
• Prophylactic treatment with 1 dose of 200 mg of doxycycline within 72 hours of a tick bite in highly endemic areas has been suggested. (This is contraindicated in pregnancy and children; no prophylactic agent is approved for these groups.) (4)[A]

Etiology

• Infection with spirochete B. burgdorferi in the US, or B. afzelii or B. garinii in Europe, transmitted by the bite of ixodid ticks
• Primary animal reservoir is the white-footed mouse.

Commonly Associated Conditions

Southern tick–associated rash illness may be mistaken for Lyme disease. It is seen in the southeastern and south central US, and is associated with the bite of the Lone Star tick, Amblyomma americanum.