Lyme Disease

Basics

Description

Multisystem illness caused by the spirochete Borrelia burgdorferi, carried by the deer tick

Epidemiology

  • Can affect people of all ages, but 1/3 to 1/2 of all cases occur in children and adolescents
  • Male/female ratio: 1:1 to 2:1
  • Onset most often in summer months
  • Although Lyme disease can be found anywhere, the majority of the cases in the United States are found in Southern New England and the mid-Atlantic states. It is also seen frequently in California, Minnesota, and Wisconsin.
  • The most common tick-borne disease in the United States, with incidence in 2015 of 8.9/100,000.
    • However, incidence varies significantly in different parts of the country and 95% of all cases reported were found in 14 states: Connecticut, Delaware, Maine, Maryland, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Virginia.
    • Outside of those states, Lyme disease remains rare.

Risk Factors

Genetics

Chronic Lyme arthritis seems to be associated with increased incidence of HLA-DR4 and less so with HLA-DR2.

Pathophysiology

  • B. burgdorferi is injected into skin with saliva during bite of Ixodes tick.
  • Spirochetes first migrate within skin, forming the typical rash, erythema migrans.
  • Spirochetes then spread hematogenously to other organs, including heart, joints, and nervous system.

Etiology

The tick-borne spirochete B. burgdorferi

Commonly Associated Conditions

The same ticks that transmit Lyme disease can also transmit Ehrlichia and Babesia, so infections with those spirochetes can occur simultaneously.

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