Lyme disease

Abstract

Lyme disease, caused by the spirochete Borrelia burgdorferi, is the most common vector-borne disease in the United States. The clinical presentation varies depending on the stage of the illness: early disease includes erthyma migrans, early disseminated disease includes multiple erythema migrans, meningitis, cranial nerve palsies, and carditis; late disease is primarily arthritis. The symptoms and signs of infection resolve in most patients after treatment with appropriate antimicrobials for 2 to 4 weeks. Serologic testing should be used judiciously as it often results in misdiagnosis when performed on blood from patients with a low prior probability of disease and those with only nonspecific symptoms such as fatigue or arthralgia without objective signs of infection.

Figure 1

Borrellia burgdorferi, infective bacterium of Lyme disease. The spirochete is stained with Syto 9 and visualized with fluorescent microscopy. Courtesy of Sarojini Adusumilli.

Figure 2

Epidemiology of Lyme Disease. The distribution of disease corresponds to the distribution of the Ixodes ticks that transmit B. burgdorferi.

Figure 3

Various stages of the life cycle of the deer tick Ixodes scapularis, the vector for Lyme disease in the northern United States. The larval stage is shown on the left, followed by the nymphal stage, the adult female, and the adult male on the right. Most infections are transmitted from ticks at the nymphal stage.

Figure 4

A comparison of the deer tick Ixodes scapularis, on the left, with the dog tick Dermacentor variabilis, on the right. Typically, dog ticks are much larger than deer ticks.

Figure 5

Two-year lifecycle of Ixodid ticks. Larvae hatch in the summer when they may feed on a small mammal infected with B. burgdorferi. The larvae survive the winter and emerge the following spring as nymphs, when they are most likely to transmit infection. The nymphs molt to become adults in the fall, attach to large animals during the winter, and the females lay eggs the following spring. (CDC Open access photo)

Figure 6

The white footed mouse (Peromyscus leucopus) is a reservoir for Ixodes scapularis. Note the large numbers of ticks attached to this mouse.

Figure 7

An engorged Ixodid scapularis tick. Ticks become engorged after 48-72 hours. Ticks removed prior to this time, before they become engorged, rarely transmit Lyme disease.

Figure 8

Erythema migrans. This rash is the characteristic lesion of early Lyme disease. It may be appear as a target-like lesion with central clearing or may be erythematous throughout.

Figure 9

Prolonged PR interval from Lyme carditis. This EKG is was performed on a 9 yr old child from a Lyme endemic area with known tick exposures who presented with a history of fever, flu-like symptoms, and syncope. His PR interval (shown by the arrow) was 0.548 (nl 0.12-0.2) consistent with first degree heart block. He was admitted to the hospital and placed on ceftriaxone therapy. His symptoms improved after three days and he was discharged home on doxycycline to complete 21 days of antimicrobial therapy.

Figure 10

IgG immunoblot used to aid in the diagnosis of Lyme disease. Immunoblots are indicated after a positive ELISA from a patient with a clinical syndrome consistent with Lyme disease. The criteria for a positive IgG immunoblot are the presence of 5 bands. In patients with erythema migrans, the immunoblot can initially be negative prior to the development of antibodies against B.burgdorferi.