LD has become the most common vector-borne disease in North America. The highest prevalence occurs in patients aged 2 to 15 years and 30 to 59 years. In the United States, most LD is localized to three highly endemic areas: (a) the Northeast (Maine to Maryland), (b) the Midwest (Minnesota and Wisconsin), and (c) the West (Northern California and Oregon).

LD or lyme borreliosis is caused by members of the genus Borrelia. B. burgdorferi is the only species causing disease in the United States. B. afzelii and B. garinii are the predominant species infecting humans in Europe and Asia. B. burgdorferi is the most arthritogenic of the three Borrelia species that result in human disease. Pathogenic Borrelia are carried and transmitted by the Ixodes ricinus complex of ticks. The clinical manifestations of LD vary based on the stage of infection. Infection is divided into three stages: early localized, early disseminated, and late chronic. Table 113.1 provides the clinical features at different stages.

Symptoms typically develop between 7 to 10 days after a tick bite, but ranges of 1 to 36 days have been reported. The most common manifestation in children is erythema migrans rash followed by arthritis, facial nerve palsy, carditis, and aseptic meningitis.

Lyme meningitis in children may be subtle and usually occurs without meningismus. The presentation typically involves less fever, when compared with viral meningitis. As mentioned previously, arthritis is a common symptom found in LD. This diagnosis should be considered in any patient with arthritis, especially if they live or have recently traveled to an endemic area. Early diagnosis is essential because untreated infection may lead to more advanced disease involving the heart, central nervous system, and joints.