Pediatric Lyme Disease 

Lyme disease is the most common tick-borne illness in the United States. Although erythema migrans (EM), the characteristic rash associated with Lyme disease, was initially described in 1921, Lyme disease was first formally described in the medical literature in 1976 following an outbreak of arthritis in Lyme, Connecticut. Since then, the number of reported cases has increased dramatically, likely as a result of increased awareness of clinicians and patients in endemic areas.

Go to Lyme Disease for complete information on this topic.

The spirochete Borrelia burgdorferi is introduced into the skin and spreads locally. The local spread leads to EM, a rash that is found in approximately two thirds of cases.

Over days to months, the spirochete may invade the blood stream, leading to disseminated disease. Dissemination to the skin can manifest as multiple EM. B burgdorferi can spread to any tissue but commonly affects the skin, eye, muscle, heart, and central nervous system. Arthritis is a characteristic manifestation of late disease and is caused by the persistence of organisms in the synovium. Some patients, particularly adults, appear to have persistent symptoms after adequate antimicrobial treatment, suggesting an autoimmune component to chronic symptoms.

Lyme disease is caused by B burgdorferi^[1] which is transmitted by ixodid tick species--primarily Ixodes scapularis, the common deer tick (see the images below).

The life cycle of ixodid ticks occurs over 2 years. The adult lays eggs in the spring, and the larvae emerge in the summer. The larvae feed on a wide variety of small animals (eg, the white-footed mouse) that serve as important reservoirs for B burgdorferi. The following spring, the larvae emerge as nymphs that likewise mainly feed on small animals. The nymphs molt into adults the following fall and spend the winter feeding on larger animals, most notably the white-tailed deer. Ticks can acquire B burgdorferi during any of the 3 life-cycle stages.

Lyme disease is passed to humans mostly by nymphs because (1) nymphs are more abundant than adult ticks during the months of greatest human outdoor activity and (2) nymphs are more difficult to detect because of their smaller size. The risk of transmission of B burgdorferi from an infected tick to a human depends on the length of exposure. It takes hours for the tick to attach fully, and experimental studies have indicated that nymphs must feed 36-48 hours and adults 48-72 hours to transmit B burgdorferi.

The number of reported cases has increased 101% from 9908 cases in 1992 to 19,931 cases in 2006. Incidence is highest in children aged 5-14 years. The 3 distinct regions in the United States are (1) the Northeast (from Massachusetts to Maryland), (2) the upper Midwest (especially Minnesota and Wisconsin), and (3) the West Coast (especially northern California).

Based on the life cycle of the tick in the United States, onset of illness is between May and October, with most cases presenting in June and July.

Lyme disease occurs throughout the world. B burgdorferi infection has been reported in Asian countries, including China, Korea, Japan, Indonesia, Nepal, and eastern Turkey.

In Europe, most Lyme disease is reported by Scandinavian countries, Germany, Austria, and Slovenia. In Europe, Lyme disease is primarily caused by Borrelia afzelii and Borrelia garinii, whose clinical manifestations differ somewhat from those of B burgdorferi. B garinii tends to disseminate less widely than B burgdorferi but is especially neurotropic and may cause encephalomyelitis. B afzelii often infects the skin only but may persist in that site, causing various cutaneous manifestations including acrodermatitis chronica atrophicans.

The prognosis for all stages of Lyme disease is generally excellent when patients are treated early with appropriate antibiotic regimens. For patients with chronic symptoms post infection, randomized controlled trials of extended antibiotic regimens have not shown any efficacy.

Symptoms of arthritis may persist for a few weeks beyond adequate therapy; therefore, retreatment usually is not necessary unless symptoms worsen or persist beyond 2 months. Some individuals with arthritis do have persistent symptoms after clearance of the infection. This phenomenon is most likely related to autoimmunity and is more prevalent among individuals with HLA-DR2, HLA-DR3, or HLA-DR4 allotypes.

Unfortunately, antibodies induced by the infection are not protective against further exposures to B burgdorferi; therefore, reinfection easily could be confused with a recurrence. Because antibodies may persist for years following an infection, repeat infection is a difficult diagnosis without specific signs of Lyme disease (eg, EM rash). Increasing titers after adequate treatment certainly raises suspicion of an active infection.

Primary care providers should educate parents and children who live in endemic areas about the risk of Lyme disease. Anticipatory guidance should focus on prevention measures and post–tick exposure counseling on watching for symptoms and signs of Lyme disease.

For patient education resources, see the Bites and Stings Center and Muscle Disorders Center, as well as Lyme Disease, Ticks, Chronic Fatigue Syndrome, and Chronic Pain.