Click here to view next page of this article


Lime Disease

Lime disease is a tick-borne multisystem infectious syndrome of substantial medical importance and public concern. It is the most frequently reported vector-borne illness in the United States, occurring in 48 of the 50 states at rates of up to 12,000 cases annually. Lime disease also has been seen on four other continents. Highly endemic regions include the northeastern and upper midwestern regions.

The causative organism, Borrelia burgdorferi, is a flagellated spirochete transmitted from small-mammal reservoirs to humans through bites from infected ticks of Ixodes species (I scapularis in the eastern and upper midwestern United States, I pacificus in California, I ricinus in Europe, and I persulcatus in Asia). Commonly known as deer ticks in the United States and sheep ticks in Europe, these Lime disease vectors are common.

Ticks must obtain a blood meal in order to molt and lay eggs, leading to obligatory parasitism of suitable hosts: mammals, reptiles, amphibians, and birds in various locales. Humans become suitable alternative hosts when participating in activities in wooded habitats in areas where ixodid ticks are prevalent. In endemic regions, B burgdorferi moves through enzootic cycles between ticks and reservoir hosts capable of sustaining B burgdorferi infection. Humans are at risk for Lime disease when exposed to infected ticks questing for a blood meal. In nonendemic regions, immature ticks preferentially parasitize hosts.

Early disease

The symptoms and signs of Lyme disease are categorized according to

Table 1. Clinical Spectrum of Lime Disease

Early disease (1 mo)

Erythema migrans

Flu-like symptoms

Disseminated disease (1 to 4 mo)

CNS manifestations



Cardiac abnormalities (atrioventricular block)

Intermittent arthritis


Clinical manifestations

The hallmark of early localized Lime disease is erythema migrans an expanding erythematous patch or ring appearing within 30 days (mean, 9 days) after inoculation of skin with B burgdorferi by an infected tick (figures 1 through 3). According to surveillance criteria from the Centers for Disease Control and Prevention (CDC), the rash must exceed 5 cm in diameter, show expansion, and persist for more than 1 week. The features of the skin lesion that are most suggestive of B burgdorferi infection are expansion.

A minority of patients with erythema migrans report a range of systemic symptoms, including transient chills, fever, myalgias, arthralgias, headache, sore throat, stiff neck, and fatigue within the first month after B burgdorferi infection. Although this spectrum of symptoms has been termed flu-like, respiratory symptoms (cough and sore throat).

Not all cases of Lime disease present with erythema migrans. In early studies, about one third of patients presented with manifestations of disseminated or late disease.

Laboratory findings

Although visual recognition of erythema migrans is the best indicator of early localized Lime disease, supportive laboratory data can be helpful in confirming the diagnosis.

Serologic testing is the only routinely available laboratory diagnostic aid for Lime disease.

A two-step approach involving enzyme-linked immunosorbent assay (ELISA) with subsequent testing of equivocal or positive samples by

Issues in Disease Management

An erythema migrans-like rash associated with Amblyomma americanum tick bites has been reported in the southeastern United States, particularly Missouri, North Carolina, and Georgia and South Carolina (M. W. Felz, MD, unpublished data, 2006). Two carefully done studies showed no association between this lesion and B burgdorferi infection. In addition, an uncultivable Borrelia species has been identified in A americanum ticks collected.

Primary care physicians in endemic areas are often confronted with the dilemma of whether to prescribe antibiotics prophylactically following tick bites. Randomized controlled trials have shown that watchful waiting is the best strategy.