Lyme Disease
Robert S. Baltimore MD1
Eugene D. Shapiro MD1
1 Departments of Pediatrics and of Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT.
Introduction and Definitions
Lyme borreliosis (Lyme disease) is a systemic infection caused by a spirochete, Borrelia burgdoferi. It is the most common vector-borne disease in the United States.
Lyme disease was first described in Lyme, Connecticut (hence its name), where a cluster of children who had unexplained arthritis first were brought to medical attention by one of their parents. Investigation of this "epidemic" of arthritis led to the description of Lyme arthritis and ultimately to the discovery of its bacterial etiology. The clinical manifestations of Lyme borreliosis are protean; this, coupled with the practical difficulties of confirming the diagnosis in many patients, has led to many misconceptions about Lyme disease. Indeed, there is much we do not know about the disease, which was only recognized in the US as a distinct entity slightly more than 15 years ago, and the cause of which was first identified only about 10 years ago.
Epidemiology
ECOLOGY AND TRANSMISSION
Borrelia burgdorferi is transmitted by ticks of the Ixodid species. In the US, the common vectors are Ixodes dammini (the deer tick), reported to be the same species as I scapularis, in the Northeast and the Midwest and I pacificus (the western black-legged tick) on the Pacific Coast. Ixodes ticks are much smaller than the common wood tick; the nymphal Ixodes tick is about the size of a pencil point (1 to 2 mm).
