LYME DISEASE

    General Information

    Ticks are vectors of several disease-causing agents in the United States. They are known to transmit several organisms directly to humans, notably Rocky Mountain spotted fever (R.M.S.F.) rickettsiae, babesiosis piroplasms, and Lyme disease spirochetes in the Northeast. Although all of these diseases remain a constant threat, Lyme disease increased to near epidemic proportions in the 1980's. Today, Lyme disease has become the most prevalent arthropod-borne disease in North America and has emerged as one of the most significant threats to the public's health. Nationally, reported cases of the disease increased nine fold between 1982 and 1988.

    Lyme disease is a chronic debilitating disease that may cause muscoskeletal, cardiac and central nervous system disorders, often preceded by a circular rash or skin lesion (erythema migrans or EM). In the northeastern United States, the incidence of Lyme disease has increased largely due to an increase in both the distribution of the numbers of vector ticks, Ixodes scapularis, and the etiological agent, Borrelia burgdorferi. Consequently, the public's interest in the disease has also gained momentum.

    The blacklegged tick, I. scapularis, is considered to be the most important vector of the Lyme disease spirochete, B. burgdorferi, in the Northeast and the upper Midwest and may infest a variety of hosts. Larvae and nymphs are known to infest 31 mammalian species and 49 avian species, and the adults have been found on at least 13 species of medium- or large-sized mammals. Peromyscus leucopus is by far the most significant reservoir host for B. burgdorferi. However, where these mice are not prevalent, other hosts, such as chipmunks (Tamias striatus) and meadow voles (Microtus pennsylvanicus), may serve as minor reservoir hosts of B. burgdorferi. Some small mammals, such as short-tailed shrews (Blarina brevicauda); masked shrews (Sorex cinereus); and meadow jumping mice (Zapus hudsonicus) have been found to have little or no reservoir potential. Still other species, such as the raccoon (Procyon lotor) and the Virginia opossum (Didelphis virginiana) have yet to be fully assessed for their reservoir potential

    Transovarial transmission, or passage through the egg to the next generation, of B. burgdorferi in I. scapularis is relatively rare (<1.0%). Therefore, the primary acquisition of the spirochete occurs during the time the larvae are attached to the host species (usually P. leucopus). Subsequently, the resulting nymphal and adult stages will emerge already infective and will be able to transmit the spirochete to previously uninfected hosts. These hosts may include other mice, larger mammals or even humans.

    LYME DISEASE

    BIOMONICS OF BLACKLEGGED DEER TICKS

    EPIZOOTIOLOGY

    SYMPTOMS, DIAGNOSIS, AND TREATMENT

    TRL Home Page / Ticks / Research / Links / URI


    TRL, © Copyright 2000.