Cranial nerve palsies, as well as motor and sensory radiculitis, may also be seen. Both cardiac and neurologic abnormalities tend to be self-limited, although repeated episodes may occur. Lyme disease is thought to be caused by an infectious agent transmitted by Ixodes ticks, although other vectors could be involved. In California and Oregon, I. pacificus ticks have been implicated. As further evidence for an infectious etiology, antimicrobial therapy has been shown to significantly alter the course of the disease.
Work is underway to identify an agent of the disease and to develop a diagnostic laboratory test.
At present, however, the diagnosis of Lyme disease rests on clinical grounds, based principally on recognition of typical ECM skin lesions in association with cardiac, neurologic, and arthritic abnormalities. The majority of Lyme disease patients become ill in the summer months. Because the full geographical distribution and the number of cases are not known, State and Territorial Epidemiologists and CDC are attempting to identify all cases of Lyme disease that occur in the United States this year. Health care providers are encouraged to report cases to appropriate local and state health departments. Erythema chronicum migrans and Lyme arthritis.