Steere and others became aware that Lyme disease was a multisystem illness that involved not only joints and skin, but could also involve the heart and the nervous system. In 1982, Burgdorfer identified spirochetes in the tick midgut region. Soon thereafter this spirochete was isolated from patients, classified as a Borreli a species, and given the name Borrelia burgdorferi . In the United States, Borrelia burgdorferi is known to be transmitted by certain Ixodes ticks. Ixodes scapularis or deer tick is found predominantly in the northeastern United States as well as in Minnesota and Wisconsin.
Ticks can feed on humans at any stage, but most often the nymph transmits the spirochete.
In the western United States, limited information is available on the tick vector, its life cycle, and its preferred hosts. Animal studies have shown that Ixodes ticks must remain attached for at least 24 hours in order to transmit B. burgdorferi . Dermacentor ticks, which are common in eastern Washington, are not competent vectors of Lyme disease. Inc. All rights reserved. Ixodes pacificus nymph on the finger of an 8 year old child.