Lyme disease is transmitted through the bite of an infected tick. The Ixodes tick, also known as the blacklegged tick or deer tick, is the species that commonly carries and transmits the Lyme disease bacterium. In the eastern and midwestern states of the U.S. during the spring, summer, and fall, the main type of tick that carries the bacterium is Ixodes scapularis or deer tick. In the western U.S., Ixodes pacificus—the western blacklegged tick—primarily carries Lyme disease bacteria.
It's important to note that not all ticks carry Lyme disease. Immature ticks, called nymphs, are about the size of a poppyseed and adults are about the size of a sesame seed. Ticks at both of those life stages can transmit the bacteria that causes the disease.
