Lyme Disease and the Environment

Lyme disease is mainly found in the eastern United States and upper Midwest. Lyme disease is caused by the bacterium Borrelia burgdorferi. The bacteria is passed onto humans by the bite of an infected tick, primarily Ixodes scapularis (also known as the black legged or deer tick). 

The Lyme disease bacterium is carried mostly by deer ticks. Ticks are most likely to spread the Lyme disease bacterium during their pre-adult stage (nymph). Nymphs are brown, very small and difficult to see. Nymphs are most common between May and July and found in tall grasses and brush of wooded areas. Towards the end of summer and into fall, ticks mature and are less likely to spread disease.

Ticks painlessly attach themselves to a host (individual person or animal) and feed on the host's blood until they're swollen to many times their normal size. Scientific data suggests that ticks need to remain attached for 24–48 hours before the host is infected with the bacterium. An attached tick that looks swollen could have been attached long enough to transmit bacteria.