Lyme disease was first discovered in Lyme, Connecticut after a large number of children were reported with rheumatoid arthritis. Symptoms started around the beginning of summer, which is when the blacklegged tick (Ixodes scapularis) nymphs are most abundant. In 1977, Dr. Steere suggested that the blacklegged tick was likely the vector for Lyme disease. This information caused researchers to begin investigating the blacklegged tick. The disease was first characterized by erythema migrans, also known as a bull’s eye rash, which was found around the site of a tick bite, though it is not found in all cases.
The exact cause of Lyme disease was not discovered until 1981 by researchers at the Rocky Mountain Laboratories where the connection between the blacklegged tick and the causative agent was confirmed. Dr. Willy Burgdorfer noticed larval-type movement within dissected tick cells, which were developing into parasites that were found in deer. While investigating the movement, Dr. Burgdorfer noticed spirochetes in the ticks. They confirmed the association by analyzing reaction of the antibodies from serum of recovering Lyme patients to the spirochete, which two researchers later named Borrelia burgdorferi, after it was confirmed to be the causative agent of Lyme disease. B. burgdorferi is a spirochete bacteria, which provides it with an outer membrane that lacks lipopolysaccharide, an inner membrane, and a thin layer of peptidoglycan layer in between. The spirochete ranges from 5 – 20 micrometers in length and 0.3 micrometers in width. It is a slow growing bacteria that takes between 24 and 48 hours to replicate. The blacklegged tick can also transmit agents such as Anaplasma phagocytophilium and Babesia microti, which cause anaplasmosis and babesiosis respectively. However, the prevalence of these agents is much lower than the prevalence of B. burgdorferi.
More information on the discovery of Lyme disease can be found here: https://www.niaid.nih.gov/topics/lymeDisease/Pages/cause.aspx
Lyme disease has become more widespread throughout the Northeastern United States, each year pushing further and further. Another population of blacklegged tick has also been spreading the B. burgdorferi throughout the Great Lake states, such as Minnesota, Wisconsin, and Michigan. The blacklegged tick is restricted to forested areas, as they require a high relative humidity and optimal temperatures to thrive. These factors may help to slow the migration of the tick through Ohio and other large agricultural states. Years ago, Lyme was not very prevalent in western Pennsylvania and in some counties there were no infected ticks recorded at all. However, every county in Pennsylvania now has at least one infected tick, and in recent years the western counties have been reporting rates higher than counties in the east. Pennsylvania currently has the most reported cases for five years in a row.
More information on Lyme Disease: http://www.cdc.gov/lyme/