Infectious Diseases Lyme Disease

Lyme Disease: From Ticks to Aches

Discovery

Since its first description in 1977, Lyme disease has captured the attention of both the medical community and the public. The investigation that determined the cause and ultimately the treatment of Lyme disease is a classic case of medical research.

In Old Lyme, Connecticut, during the fall of 1975, two concerned mothers began a search for a cause of an unusual number of cases of what appeared to be juvenile rheumatoid arthritis (JRA). Drs. Allen Steere and  Stephen Malawista at Yale University joined the quest, and their initial survey found a cluster of 51 cases of apparent JRA in three communities along the Connecticut River. They also noted some interesting connections among the cases; the disease seemed to limited to one side of the river, and was more common in the warmer months of the year. But the most striking clue was the peculiar “bull’s eye” rash that many of the patients had. A few years later the final piece of the Lyme disease puzzle came when the bacterium Borrelia burgdorferi was located in a deer tick. Researchers now know that Lyme disease is transmitted to people by deer ticks infected with B. burgdorferi. More importantly, they understand how to treat and prevent the disease.

Although originally seen in New England, cases have been reported in all 50 states and in most countries around the world. More than 20,000 cases have been reported to the Centers for Disease Control and Prevention (CDC), with the bulk of them being found in either the northeast/greater Atlantic region, or in the Great Lakes region.

How the Disease is Spread
Understanding and treating Lyme disease requires some knowledge about the life cycle of the deer tick, Ixodes dammini. The tick hatches from eggs in the early spring and sets out looking for food. At this point, it is not yet infected and lives off of the blood of the white-footed mouse, which is often infected with Borrelia burgdoreri. The mouse and tick are not affected by the harmful bacterium, but the tick does become a carrier and can transmit it to animals and people.

After "molting" over the winter, the tick reappears the following spring as a nymph. This is bad news for people and pets because the nymph requires a lot of food and consequently infects many more “hosts,” like dogs, horses and humans. In the fall, the tick will molt into an adult to feed and reproduce. Ixodes dammini’s common name is the deer tick because it prefers to mate on deer Most Lyme disease cases occur in the late spring through fall, when the tick is actively feeding.

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