Here, however, we investigate the ecology of the organisms involved in the spreading of the disease and provide a fascinating look at the process of evolution and the relationship between parasites and their hosts. These terms help describe the co-evolved relationships among the various organisms involved. The agent is the beast that actually makes you sick, and, in the case of Lyme disease, the beast is a spiral-shaped bacterium called Borrelia burgdorferi. It is this bacterium that enters the bloodstream and causes the various symptoms associated with the disease. The vector for Lyme disease is a small spider-like organism called a deer tick.
Humans catch the disease from a bite they get from the tick in which the bacterium lives.
For the deer ticks to complete their life cycle, they must find hosts that they can live on. The life cycle of the deer tick is two years. In New England, where our research on Lyme disease is focused, eggs are laid in the spring, and the larvae hatch about six weeks later in early summer. In the larval stage, the ticks are tiny and have only six legs. The larvae molt the following spring into a nymphal stage that has eight legs.