Figuring Out the Where and Why of the Disease
Understanding and preventing any infectious illness--not just Lyme disease--requires an understanding of its ecology: the interactions between the disease agent or pathogen, any vectors, its host(s) or reservoir(s), and human behavior. The Lyme disease pathogen is the spirochete; the vector is Ixodes scapularis, commonly known as the “deer tick,” primarily in its larval and nymphal stages; the major reservoir is the white-footed mouse (which is also the preferred intermediate host for the nymphal and larval ticks); the preferred host for the adult tick is the deer; and the relevant behaviors are deforestation, reforestation, and suburban development of deer/tick habitat. Other smaller mammals, some birds, and humans, can also serve as hosts for the tick.

More Woods + More Deer
The North American white-tailed deer population has been exploding since the mid-1900’s because of human-induced environmental changes. Forest has returned to much of the land cleared in the last century for farming, and suburban neighborhoods have developed. There’s more forest in many places than any time in the previous hundred years. This secondary forest occurs patchily around homes, creating “edge habitat,” which is ideal for deer, but not for the predators that used to control their numbers. The deer’s only remaining significant predator is man, and hunting is restricted in suburban areas.