Which tick is a main vector of Rocky Mountain spotted fever in the eastern United States?

The American dog tick is a main vector of Rocky Mountain spotted fever in the eastern United States.

The American dog tick is Dermacentor variabilis, a hard tick native to much of North America. In the eastern United States, it is an important vector of Rickettsia rickettsii, the bacterium that causes Rocky Mountain spotted fever. The tick can acquire the bacterium while feeding on an infected host and later transmit it during another blood meal.

Despite its common name, the American dog tick feeds on many animals. Adults frequently parasitize dogs and other medium-sized or large mammals, while immature stages typically feed on small mammals. It can also bite humans. The species is recognized by ornate pale markings on its scutum, although identification can be difficult without close examination.

The geographic wording matters. Rocky Mountain spotted fever is not transmitted by one tick species everywhere: Dermacentor andersoni is important in parts of the western United States, while D. variabilis is especially significant in the East. “Deer tick” usually means Ixodes scapularis, the principal Lyme-disease vector, and “lone star tick” means Amblyomma americanum.