Photo by CDC: Rocky Mountain Wood Tick

Dermacentor andersoni

This hard tick is one of the most common ticks encountered by humans and pets in Colorado. This species is the primary vector for the Colorado Tick Fever Virus. They may also transmit the agents of Rocky Mountain spotted fever, Tularemia, and Q-fever. It is commonly responsible for tick paralysis in humans, livestock, and wild mammals (along with several other tick species worldwide) and is known to occur throughout the Rocky Mountain States and southwestern Canada from elevations of 4,000 to 10,500 feet.  Hosts of this species include medium-sized and large mammals for adult ticks; whereas immature stages usually feed on rodents. This species is a common human biter.

Visit University of Rhode Island’s TickEncounter Resource Center for additional photos to help in the identification of ticks.

CDC Distribution Map: This map provides general insight into the expected distribution of these human-biting ticks in the contiguous United States. Populations of ticks may be found outside noted areas. Naturally occurring populations of the Rocky Mountain Wood Tick are not known to occur in Alaska or Hawaii.