American Dog Tick

Dermacentor variabilis

Photo by CDC: Adult Female American Dog Tick

This hard tick has a western distribution on the Pacific Coast and an extensive eastern distribution that extends from Canada to the Gulf of Mexico, west into Kansas, Nebraska and Colorado. Recent records have been collected from both humans and dogs with no recent travel history in Alaska, raising concern about establishment of this tick in this previously non indigenous area. The highest risk of being bitten occurs during the spring and summer months. This species is a vector of the agents of Rocky Mountain spotted fever, human granulocytic anaplasmosis (HGA), human monocytic ehrlichiosis (HME), and Tularemia. It has also been responsible for causing tick paralysis in some hosts. Hosts of this species are medium-sized and large mammals for adults, while immature stages usually feed on rodents. Adult females are most likely to bite humans. It 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 2019: 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 American Dog Tick are not known to occur in Alaska or Hawaii, however recent records of this tick have been documented in Alaska from humans and dogs with no recent travel history.