Pacific Coast Tick

Dermacentor occidentalis

This hard tick is well distributed throughout California and along the Pacific coastal areas of US, found predominantly in shrublands, chaparral, and along trails from Oregon to northern Baja California and Mexico. Hosts for this tick include a wide range of mammals and birds. Immature stages commonly feed on rodents, especially squirrels; adults feed on cattle, horses, and deer. It transmits Rickettsia species 364D (proposed name Pacific Coast Tick Fever), a form of spotted fever; where nymphal and larval stages of D. occidentalis have been implicated as the primary vectors of R. philipii to humans. It may also transmit Tularemia to humans, cats, and dogs, and Anaplasmosis to cattle. These ticks have been implicated in cases of tick-bite paralysis. 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.