Pacific Coast tick

Dermacentor occidentalis

Distribution

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

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.

Vector Status

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 has also has been associated with transmission of the agents of tularemia (Francisella tularensis) in human, cats and dogs; RMSF, and Colorado tick fever virus (a Coltivirus) to humans. It may also transmit Anaplasmosis to cattle. These ticks have been implicated in cases of tick-bite paralysis. It is a common human biter.

Resources

The Eco-epidemiology of Pacific Coast Tick Fever in California

Rickettsia 364D: A Newly Recognized Cause of Eschar-Associated Illness in California