Ornithodoros coriaceus

The soft tick (Argasidae) identified below pose health risks for humans and animals in the Pacific Southwest. Soft ticks are recognized by their mouth parts being on the underside of the body. Unlike hard ticks, soft ticks do not have a hard outer shell (scutum).

Pajahuello Tick Habitat

Pajahuello ticks live in the soil and leaf litter below chaparral and oak trees. This tick species have been found in foothill areas of California, northern and central Nevada, and southeastern Oregon, as well as in Mexico, at elevations of 600 to 8,000 feet.

Pathogens & Diseases

Pajahuello ticks can cause necrotic ulcers and swelling in humans, subsequent to a tick bite. Repeated tick bites can often worsen the symptoms caused by previous bites.

Pajahuello ticks can also carry and transmit deltaproteobacterium (pathogen) that causes Foothill abortion, also known as Epizootic Bovine Abortion (EBA), when the tick feeds on a pregnant cow or heifer. The bite of the Pajahuello tick on nonimmune pregnant heifers or cows 100 to 145 days before giving birth can result in abortion or the birth of weak calves.

Resources & References

Herms, W. (1916). The Pajaroello Tick (Ornithodorus coriaceus Koch) with Special Reference to Life History and Biting Habits. The Journal of Parasitology, 2(3), 137-142. doi:10.2307/3271197

University of California, Agriculture and Natural Resources (UCANR):


Learn about the tick species that pose health risks for both humans and animals in the region and view public health information on ticks.


The Border Tick and Rickettsia Surveillance (BiTeRS) program of PacVec offers services to enhance surveillance for ticks and tick-borne pathogens of human health concern in California and Arizona.

The Pacific Southwest Regional Center of Excellence in Vector-Borne Diseases is supported through Cooperative Agreement Number 1U01CK000649 between the Centers for Disease Control and Prevention (CDC) and the University of California, Davis.

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