Relapsing Fever Ticks


Ornithodoros spp.


Ornithodoros ticks get their common name because of their ability to transmit tick borne relapsing fevers (TBRF). The appearance of Ornithodoros adult ticks looks much like many other species of soft ticks – eight legs, rounded body, dimples on their body, and mouthparts hidden from view when seen from above, unlike hard ticks, whose mouthparts are easily seen protruding from their head. Relapsing fever ticks seldom come into contact with people, as the pests typically prefer to feed on hosts in their nests or burrows


The relapsing fever tick’s diet consists of blood they get from their hosts. Their preferred habitats are dark, cool places where their hosts nest. Examples of such habitats include outside woodpiles, house crawl spaces, between walls, or beneath floorboards inside rustic cabins or in caves. More specifically, Ornithodoros hermsi, the tick responsible for most cases of TBRF in the United States, prefers coniferous forests at altitudes of 1,500 to 8,000 feet, where it feeds on tree squirrels and chipmunks. The other species found in the U.S. are O. parkeri and O. turicata. Both inhabit low-altitude caves and the burrows of southwestern ground squirrels, prairie dogs and burrowing owls.

When suitable hosts are scarce, these ticks may take a blood meal from humans or pets. or in other areas near where the ticks are found. Most bites experienced by humans happen during the night. People are usually unaware of the bites, which remain largely painless.


Relapsing fever tick eggs are laid in batches by female ticks, with each batch of eggs produced after taking a blood meal. During her lifetime, a female may lay from 25 to several hundred eggs. Like most other ticks, relapsing fever ticks go through four developmental stages – eggs, larvae, nymphs and adults.


Unlike hard ticks, soft ticks do not embed themselves into the skin of their host. Instead, they feed for only about 15-30 minutes and then leave the host. Therefore, the presence of an embedded tick on the body is not a sign of a relapsing fever tick. However, the occurrence of the symptoms of tick-borne relapsing fever will indicate the presence of these ticks in a host’s nest or burrow.


The regions where relapsing fever has been reported generally best identify the distribution of Ornithodoros ticks. This area includes 15 states: Arizona, California, Colorado, Idaho, Kansas, Montana, Nevada, New Mexico, Ohio, Oklahoma, Oregon, Texas, Utah, Washington, and Wyoming.


TBRF is a bacterial infection with symptoms that include repeated episodes of fever, headache, muscle, and joint aches, and nausea.  If you suspect the presence of relapsing fever ticks, the best thing to do is contact your pest management professional (PMP) for their assistance. They will provide correct identification of the tick and prepare a tick management plan. The plan may include:

  • Inspect your home or other dwelling for signs of rodent activity
  • Eliminate all rodent nesting material.
  • Provide rodent exclusion to seal all holes in the foundation and walls, plus make sure screens are in good repair.
  • When ticks are already inside, contact your PMP for insecticide application, if needed.
  • Wear protective clothing in areas where ticks may be present.
  • Use both skin and clothing repellents that are registered with the Environmental Protection Agency (EPA) and recommended by your family physician.