What is soft tick relapsing fever (STRF)?

Soft tick relapsing fever (previously called tick-borne relapsing fever or TBRF) is a disease caused by bacteria called Borrelia hermsii that are carried by soft ticks. STRF is uncommon in California – about 1–10 cases of STRF are reported in California each year.

How do people get STRF?

People get STRF when they are bitten by an infected soft tick. Most people are bitten and infected while staying overnight in rural mountain cabins or camping in similar areas during the summer months.

Soft ticks typically feed on rode​nts, such as squirrels, chipmunks, and mice, in their nests. Soft ticks may also bite and feed on other animals and humans.

The bite of a soft tick is painless. They attach to the skin and feed for only a few minutes, then return to the rodent nest or to a dark, protected location in the building. Soft ticks often feed at night, so many people are bitten while sleeping and never see the tick or realize they were bitten.​

What are the symptoms of STRF?

People who have STRF develop a sudden high fever (104–105°F), chills, headache, and muscle aches up to 3 weeks after being bitten by an infected tick. They may also have nausea, vomiting, abdominal pain, and a rash. These symptoms last 3–5 days and then quickly disappear.

A few days later, the fever and other symptoms come back (relapse). This cycle may continue for several weeks if not treated.

If you develop these symptoms, you should see a doctor or healthcare provider right away and tell them if you've recently stayed in a cabin at high elevation or were camping in similar areas.

STRF can be serious for a person who is pregnant. STRF during pregnancy can cause pregnancy loss or premature birth.​

How is STRF diagnosed and treated?

STRF is often diagnosed during the time when a person has a high fever. During this time, a healthcare provider can take a blood sample and look at the blood under a microscope to see if STRF bacteria are there. STRF can also be diagnosed by other blood tests that are performed in laboratories.

STRF can be treated with antibiotics prescribed by a healthcare provider. Most people with STRF start to feel better within 1–3 days after starting antibiotics. In some cases, a person's symptoms may get worse in the first 24 hours after starting antibiotics. A healthcare provider may suggest pain relievers until the symptoms improve. Although STRF can be severe for some, people rarely develop long-term health problems or die from STRF.

Whe​re are soft ticks found in California?

​Soft ticks are mainl​​y found in forested foothill and mountain elevations above 3,000 feet, such as in the Sierra Nevada Mountains or Tahoe Basin region. Soft ticks live in dark, cool places such as rodent nests, shaded wood piles outside buildings, and between walls, under carpets, or beneath floorboards inside buildings. 

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​Soft ticks are different from other ticks that spread diseases like Lyme disease (called hard ticks). Unlike hard ticks, soft ticks are rarely found outdoors in natural vegetation because they live in rodent nests. 

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How do I ​protect myself from STRF?

The best way to prot​ect yourself from STRF is to keep soft ticks out of and away from your home or place where you are staying. Since soft ticks usually feed on rodents and live in their nests, it's important to keep rodents out of and away from your home or living space as well.  

If you own or manage a cabin, lodge, hotel or other living space at high elevation in California:

• Inspect the inside and outside of the building for evidence of rodents.

• Look for holes or gnaw marks in the walls, droppings, and/or nests. If you find evidence of rodents:

• Place snap traps to catch rodents (do not use glue traps or live traps).

• Safely clean up and remove dead rodents, droppings, and roden​​t nests. 
  

• Seal cracks and openings (the width of a pencil or larger) where rodents can get in, including gaps around pipes and under doorways. 

• Remove items that rodents could use for nesting materials or a place to make a nest:
  

• Newspapers
  

• Cardboard boxes
  

• Wood piles close to the house

If you have questions about rodent control or how to safely clean up after rodents, contact your loca​l vector control agency or a licensed pest control operator.

If you are staying in a mountain cabin, condo, or any other kind of lodging at high elevation in California:

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  Be aware of the place(s) you will be sleeping and take steps to protect yourself:

• Sleep up off the ground on a bed or a cot – do not sleep on the floor. Make sure sheets and blankets do not touch the ground. 
  

• Whenever possible, pull the bed away from the wall so it doesn't touch the wall. This keeps ticks from having easy access to you and your bed. 
  

• 
  If staying in a cabin that hasn't been used for a while, change and wash all bedding before use.

• If using a sleeping bag that has been in storage and hasn't been used for a while, shake it out and wash before using.
  

• ​Store all food in well-sealed containers.
  

• If you notice signs of rodent activity (droppings, rodent nests, etc.), tell the landlord or building manager.  ​