Tick-Borne Relapsing Fever
Repeated bouts of fever from a soft tick bite
Quick Facts
- Type: Tick-borne bacterial infection
- Spread by: Soft ticks, often in rustic cabins
- Hallmark: Recurring episodes of high fever
- Treatment: Antibiotics
Overview
Tick-borne relapsing fever (TBRF) is an infection caused by Borrelia bacteria that are spread to people through the bites of certain soft ticks. Unlike the hard ticks that cause Lyme disease, these soft ticks feed quickly, often at night, and then leave, so people frequently never notice the bite. The ticks tend to live in rodent nests in the walls and floors of rustic cabins, particularly in mountainous areas, and outbreaks have been linked to staying overnight in such cabins.
The defining feature of the illness is repeated episodes of high fever. After an initial bout of several days of fever, the symptoms ease, only to return after about a week, and this pattern can repeat several times if the infection is not treated. While TBRF can make a person quite ill, it usually responds well to antibiotics. Prompt recognition is important, especially because treatment can occasionally trigger a strong short-term reaction that needs monitoring.
Symptoms
Symptoms usually begin about a week after a tick bite and come in recurring cycles.
- Sudden high fever, often with shaking chills
- Headache, muscle and joint aches
- Nausea, vomiting, and loss of appetite
- Fatigue and weakness
- Sometimes a rash, dizziness, or sensitivity to light
A typical fever episode lasts about three days, followed by roughly a week without fever, and then another episode. Each cycle may become milder. Without treatment the relapses can continue, and complications can develop. Pregnant women may become more severely ill.
Causes
Tick-borne relapsing fever is caused by Borrelia bacteria transmitted by soft ticks.
- Soft tick bites: The ticks usually bite at night, feed for only a short time, and leave, so the bite often goes unnoticed.
- Rodent reservoirs: The ticks live in rodent burrows and nests, including those in the walls of rustic or seldom-used cabins.
- Exposure settings: Sleeping in rodent-infested cabins, particularly in mountainous regions, is a classic source of infection.
The relapses occur because the bacteria periodically change their surface so they can temporarily evade the immune system, leading to repeated waves of illness.
Risk Factors
- Sleeping or staying in rustic, rodent-infested cabins
- Camping, hiking, or vacationing in affected mountainous areas
- Exposure to rodent nests in buildings
- Outdoor occupations in regions where the soft ticks live
- Travel to areas where relapsing fever occurs
Diagnosis
Diagnosis relies on recognizing the pattern of relapsing fever along with a history of possible exposure.
- History: Asking about recent stays in rustic cabins and the recurring fever pattern is key.
- Blood smear: During a fever episode, the bacteria can sometimes be seen directly in a blood sample under the microscope, which is a distinctive finding.
- Additional tests: Blood antibody or molecular tests can support the diagnosis.
Because the bacteria are most visible in the blood during a fever spike, the timing of testing matters.
Treatment
Tick-borne relapsing fever is treated with antibiotics, which usually clear the infection effectively.
- Antibiotics: Medicines such as doxycycline are commonly used, with alternatives like penicillin or erythromycin for certain people, including children and pregnant women.
- Monitoring for a reaction: Treatment can trigger a short, intense reaction (the Jarisch-Herxheimer reaction) with worsening fever, chills, and a drop in blood pressure within hours; this is monitored, sometimes in the hospital, and managed supportively.
- Supportive care: Rest, fluids, and fever control aid recovery.
Most people recover fully with antibiotics, and the relapses stop once the bacteria are cleared.
Prevention
- Avoid sleeping in rodent-infested cabins and rooms
- Rodent-proof cabins by sealing gaps and removing nests with care
- Use insect repellent and protective clothing in tick areas
- Air out and inspect seldom-used cabins before staying overnight
- Treat sleeping areas in high-risk cabins as advised
When to See a Doctor
See a doctor if you develop recurring episodes of high fever, especially after staying in a rustic or rodent-infested cabin, even if you do not recall a tick bite. Mention the cabin stay, as it is an important clue. Seek emergency care for very high fever, confusion, fainting, severe weakness, trouble breathing, or signs of a sudden severe reaction such as a rapid drop in blood pressure, and pregnant women with these symptoms should be evaluated urgently.
Frequently Asked Questions
Why is it called relapsing fever?
The illness causes repeated episodes of high fever separated by fever-free periods. A bout of fever lasts about three days, then symptoms ease for roughly a week before another episode begins. This happens because the bacteria periodically change their surface to evade the immune system.
How do people get tick-borne relapsing fever?
It spreads through the bite of certain soft ticks that live in rodent nests, often in the walls of rustic cabins. These ticks usually bite at night and feed briefly, so people rarely notice the bite. Staying overnight in rodent-infested cabins is a common source.
How is it treated?
Antibiotics such as doxycycline are used, with alternatives like penicillin or erythromycin for children and pregnant women. Treatment usually clears the infection and stops the relapses. Doctors watch for a short, intense reaction that can occur soon after the first dose.
What is the Jarisch-Herxheimer reaction?
It is a short but intense reaction that can occur within hours of starting antibiotics, with worsening fever, chills, and a temporary drop in blood pressure. It happens as many bacteria are killed at once. It is monitored and treated supportively, sometimes in the hospital.
How can I prevent it?
Avoid sleeping in rodent-infested cabins, rodent-proof and clean cabins before staying overnight, and use insect repellent and protective clothing in tick areas. Inspecting and airing out seldom-used cabins before use reduces the risk of soft tick bites.
References
- Centers for Disease Control and Prevention (CDC). Tickborne Relapsing Fever (TBRF).
- MedlinePlus, U.S. National Library of Medicine. Relapsing fever.
- Mayo Clinic. Relapsing fever.
- National Institute of Allergy and Infectious Diseases (NIAID).