Relapsing Fever: Complete Clinical Guide to Borrelia Infection
Clinical Medicine Year 3 • louse-borne and tick-borne relapsing fever
Why the fever returns
Relapsing fever is an acute infection caused by antigenically variable Borrelia spirochetes. A high-density bloodstream episode produces abrupt fever; antibodies clear one surface-antigen variant, but a new variant emerges and causes another episode. The patient may appear well between attacks, making the history of fever cycles crucial.
Learning outcomes
- Distinguish louse-borne from tick-borne relapsing fever in organism, reservoir and transmission.
- Explain spirochaetaemia, antigenic variation and recurrent febrile episodes.
- Recognise haemorrhage, jaundice, myocarditis, shock, meningitis and pregnancy complications.
- Diagnose during fever using blood film, PCR or reference tests and distinguish malaria/sepsis.
- Start effective therapy, anticipate Jarisch–Herxheimer reaction and control vectors.
1. Organisms and epidemiological forms
| Feature | Louse-borne relapsing fever | Tick-borne relapsing fever |
|---|---|---|
| Main organisms | Borrelia recurrentis | Several species; African examples include B. duttonii and B. crocidurae |
| Vector | Human body louse, Pediculus humanus corporis | Soft ticks, especially Ornithodoros |
| Reservoir | Humans; louse-borne cycle is human-to-human | Rodents and other animals maintain a zoonotic cycle |
| Risk setting | Overcrowding, displacement, homelessness, prisons, poor hygiene | Rural/tick-infested sleeping areas, animal burrows and rodent exposure |
| Public-health priority | Delousing, hygiene, clothing/bedding and outbreak control | Tick avoidance, rodent control, housing and environmental measures |
2. Microbiology and transmission
Borrelia are slender, actively motile spirochetes with loose coils and axial filaments. Louse-borne organisms infect lice; when an infested louse is crushed, organisms in its tissues contaminate abraded skin or mucosa. Tick-borne organisms are transmitted during the brief feeding of an infected soft tick. Unlike Lyme disease, this African relapsing-fever syndrome is often an acute high-spirochaete-burden illness.
Transmission is favoured by poverty, overcrowding, poor access to bathing and laundry facilities, displacement, sleeping in rodent/tick habitats and lack of vector control. Ordinary casual contact without vector or contaminated blood exposure is not the usual route.
3. Pathogenesis and antigenic variation
- Inoculation through skin or mucosa is followed by rapid multiplication.
- High spirochaetaemia produces cytokine release, endothelial injury and the first fever.
- Neutralising antibodies clear the dominant surface-antigen variant, so fever falls.
- A new antigenic variant escapes the antibodies and multiplies, causing another febrile episode.
- Repeated cycles can produce three to five relapses; severe inflammation injures the myocardium, liver, brain and coagulation system.
The rapid fall in organisms after antibiotics releases inflammatory products and can produce a Jarisch–Herxheimer reaction, sometimes more dangerous than the original fever.
4. Clinical presentation
4.1 Incubation and first attack
Incubation is commonly 5–10 days. Fever begins abruptly, often 39–40°C, with rigors, severe headache, myalgia, arthralgia, nausea, vomiting, weakness and photophobia. Dry cough and abdominal discomfort may occur.
4.2 Physical signs
- Tachycardia, hypotension or a transient fall in blood pressure after rigors.
- Hepatomegaly, splenomegaly, jaundice and abdominal tenderness.
- Petechiae, epistaxis, gingival bleeding or subconjunctival haemorrhage.
- Confusion, meningism, cranial-nerve signs or seizures in CNS disease.
- Myocarditis, heart failure, arrhythmia or pulmonary oedema in severe infection.
4.3 The relapse
After 3–7 days of fever, the temperature may fall with dramatic improvement. A symptom-free interval is followed by another abrupt fever when an antigenic variant emerges. Relapses may be milder or more severe and should not be mistaken for malaria treatment failure without testing.
4.4 Pregnancy and children
Severe fever and spirochaetaemia may cause miscarriage, preterm birth, fetal infection or neonatal disease. Children may present with irritability, poor feeding, vomiting, seizures or shock. Use age/pregnancy-compatible treatment and refer severe cases.
5. History and examination
Ask about
- Number, duration and spacing of fever attacks; rigors and recovery between episodes.
- Lice, overcrowding, homelessness, prison/displacement, infested bedding, rodents, ticks, rural sleeping and animal burrows.
- Bleeding, jaundice, headache, photophobia, confusion, weakness, chest pain, dyspnoea and reduced urine.
- Pregnancy, HIV, malaria treatment, antibiotics and contact with similar febrile patients.
Examine
Measure temperature repeatedly, pulse, blood pressure, respiratory rate, oxygen saturation, capillary refill, mental state, hydration and urine output. Look for lice/nits, petechiae, jaundice, hepatosplenomegaly and subconjunctival haemorrhage. Perform cardiac, respiratory and neurological examinations, including meningism and focal deficits.
6. Diagnosis
6.1 Blood during the fever
Demonstration of spirochetes is most likely during a febrile episode, when organism density is high. Thick and thin blood films examined by experienced staff may show long, motile organisms; repeat films can be needed. PCR and reference laboratory methods improve confirmation.
6.2 Supporting tests
- FBC and platelets for anaemia, thrombocytopenia and severe disease.
- Glucose, electrolytes, urea/creatinine, liver tests, bilirubin and coagulation.
- Malaria testing, blood cultures and sepsis work-up according to local epidemiology.
- ECG/troponin/echo for myocarditis; chest imaging for pulmonary oedema; LP and neuroimaging for CNS signs after safety assessment.
6.3 Do not over-rely on serology
Serological tests may support retrospective diagnosis but often cannot distinguish current from previous infection early enough to guide emergency care. A compatible febrile illness with exposure and spirochaetaemia deserves treatment even while confirmatory testing is pending.
7. Differential diagnosis
| Condition | Why it resembles relapsing fever | Useful distinction |
|---|---|---|
| Malaria | Rigors, fever cycles, splenomegaly, anaemia | Repeated malaria tests, parasite morphology and exposure; co-infection possible |
| Enteric fever | Prolonged fever, abdominal symptoms | Blood culture, bowel complications and exposure history |
| Leptospirosis | Fever, myalgia, jaundice, renal injury | Water/animal urine exposure, conjunctival suffusion, renal pattern |
| Rickettsial disease | Fever, headache, vector exposure, rash | Eschar/rash and serology/PCR where available |
| Meningitis/sepsis | Fever, confusion, hypotension | Acute microbiology, CSF and source examination |
| Viral haemorrhagic fever | Fever, bleeding, shock | Outbreak/travel history, isolation/public-health pathway and specific tests |
8. Treatment
Admit patients with severe disease, pregnancy, CNS signs, bleeding, hypotension, organ dysfunction or diagnostic uncertainty. Start a locally recommended effective antibiotic—options used in different protocols include doxycycline, penicillin-class therapy, ceftriaxone or another active agent—after considering pregnancy, age, CNS involvement and regional guidance. Do not delay life-saving therapy for a negative initial film.
Uncomplicated adult disease
Use the national recommended oral or parenteral antibiotic and complete the prescribed course. Review vector exposure and observe for reaction after the first dose.
Severe, CNS or pregnancy disease
Use an appropriate IV/CNS-penetrating or pregnancy-compatible regimen with specialist advice, monitor perfusion and organ function and treat complications in hospital.
Supportive care
Oxygen, cautious IV fluids, antipyretics, glucose/electrolyte correction, blood products for significant bleeding and vasopressors/diuretics for shock or pulmonary oedema as indicated.
9. Jarisch–Herxheimer reaction
Within minutes to hours of the first effective dose, the patient may develop abrupt worsening fever, chills, tachycardia, tachypnoea, hypotension, myalgia, confusion, bleeding, pulmonary oedema or fetal distress. Cytokines including TNF, IL-6 and IL-8 rise rapidly.
- Warn the patient and ensure close observations, IV access and resuscitation equipment before the first dose.
- Give oxygen, cautious isotonic fluid and antipyretic; use vasopressor support for persistent shock.
- Monitor ECG, urine output, respiratory status, coagulation and fetal wellbeing where relevant.
- Distinguish reaction from anaphylaxis: urticaria, angio-oedema and bronchospasm suggest allergy, whereas fever/rigors/hypotension after spirochaete killing suggest Herxheimer.
- Continue the appropriate antibiotic unless a true severe allergy is present; involve specialists if uncertain.
10. Complications
- Myocarditis, arrhythmia, congestive heart failure and pulmonary oedema.
- Jaundice, hepatitis, acute kidney injury and electrolyte disturbance.
- Thrombocytopenia, DIC, epistaxis, gastrointestinal or cerebral bleeding.
- Meningoencephalitis, seizures, delirium, coma, neuropathy or stroke-like deficits.
- Shock, secondary bacterial infection, miscarriage, preterm birth and fetal/neonatal disease.
- Severe Herxheimer reaction with respiratory failure or death.
11. Prevention and outbreak control
Louse-borne disease
- Delouse the patient and close contacts; wash or heat-treat clothing and bedding.
- Improve access to bathing, laundry, clean clothing and uncrowded sleeping areas.
- Use insecticides under public-health guidance and investigate clusters in prisons, shelters and displacement settings.
Tick-borne disease
- Repair housing, plaster cracks, remove rodent nests and control soft ticks.
- Avoid sleeping on infested floors/animal burrows; use protective clothing and insecticide-treated materials where appropriate.
- Educate communities to seek care for abrupt recurrent fever and prevent untreated household exposure to ticks.
12. Clinical reasoning examples
Example A: fever returns after recovery
A patient improves for four days then develops 40°C fever, headache and petechiae. Ask about lice/ticks, repeat a blood film during fever, test for malaria and sepsis and anticipate Herxheimer if treatment is started.
Example B: hypotension after first dose
Chills, fever, tachycardia and low blood pressure two hours after antibiotic administration may be a Jarisch–Herxheimer reaction. Resuscitate and monitor; look for urticaria/angio-oedema to distinguish anaphylaxis.
13. Examination pearls
- The defining pattern is recurrent febrile episodes separated by apparent recovery.
- Blood-film sensitivity is highest during fever.
- Louse-borne disease is human-to-human; tick-borne disease is zoonotic.
- Prepare for Herxheimer reaction before the first dose.
- Bleeding, jaundice, myocarditis and meningitis determine severity.
14. References
- SlideShare: Relapsing Fevers — Borrelia species, vectors, pathogenesis, recurrent symptoms, complications, diagnosis, treatment and prevention.
- WHO and national guidance for relapsing fever and vector-borne spirochaetal disease.
- Uganda Clinical Guidelines and local outbreak protocols.
