2. Relapsing Fever (Borrelia)
• Uncommon arthropod-borne infection, characterized by recurrent
episodes of fever.
• Caused by spirochetes of the genus Borrelia,
• A fastidious, microorganism with worldwide distribution that is transmitted to
humans by lice or ticks.
3. 1. Epidemic relapsing fever, or Louse-borne Fever
• Caused by B. recurrentis
• Transmitted from person to person by pediculus humanus, the human body
louse
• Human infection occurs as a result of crushing lice during scratching
2. Endemic Relapsing Fever, or Tick-borne Fever
• Caused by several species of Borrelia
• Transmitted to humans by ornithodoros ticks
4. Epidemiology
• Louse-borne epidemic relapsing fever
• Occur in epidemics, often in association with typhus.
• Epidemics are associated with war, poverty, famine, and poor personal
hygiene.
• Occurs more commonly during the winter.
• The major endemic focus of the disease is the highlands of Ethiopia.
5. • Ornithodoros ticks, which transmit endemic relapsing fever
• Distributed worldwide
• Prefer warm, humid environments and high altitudes
• Found in rodent burrows, caves, and other nesting sites
• Rodents are the principal reservoirs
• Infected ticks gain access to human dwellings on the rodent host
6. Pathogenesis
• The cyclic nature of relapsing fever is explained by ability of Borrelia
organisms to continually undergo antigenic (phase) variation.
• Multiple variants evolve simultaneously during the first relapse, with
one type becoming predominant.
• Spirochetes isolated during the primary febrile episode differ antigenically
from those recovered during a subsequent relapse.
7. • During febrile episodes,
• Spirochetes enter the bloodstream
• Induce the development of specific IgM and IgG antibody
• Undergo agglutination, immobilization, lysis, and phagocytosis
• During remission,
• Borrelia spirochetes may remain in the bloodstream, but spirochetemia is
insufficient to produce symptoms.
• The number of relapses in untreated patients depends on the number
of antigenic variants of the infecting strain.
8. Clinical Manifestations
• Characterized by periods of fever lasting 2–9 days, separated by
afebrile periods of 2–7 days.
• Louse-borne disease has
• A longer incubation period
• Longer periods of pyrexia
• Fewer relapses
• Longer remission periods
• The incubation period of tick-borne disease is usually 8 days, with a
range of 5–15 days.
10. • Signs
• Rash (diffuse, erythematous, macular, or petechial) over the trunk and
shoulders
• During the end of the primary febrile episode, lasts for 1–2 days' duration
• More common in louse-borne fever (25%)
• Lymphadenopathy
• Pneumonia
• Splenomegaly
• Tender hepatomegaly
• Jaundice
11. • CNS manifestations
• Lethargy, stupor, meningismus, convulsions, peripheral neuritis, focal
neurologic deficits, and cranial nerve paralysis
• Principal feature of late relapses in tick-borne disease
• Severe manifestations include
• Myocarditis
• Hepatic failure
• Disseminated intravascular coagulopathy
12. • The initial symptomatic period characteristically ends with a crisis in
2–9 days
• Abrupt diaphoresis, hypothermia, hypotension, bradycardia, profound muscle
weakness, and prostration
• In untreated patients
• The first relapse occurs within 1 wk, followed by usually 3 but up to 10
relapses
• Symptoms during each relapse become milder and shorter as the afebrile
remission period lengthens
13. Diagnosis
• Demonstration of spirochetes in thin or thick blood smears stained
with Giemsa or Wright's stain.
• Loosely coiled spirochetes in the blood during the febrile stage of the disease
• Serologic tests (enzyme immunoassay, Western blotting) are not
standardized.
14. Treatment
• Tetracycline Oral (500mg PO q 6hr) or parenteral for 10 days is the
drug of choice for louse-borne and tick-borne relapsing fever.
• Single-dose treatment with tetracycline (500mg PO) or erythromycin
is efficacious in adults.
• Penicillin and chloramphenicol are also effective.
15. • Jarisch-Herxheimer reactions (JHR)
• Occur within two hours of antibiotic treatment (LBRF – 80%, TBRF – 54%)
• Manifestations include rigors, fever, and hypotension
• Attempts to control this reaction by prior treatment with corticosteroids or
antipyretics have limited success
• Observation for several hours after treatment is recommended
16. Prognosis
• With adequate therapy, the mortality rate for relapsing fever is <5%.
• A majority of patients recover from their illness with or without
treatment after the appearance of anti-Borrelia antibodies.
17. Prevention
• No vaccine is available.
• Avoidance or elimination of the arthropod vectors.
• Louse-borne disease
• Good personal hygiene
• Delousing of persons, dwellings, and clothing with insecticides
• Tick-borne disease
• Rodent-free dwellings
Editor's Notes
After ingestion of an infective blood meal by the louse, the spirochetes penetrate its midgut, migrate to and multiply within the hemolymph And remain viable throughout its lifespan (several weeks)
Tetracyclines, Erythromycin, and Penicillin have proven effective treatments.
