Borrelia recurrentis

• Causes Louse-borne relapsing fever (LBRF)

Background

Microbiology

• Spirochete"Spirochete" is not in the list (coccus, bacillus, coccobacillus, diplococcus, spirochete, curved, pleomorphic, yeast, mold) of allowed values for the "Shape" property.
• Serotypes are determined by the outer membrane variable major proteins (vmp)
• Grow in modified Kelly medium and stained by Wright stain (in peripheral blood film)

Epidemiology

• Vector-borne disease transmitted by the human body louse (Pediculus humanus humanus)
• LBRF was present nearly worldwide prior to World War II, but is now present in Ethiopia
• Associated with homelessness and refugee camps

Pathophysiology

• During febrile periods, spirochetes divide rapidly and cause a spirochetemia
• This is followed by an immune response to the vmp proteins, which clears the spirochetemia and the patient becomes afebrile
• The vmp proteins undergo rearrangement, evading the immune system and allowing another spirochetemia
  • This is the cause of the relapsing fever

Clinical Manifestations

• Incubation period of 7 days (range 2 to 18 days)
• Relapsing fevers: febrile for 3 days, afebrile for 7 days
• Some patients will have lymphadenopathy, hepatosplenomegaly, and a rash
• Rare complications include lymphocytic meningitis, Bell palsy and other cranial nerve palsies, paralysis, seizure, uveitis, endophthalmitis, ARDS, and myocarditis
• Can cause spontaneous abortion in pregnant women
• May be septic, with multiple organ involvement
• May have a Jarisch-Herxheimer reaction following empiric antibiotics

Differential Diagnosis

• Typhus
• Malaria
• Typhoid fever
• Leptospirosis
• Viral hepatitis
• Dengue

Diagnosis

• Often seen on blood film
  • Giemsa or Wright stains
  • 70% sensitive during febrile period for TBRF, lower for LBRF
• Acute-convalescent serology with IFA/EIA
  • May cross-react with Lyme disease
• Can cause a false-positive VDRL
• Can be cultured with modified Kelly medium

Management

• First-line: Doxycycline 200 mg po once
• Alternatives:
  • Penicillin G 400-800 kU IM once
  • Erythromycin 500 mg po once

Prevention

• Can do post-exposure prophylaxis with doxycycline 200 mg po once followed by 100 mg daily for 4 days