Borrelia recurrentis

Background

Spirochete
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)

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

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

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

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

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