 |
Relapsing fever is a recurring febrile disease caused by several species of Borrelia and transmitted by lice or ticks. Symptoms are recurrent febrile episodes with headache, myalgia, and vomiting lasting 3 to 5 days, separated by intervals of apparent recovery. Diagnosis is clinical, confirmed by staining of peripheral blood smears. Treatment is with a tetracycline or erythromycin.
The insect vector may be soft ticks of the genus Ornithodoros or the human body louse, depending on geographic location. Louse-borne relapsing fevers are rare in the US and endemic only in the highlands of Central and East Africa and the Andes of South America; the tick-borne fevers are endemic in the Americas, Africa, Asia, and Europe. In the US, the disease is generally confined to the western states, where occurrence is highest between May and September.
The louse is infected by feeding on a febrile patient. If the louse is crushed on a new host, Borrelia are released and can enter abraded skin or bites. Intact lice do not transmit disease. Ticks acquire the spirochetes from rodent reservoirs. Humans are infected when spirochetes in the tick's saliva or excreta enter the skin rapidly as the tick bites. Congenital borreliosis has also been reported.
The mortality rate is generally < 5% with treatment but may be considerably higher in very young, pregnant, old, malnourished, or debilitated people or during epidemics of louse-borne fever.
Symptoms and Signs
Because the tick feeds transiently and painlessly at night, most patients do not report a history of tick bite but may report an overnight exposure to caves or rustic dwellings. When present, louse infestation is usually obvious.
The incubation period ranges from 3 to 11 days (median, 6 days). Sudden chills mark the onset, followed by high fever, tachycardia, severe headache, vomiting, muscle and joint pain, and often delirium. An erythematous macular or purpuric rash may appear early over the trunk and extremities. Conjunctival, subcutaneous, or submucous hemorrhages may be present. Fever remains high for 3 to 5 days, then clears abruptly, indicating a turning point in the disease. The duration of illness ranges from 1 to 54 days (median, 18 days). Later in the several weeks' course of the disease, jaundice, hepatomegaly, splenomegaly, myocarditis, and heart failure may occur, especially in louse-borne disease. Other symptoms may include ophthalmitis, iridocyclitis, exacerbation of asthma, and erythema multiforme. Meningismus is rare. Spontaneous abortion can occur.
Patients are usually asymptomatic for several days to ≥ 1 wk between the initial episode and the first relapse. Relapses, related to the cyclic development of the parasites, occur with a sudden return of fever and often arthralgia and all the former symptoms and signs. Jaundice is more common during relapse. The illness clears as before, but 2 to 10 similar episodes may follow at intervals of 1 to 2 wk. The episodes become progressively less severe, and patients eventually recover as they develop immunity.
Diagnosis
The diagnosis is suggested by recurrent fever and confirmed by visualization of spirochetes in the blood during a febrile episode. The spirochetes may be seen on darkfield examination or Wright's- or Giemsa-stained thick and thin blood smears. (Acridine orange stain for examining blood or tissue is more sensitive than Wright's or Giemsa stain.) Serologic tests are unreliable. Mild polymorphonuclear leukocytosis may occur. Serologic tests for syphilis and Lyme disease may be falsely positive.
Differential diagnosis includes Lyme arthritis, malaria, dengue, yellow fever, leptospirosis, typhus, influenza, and enteric fevers.
Treatment
In relapsing fever transmitted by ticks, tetracycline or erythromycin 500 mg po q 6 h is given for 5 to 10 days. A single 500-mg oral dose of either drug cures louse-transmitted fever. Doxycycline 100 mg po q 12 h for 5 to 10 days is also effective. Children < 8 yr are given erythromycin estolate 10 mg/kg po tid. When vomiting or severe disease precludes oral administration, doxycycline 1 to 2 mg/kg may be given IV q 12 to 24 h to children > 8 yr. Children < 8 yr are given penicillin G 25,000 units/kg IV q 6 h.
Therapy should be started early during fever. A Jarisch-Herxheimer reaction may occur within 2 h of starting therapy. Severity of the Jarisch-Herxheimer reaction may be lessened by giving acetaminophen 650 mg po 2 h before and 2 h after the first dose of doxycycline or erythromycin.
Dehydration and electrolyte imbalance should be corrected with parenteral fluids. Acetaminophen with oxycodone or hydrocodone may be used for severe headache. Nausea and vomiting should be treated with prochlorperazine 5 to 10 mg po or IM once/day to qid. If heart failure occurs, specific therapy is indicated.
Last full review/revision August 2009 by Burke A. Cunha, MD
Content last modified August 2009
| |
|
