infectious diseases
Relapsing Fever
Symptoms and Signs of Relapsing Fever
Because the soft ticks of the genusOrnithodorosfeed transiently and painlessly at night and do not remain attached for a long time, 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). The clinical manifestations of tick-borne and louse-borne relapsing fever are very similar. Symptoms correspond to the level of bacteremia and, after several days, resolve whenBorreliaare cleared from the blood. Bacteremia and symptoms then return after a 1-week afebrile period. Symptoms are less severe with each subsequent return. A single relapse characterizes louse-borne relapsing fever, and up to 10 relapses may occur in tick-borne relapsing fever. Sudden chills mark the onset, followed by high fever, tachycardia, severe headache, nausea, vomiting, muscle and joint pain, and often delirium. An eschar may be present at the site of the tick bite. 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. Neurologic complications (eg, meningitis, meningoencephalitis, radiculomyelitis) may occur; they are more common in tick-borne relapsing fever. Spontaneous abortion can occur. Patients are usually asymptomatic for several days to≥1 week 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 weeks. The episodes become progressively less severe, and patients eventually recover as they develop immunity. 