RELAPSING FEVER : CLINICAL ASPECTS
After a mean incubation period of 7 days, massive spirochetemia develops, with high fever, rigors, severe headache, muscle pains, and weakness. The febrile period lasts about 1 week and terminates abruptly with the development of an adequate immune response. The disease relapses 2 to 4 days later, usually with less severity, but following the same general course. Tick-borne relapsing fever is usually limited to one or two relapses, but with louse-borne disease three or four may occur.
Louse-borne relapsing fever is more severe than tick-borne disease, possibly because of predisposing social conditions. Fatalities are rare in tick-borne disease but may be as high as 40% in untreated louse-borne fever. Fatal outcomes are due to myocarditis, cere-bral hemorrhage, and hepatic failure.
Diagnosis is readily made during the febrile period by Giemsa or Wright staining of blood smears. The appearance of the spirochete among the red cells is characteristic. Cultural and animal inoculation procedures are also used for recovery of the infecting organism.Serodiagnostic tests are unhelpful.
The disease responds well to tetracycline or erythromycin therapy, and single-dose treat- ment with these agents can be effective. Jarisch – Herxheimer reactions are particularly common in the treatment of relapsing fever perhaps because of the height of the spiro- chetemia at the time of antibiotic administration.
Prevention of tick-borne relapsing fever involves attention to deticking, insecticide treat-ment, and rodent control around habitations, such as mountain cabins, shown to be associ-ated with infection. Control of louse-borne relapsing fever involves delousing, particularly dusting of clothing with appropriate insecticides. Ultimately, improved hygiene stops out-breaks and prevents further occurrences.