The disease is caused by Borrelia species (spirochetes). There are two distinct forms of this disease:
- Louse borne relapsing fever (LBRF): Body lice (Pediculus humanus) become infected with B. recurrentis by feeding on spirochetemic humans, the only reservoirs of infection. Humans become infected when an infected louce is crushed and their body fluids contaminate mucous membranes or breaks in the skin.
- Tick borne relapsing fever (TBRF): The ticks become infected by feeding on spirochetemic hosts (rats, mice, chipmunks, squirrels, rabbits, hares and humans). The spirochetes are transmitted by ticks to humans and animals via saliva and excretory fluids when the tick feeds.
Clinical manifestations of relapsing fever
The clinical manifestations of LBRF and TBRF are similar. The mean incubation period is 7 days, and the onset of illness is sudden, with fever, headache, shaking chills, sweats, myalgias, and arthralgias. The arthralgia of relapsing fever can be severe, involving small and large joints, but there is no evidence of arthritis. Dizziness, nausea, and vomiting are common. The fever is high from the first, with a usual temperature of 40?C (104?F); fever is most often irregular in pattern and is sometimes accompanied by delirium. Dissimated intravascular coagulation, hepatosplenomegaly & jaundice are possible complications. The fever occurs while the organism is circulating the blood. The organism then undergoes massive phagocytosis to be followed by relapse after 5 days with different antigen.
Diagnosis of relapsing fever
The diagnosis of relapsing fever is confirmed most easily by the detection of spirochetes in blood, bone marrow aspirates, or cerebrospinal fluid. Motile spirochetes can be seen when fresh blood is examined by dark-field microscopy.
Treatment of relapsing fever
Relapsing-fever types of borrelia are exquisitely sensitive to antibiotics. Treatment with either erythromycin, a tetracycline, chloramphenicol, or penicillin produces rapid clearance of spirochetes and a remission of symptoms.
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