An acute infectious disease characterized by recurring fever. It is caused by spirochetes of the genus Borrelia and transmitted by the body louse (Pediculus humanus humanus) and by ticks of the genus Ornithodoros.

Louse-borne relapsing fever, caused by Borrelia recurrentis, is typically epidemic. Epidemics, once widespread on all continents, are rare but still occur in certain parts of South America, Africa, and Asia. Tick-borne relapsing fevers are endemic. They are more widely distributed throughout the Eastern and Western hemispheres. At least 15 species of Borrelia have been recognized as causative agents.

After incubation of 2–10 days, the initial attack begins abruptly with chills, high fever, headache, and pains in muscles and joints, and lasts 2–8 days, ending by crisis. A remission period of 3– 10 days is followed by a relapse similar to the initial attack but milder. There may be 4–5 relapses, although occasionally 10 or more have been recorded. Mortality varies from 2 to 5% but may be considerably higher during epidemics.

Chlortetracycline is the most effective antibiotic drug, but penicillin, oxytetracycline, and streptomycin also have therapeutic value.

The best way to prevent relapsing fever is to control louse and tick populations with effective insecticides and acaricides. Medical bacteriology Pediculosis