infectious diseases
Relapsing Fever
Introduction
Relapsing fever is a recurring febrile disease caused by several species of the spirocheteBorreliaand 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 atetracycline,doxycycline,erythromycin, orprocaine penicillin G. Spirochetes are distinguished by the helical shape of the bacteria. Pathogenic spirochetes includeTreponema,Leptospira, andBorrelia. BothTreponemaandLeptospiraare too thin to be seen using brightfield microscopy but are clearly seen using darkfield or phase microscopy.Borreliaare thicker and can also be stained and seen using brightfield microscopy. The insect vector for relapsing fever may be the Body lice or certain ticks, depending on geographic location. in saliva or feces ( General reference ). If the louse is crushed on a new host, Tick-borne relapsing fevercan be transmitted by soft-bodied ticks of the genusOrnithodorosor hard-bodiedIxodes scapularisticks. Tick-borne relapsing fever transmitted by soft-bodied ticks involves one of severalBorreliaspecies and is 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. 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. Infection is more likely to be acquired by people sleeping in rodent-infested cabins in the mountains and has also been associated with spelunking. is also the vector for Lyme disease, tick-borne relapsing fever transmitted by this tick occurs in the same Epidemiology . Coinfection with other Borreliahas also been rarely transmitted by blood transfusion. 