Excretion of living Borrelia recurrentis in feces of infected human body

Louse-borne relapsing fever (LBRF), caused by Borrelia recurrentis, is 1 of the most dangerous arthropod-borne diseases. Infection is thought to occur through louse crushing. Lice feces have not been shown to contain living borreliae. We infected 800 body lice by feeding them on a rabbit made spirochetemic by the injection of borreliae. The life span of infected lice was not shortened. Once infected, lice remained infected62 10 for life but did not transmit borreliae to their progeny or to nurse rabbits. B. recurrentis infection was observed throughout lice and spread into hemolymph on day 5 after infection. We describe 2 unprecedented phenomena. In hemolymph, B. recurrentis formed clumps of aggregated borreliae. Using immunofluorescence assay, trans-mission electron microscopy, and culture, we detected borreliae excreted in lice feces beginning on day 14 after infection. We conclude that, similar to epidemic typhus and trench fever, transmission of LBRF may be caused by lice feces. Borrelia recurrentis, a slender microaerophilic spiro-chete, is the etiologic agent of louse-borne relapsing fever (LBRF; also known as “epidemic relapsing fever”). This disease can cause large outbreaks under certain conditions. In the 20th century, at least 7 major epi