Detection of Bartonella quintana Infection among the Homeless Population in Tokyo, Japan, from 2013–2015

Several outbreaks of trench fever caused by Bartonella quintana occurred in soldiers during World Wars I and II. Although trench fever cases have been decreasing worldwide, the disease was reported among the homeless population in developing and developed countries. The current prevalence of B. quintana infection in Japan is unclear. Blood and body louse (Pediculus humanus humanus) samples were obtained from homeless inpatients with body lice during emergency hospitalization in Tokyo from January 2013 to March 2015. Patients were tested for B. quintana infections using the culture method, polymerase chain reaction, and indirect immunofluorescence assay (IFA). Among the 29 patients tested, the presence of Bartonella spp. was confirmed by genomic sequencing of DNA extracted from two samples from blood culture performed for 15 out of 29 patients and from body louse samples of 20 patients (69%). Immunoglobulin G against B. quintana was detected in 10 patients (34.5%) at a cut-off titer of 1:256 in IFA. B. quintana infection was detected in samples obtained between 2013 and 2015 in Tokyo and needs to be on the list of differential diagnoses performed for febrile homeless individuals.