Bartonella quintana Infection in Canada: A Retrospective Laboratory Study and Systematic Review of the Literature.

Background:Bartonella quintana is a body-louse-borne bacterium. Canadian B. quintana disease has been reported primarily in populations experiencing homelessness and in Indigenous communities with limited access to water. We sought to understand the epidemiology of B. quintana in Canada. Methods: This study combined an analysis of laboratory data from Canada's National Microbiology Laboratory (NML) with a systematic review of the literature. Laboratory data included quantitative polymerase chain reaction (qPCR) cycle threshold values and indirect immunofluorescent antibody titers with the year and province of the sample acquisition. For the systematic review, we searched PubMed, Scopus, Embase, and Web of Science for articles published before 15 July 2024, with terms related to B. quintana in Canada. Results: Thirty-three individuals with qPCR-positive B. quintana were documented in seven provinces and one territory. The number of cases increased over time (p-value = 0.005), with the greatest number of cases being reported in 2022 and 2023. The percent positivity for the B. quintana qPCR performed at the NML increased over time (p-value = 0.036). The median immunoglobulin G titer demonstrated a sustained increase starting in 2017. The systematic review identified fourteen individuals with qPCR-positive B. quintana (none had a qPCR performed at the NML) and seven probable cases of B. quintana disease. Four of these twenty-one individuals from the systematic review died (19%). All fatalities were attributed to endocarditis. Conclusions: The detection of B. quintana disease in seven provinces and one territory suggests that B. quintana has a national distribution. B. quintana disease is increasingly diagnosed in Canada, indicating ongoing transmission across geographic settings.