Absence of Bartonella bacilliformis bacteraemia in asymptomatic individuals during an inter-outbreak period in an endemic Andean region

Background Carrión’s disease, caused by Bartonella bacilliformis , is endemic in the Andean valleys of Perú, Colombia, and Ecuador. The disease is believed to be transmitted by Lutzomyia verrucarum sandflies and typically occurs in seasonal outbreaks during periods of high vector activity. Although asymptomatic carriers are thought to maintain transmission between outbreaks, the presence of asymptomatic bacteraemia during inter-outbreak periods remains unclear. Methods We conducted a cross-sectional study in two rural Andean communities in the Áncash department of Perú during the inter-outbreak season (July 2019). Participants ≥ 1 year of age without clinical signs of Carrión’s disease were enrolled. Demographic data, medical history, and physical examination were recorded, and venous blood samples were collected for the culture of B. bacilliformis . Results Of 219 individuals invited, 197 provided samples; after exclusions for clotted or contaminated cultures, 177 were included in the analysis. The median age was 34 years (IQR, 25–49), and 64% of the participants were female. Eleven participants (6.2%) reported previous Oroya fever, and 50 (28.2%) had a history of verruga peruana. After 60 days of incubation, none of the 177 blood cultures were positive for B. bacilliformis . Thus, there were no asymptomatic bacteraemic individuals identified in our study during inter-outbreak period. Conclusions In this study, we did not detect bacteraemic asymptomatic individuals during the inter-outbreak period. Further studies in different regions and seasons with more sensitive molecular methods are warranted to clarify the role of asymptomatic carriers in the epidemiology of Carrión’s disease.