From Acquisition to Transmission: Revisiting Bartonella henselae Infection in the Cat Flea ( Ctenocephalides felis )

Background: The cat flea ( Ctenocephalides felis ) is the primary arthropod vector responsible for the transmission of Bartonella henselae , the etiologic agent of cat scratch disease. Although domestic cats serve as the principal reservoir host, maintaining long-term intraerythrocytic bacteremia, the spread of B. henselae within feline populations relies entirely on flea-mediated acquisition and transmission. Early work demonstrated that fleas readily acquire the bacterium while feeding on bacteremic cats and can subsequently infect naïve hosts; however, the underlying biological mechanisms remain only partially understood. Methods: This review synthesizes current knowledge of how B. henselae interacts with its flea vector, tracing the process from acquisition through midgut colonization, persistence, and transmission via contaminated feces. Conclusions: By integrating findings from artificial feeding systems, natural infection models, and recent advances in bacterial and vector biology, this review provides an updated assessment of the field and identifies key knowledge gaps that must be addressed to fully elucidate this vector–pathogen relationship.