Biology (B.S.B.)

Document Type and Release Option

Thesis (open access)

Faculty Mentor

Lisa Brown


Fleas transmit numerous deadly and debilitating diseases, including the causative agents of murine typhus and plague. Because initial entry of these infectious agents occurs while blood feeding, the immune response in the flea gut is considered to be the first line of defense against invading microbes. However, relatively few studies have identified the flea immune molecules that effectively resist or limit infection in the gut. In other hematophagous insects, an immediate immune response to imbibed pathogens is the generation of reactive oxygen species (ROS). In this study, we utilized cat fleas (Ctenocephalides felis) to investigate whether natural infections with bacteria induce ROS synthesis in the flea gut, and whether production of ROS provides a defense mechanism against microbial colonization. Specifically, we assessed the generation of ROS via quantitative peroxide assays from fleas that were given uninfected and bacteria-infected blood meals. Additionally, we treated fleas with an antioxidant before infection with bacteria, and then measured the resultant bacterial load within each flea. Our data shows that ROS levels increase in response to infection in the flea gut, and that this increase helps to strengthen the flea immune response through the microbicidal activity of ROS. Overall, these data yield significant insight into how fleas interact with pathogens in their gut lumen, as well as the challenges faced by pathogens upon entering the flea host.