Ecological immunology of a flea vector (Ctenocephalides felis)

PROJECT SUMMARY/ABSTRACT Fleas are obligate vectors of bacterial pathogens that cause severe diseases in humans, including murine typhus and bubonic plague. To resist or limit infection, fleas possess an innate immune system that provides defense against microbial invasion and colonization. However, in their natural habitats, flea populations are made up of individuals that differ not only their genetic background, but also in regard to factors such as sex, age, diet, infection history, gut microbiota, and exposure to environmental stressors. These non-genetic factors have been shown to have important consequences on the outcome of infection in other disease vectors; yet, no studies to date have addressed the impact of these ecological parameters on flea immune responses. The proposed research aims to fill these knowledge gaps in flea ecological immunology, with the primary goals being to determine the intrinsic factors that affect the antibacterial response in adults, and to determine the effect of larval ecology on subsequent infections as adults. Specifically, we propose to compare the strength of immune defense mechanisms in adult cat fleas (Ctenocephalides felis) based on sex, age, and infection history (Specific Aim 1), as well as following larval exposure to food quantity, larval density, and insecticides (Specific Aim 2). This project will provide valuable insight into the variability of flea immunity under natural conditions, which can directly affect pathogen transmission dynamics and alter disease prevalence outcomes within a vector population. Data arising from this project could aid in the development of novel strategies to control the spread of flea-borne pathogens to humans.