We study various aspects of host-vector-pathogen interactions, with specific emphasis on tick-borne rickettsial organisms. In particular, we are deeply interested in identifying microbial and host genes important for the rickettsial intracellular lifecycles and determining the underlying molecular mechanisms associated with pathogenesis, tick transmission, and host immune evasion. Our four main focus areas are: 1) developing transposon mutant libraries for Rickettsia to identify genes important for rickettsial survival in mammalian hosts and arthropod vectors, 2) defining rickettsial immune evasion mechanisms in vascular endothelial cells, 3) monitoring native and invasive tick populations and documenting their interactions with tick-borne pathogens, and 4) understanding immunological responses to tick bites and pathogen transmission in patients.