Ticks are vectors of various pathogens, resulting in severe human and animal health problems. The midgut of these arthropods constitutes the primary pathogen-vector interface, and microbial control in this organ may be mediated by the activity of antimicrobial peptides derived from the digestion of heme-containing proteins (hemocidins), lysozymes and defensins, as well as protease inhibitors and oxidative stress. Thus, vector competence in ticks is directly related with their immune system.