Protozoan parasites are unicellular eukaryotic organisms that share many structural and functional characteristics with mammalian cells. Some species infect humans and animals, causing a wide range of diseases that are of major concern in both human and veterinary medicine. Currently, effective and safe treatments or vaccines are lacking for most protozoan infections. Many pathogenic protozoa invade host cells by recognizing glycan receptors on the cell membrane, such as sialic acid and heparan sulfate. Supplementation of these glycan molecules has been shown to inhibit cell invasion in species, such as Plasmodium, Toxoplasma, Babesia, and Cryptosporidium (Fig. 68.1) [1–3]. Understanding the mechanisms by which protozoan molecules recognize host cell glycans is expected to facilitate the development of new therapeutic drugs and vaccines [4].