Smith, NicholasSinden, Robert ERamakrishnan, Chandra2022-11-102022-11-102235-2988http://hdl.handle.net/1885/278389For endoparasites, invasion of their hosts represents the greatest challenge to survival; for many it is the gut of the host/vector that present this barrier. Those barriers are increasingly being recognized as optimal targets for intervention strategies (Sinden, 2010; Smith et al., 2014; Sinden, 2017). The phylum Apicomplexa embraces thousands of species of parasites of vertebrates and invertebrates, many of major veterinary/medical importance including important agents of zoonoses. Whilst certain parasites are monoxenous (e.g., Eimeria, Cryptosporidium), others are heteroxenous (e.g. Plasmodium, Toxoplasma gondii) with distinct developmental pathways in each host. All Apicomplexans are thought to undergo critical developmental phases within intestinal tracts; thus, infection or transition of a gut is crucial for their survival. In this Research Topic, we present contributions on mechanisms of gut infection and traversal; the gut as a barrier to parasites; model systems for parasite development, and the impact of gut microbiota upon the infection process.NS is grateful for research support from the National Health and Medical Research Council (NHMRC) of the Australian Government (Project Grant GNT1128911).application/pdfen-AUCopyright © 2021 Smith, Sinden and Ramakrishnan.https://creativecommons.org/licenses/by/4.0/Apicomplexabarriergutimmune systemmicrobiotahostmodel system202110.3389/fcimb.2021.6805552021-11-28Creative Commons Attribution License