Molecular basis of pathogenesis of Apicomplexan parasites in humans and livestock. Apicomplexan parasites are a major cause of mortality and morbidity in humans and livestock. These intracellular parasites secrete proteins that act on host cell signaling pathways to create the niche in which they can replicate. In turn, host cells have intricate mechanisms to detect and combat these parasites. As a consequence these parasites and their hosts co-evolve, leading to variation in both host and parasite genomes and to the emergence of differences in parasite virulence and host resistance. I am interested in how the interactions between parasite and host can lead to disease with a special interest in the genetic basis for individual host differences in resistance and parasite differences in virulence. A major effort of my lab is to identify genes from a model apicomplexan parasite, Toxoplasma gondii, that mediate the modulation of the host cell and to characterize the proteins encoded by these Toxoplasma genes, their host cell interaction partners and their role in virulence and co-option of the host cell. We also study host genetic factors involved in resistance to Toxoplasma. We try and apply what we have learned from our work with Toxoplasma to veterinary diseases caused by other apicomplexan parasites such as Neospora spp. and Sarcocystis neurona.