Our research focuses on the sensory behaviors of parasitic and free-living nematodes, and lies at the interface of neurobiology and parasitology. The goals of our research are to understand how human-parasitic worms use sensory cues to locate hosts to infect, how sensory circuits of parasitic animals differ from those of free-living animals to enable parasitic behaviors, and how sensory microcircuits generate flexible outputs. We use the skin-penetrating gastrointestinal parasitic nematodes Strongyloides stercoralis and Strongyloides ratti, as well as the free-living nematode C. elegans, as model systems. S. stercoralis is a human parasite that infects ~600 million people worldwide. Our research addresses fundamental questions of sensory circuit function and evolution in the context of human parasitism. In addition, human-parasitic worms are a major cause of morbidity worldwide, and a better understanding of their sensory behaviors may enable the development of novel strategies for preventing or treating infections.