So far, data has been mostly descriptive, and future research will need to address in particular: (1) how host circadian clocks and rhythms impact the initiation and outcome of parasitic infections; (2) the mechanisms involved in the effects of the parasites on host behavior and cellular functions; (3) the parasite-intrinsic rhythms and the clock mechanisms that underlie them. The gene discussed is CLOCK; the disease is parasitic infectious disease.