A number of researchers have suggested that gastrointestinal disease may be due to infection, stress, or a combination of both, but disentangling these causes can be difficult, as classical scientific method of controlled experimentation is not feasible with human subjects. Researchers at the University of Malaysia have reported results from an animal study that was able to shed some light on the topic. Three-week old Wistar rats were divided into four groups, mainly and subjected to (a) no stress or infection (control); (b) stress alone; (c) infection with Blastocystis alone; and (d) both stress and infection with Blastocystis. The study reported that while the stress group gained more weight, there were no significant immunological differences between the stress and control group. The group infected with Blastocystis showed lower levels of oxidants. Additionally, infection with Blastocystis was associated with lower peripheral blood mononuclear cell counts. The group exposed to stress and Blastocystis infection had higher levels of parasite count in stool samples, serum IgE, and oxidized protein compared to the Blastocystis group alone. The full paper is available from PLOS-One.