RESUMO
Three groups of animals, each was orally infected with Cryptosporidium parvum oocysts, Enterocytozoon bieneusi spores or Cyclospora cayetanensis oocysts, were included in this study. At the time peak of colonization of infected animals, each group and its corresponding control were infused orally with radioactive isotope. Gastric emptying of isotope was significantly greater in infected compared with the controls in both fasted and fed states to determine the effect of each parasite on the contractility of longitudinal and circular muscle. Isometric tension of jejunal segments was recorded. The development of active tension with stretch and the dose-response curve were significantly increased in the longitudinal muscle of the infected animals compared with the controls. The circular smooth muscle did not show an increase in contractility. The results suggested that an altered gastrointestinal transit and smooth muscle contractility may be involved in the intestinal protozoa infections pathophysiology