RESUMEN
An epidemiological study was done on 2 groups of children infected with watery diarrhea in some hospitals of Baghdad [Group 1: Immunocompetent outpatients. Group 2: Immunosuppressed inpatients]. Modified Cold Ziehl Neelsen stain was used in diagnosis. The whole oocysts antigen prepared after conduction of experimental infection in 2 calves by using isolated oocysts from children stool, and this prepared antigen was used in Indirect Fluorescent Antibody Technique [IFAT]. The percentage of infection in the 2 groups of outpatients and inpatients were 21 2% and 32% respectively, and there was a difference in percentage of infection between the 3 groups of children, the highest was 36.4% in group infected with leukemia and received chemical and radiotherapy. There was no significant difference noticed between the two sexes. The clinical signs of experimental infection began after 4 days and continued for 10 days. The oocysts appeared in IFAT as spherical in shape with clear walls and bright yellowish green color. There was no significant difference noticed between the 2 methods of diagnosis [stain and immunological test]