The increased number of documented human coccidian infections, including Cryptosporidium parvum, Cyclospora cayetanensis, Isospora belli, and Sarcocystis spp., that are often indistinguishable from other forms of community-acquired diarrhea, together with the possibility of treating some of them, suggests a need for proper diagnostic techniques to recover and identify these organisms

The increased number of documented human coccidian infections, including Cryptosporidium parvum, Cyclospora cayetanensis, Isospora belli, and Sarcocystis spp., that are often indistinguishable from other forms of community-acquired diarrhea, together with the possibility of treating some of them, suggests a need for proper diagnostic techniques to recover and identify these organisms.

Earlier, Cryptosporidium and Cystoisospora were assumed to be the causative agents of acute diarrhea in animals but recently have emerged as one of the leading causes of prolonged lifethreatening diarrhea in immunocompromised patients particularly in those with immune dysfunction like AIDS who may show severe intestinal injury, prolonged diarrhea, extreme weight loss, and generalized wasting. In contrast, healthy individuals commonly present with mild to moderate self-limiting diarrhea during the infective stage, besides asymptomatic infection can also occur.

Detection of coccidian parasites is mostly through microscopic observation using Kinyon's acid-fast stain. Although Sheather sugar flotation may result in increased concentration of the cysts, this method is cumbersome and does not lend itself to convenient incorporation within the routine concentration and staining procedures favored in most clinical laboratories. Any acid-fast stain will be taken up by cyst walls, but the time required to prepare and examine acid-fast stains on all stool samples received for routine parasitology would not be cost-effective unless the prevalence of coccidian parasites was shown to warrant such effort.

Inclusion Criteria:

• patients complaining of chronic diarrhea .

Exclusion Criteria:

• patients taking antibiotics within the previous four weeks, and anti-parasitic drugs within the previous two weeks.

patients from outpatient clinics in different hospitals in Sohag governorate complaining of diarrhea of any age and sex groups from different locations (cities and villages)