The present study was done from winter 2003 until spring 2004. Faecal Samples(n=400) were collected from calves and cattle in four age groups:0-6,7-12,13-24 months and 2-10 years old.Sample were stained by modified Ziel-Nelson method and oocytes of cryptosporidium were diagnosed on the basis of their sporozoiets. Infection rate was equal amomg animals during all seasons. Adult cattle had the highest infection rate in the healthy ones (23.75%). on the other hand, the highest prevalence rate of infection in the diarrheic animals was seen in the calves. While bovine cryptosporidiosis accompanying is with diarrhea in the <6 months of age, it has not any clinical signs in the adult ones.The present animals in Khorram-Abad(17.5%) were infected.
Key words: Cryptosporidium, diarrhea, children, calf, cattle.