RESUMO
Cryptosporidium is an important protozoa that cause. diarrheal illness in humans and animals. In immunocompetent individuals, infection is usually self-limiting; but in immunocompromised patients infections which can be life threatening may develop. Cryptosporidium may account for 10 to 20% of the cases of diarrhea in immunocompromised patients living in developed countries and as much as 50% in underprivileged countries. Different strains of Cryptosporidium have been reported, and it is believed that strain characteristics are an important factor to be considered in strategic planning for the control of cryptosporidiosis disease. In this study human and animal isolates of Cryptosporidium oocysts were examined by PCR-RFLP for identifying strain variation in Isfahan. A total of 642 fecal samples of children under 5 years of age, imunocompromised patients and high risk persons and 480 rectal specimens of cows and calves were selected randomly in Isfahan. After identification of the samples contaminated with the parasites, oocysts were purified from these samples, and their DNA were extracted. These DNAs were use for detection of Cryptosporidium species using PCR-RFLP analysis of a 1750bp region of 18srRNA. Microscopic results showed that 4.7% of human samples and 6.2% of animal samples were contaminated with Cryptosporidium. 18s rRNA gene of all isolates were amplified by PCR, and 18s rRNA fragment size of all isolates were identical approximately 1750 bp. RFLP results showed that the samples were contaminated with C. parvum II, C. baileyi, C. serpentis, C. muris, C. wrairi and three new genotypes of Cryptosporidium. PCR-RFLP results indicated the occurrence of most strains of Cryptosporidium specially C. parvum. The results also imply extensive polymorphism in these parasites and the occurrence of mutant strains of it. Furthermore, the occurrence of animal species of the parasite in human samples shows the importance of animal-human cycle of it