ABSTRACT
Differential diagnosis of two protozoan parasites Entamoeba histolytica and E. dispar is of great clinical and epidemiological importance, but except in the case of haematophagous trophozoites in acute dysentery, it is not possible to differentiate them by microscopy. The present study was carried out from February 2005 to July 2006 in order to determine the prevalence of E. histolytica and E. dispar in Gonbad City, by using a PCR method. Five hundred and sixty four fecal samples were collected from primary health care centers of Gonbad both urban and rural areas. The stool specimens were examined by light microscopy [Direct slide smear, Iodine wet mount, Formal-ether concentration and Trichrome staining] to distinguish E. histolytica/E. dispar complex and differentiate them from other non-pathogenic intestinal amoebae. The microscopy results of stool exams showed a frequency rate of 23 positive samples [4.07%] for cyst of E. histolytica/E. dispar complex. All the microscopy positive isolates appeared to be infected with cyst of E. histolytica/E. dispar complex were cultivated and maintained successfully in HSr + s medium for DNA extraction and identification by the PCR method. The PCR study showed that 16 isolates [69.56%] of the Entamoeba samples were E. dispar while 7 samples [30.43%] of those microscopy positive samples were not amplified and none of them showed E. histolytica pattern. High frequency rate of E. dispar in this study were in high agreement with the estimation rate of these entamoebas worldwide