RESUMEN
Paramphistomiasis, a trematode infectious disease in ruminants, has been neglected but has recently emerged as an important cause of productivity loss. The small intestine of slaughtered sheep was collected weekly from abattoirs (Kermanshah, Sanandaj, Tabriz and Urmia Slaughterhouses) to monitoring the seasonal occurrence of Paramphistomosis, 2,421 sheep carcasses (743 male (30.69 %) and 1,678 female (69.31 %)) were examined, out of which 0.041 % were positive for Paramphistomum infestation. Furthermore, upon evaluation Paramphistomum termatodes, Gastrothylax crumenifer and Cotylophoron detected as well. Overall, the small intestinal infestation by such parasite was 0.041 % which contained hyperemia, severe congestion and haemorrhage. The highest infection in the sheep infected with Paramphistomum spp. was found during the summer (July to August) (6.7, 2 %) and followed by the autumn seasons (November to October) (3.8, 2.3 %). Microscopic study of the small intestine revealed dilatation of intestinal glands, destruction of superficial glands, replacement of fibrin, diffuse infiltration of inflammatory cells and fibrinonecrotic enteritis. Other changes as congestion hemorrhage and nodules of Ostertagia were observed in total examination of small intestines. According to statistical analysis by SPSS software and Chi square test revealed that there is significant difference between pathologic changes, seasons and ecological situations of the region (p < 0.05). There was no significant difference between age, gender and sample pH of examined sheep (p > 0.05).According to the results of pathologic changes of sheep small intestines, preventive measurements in the area should be taken to decrease the damages, so applying a parasitic control program is recommended.