Introduction: Dicrocoeliasis is a common disease of bile ducts and gallbladder of domestic and wild ruminants. This disease is caused by different species of dicrocoelium including Dicrocoelium dendriticum. The aim of this study was to identify pathological damages and molecular features associated with this parasite in ruminants.
Materials and Methods: In this cross-sectional study, 180 fresh adult D. dendriticum worms were collected from 45 infected livers of slaughtered cattle, sheep, and goats in three western provinces of Iran. After histopathological examination, a 963 bp fragment (28S rRNA [MRT1] gene) was amplified using Polymerase Chain Reaction (PCR). The amplified fragment was digested by Trul1 restriction enzyme to evaluate through Restriction Fragment Length Polymorphism (RFLP) method.
 Results: Based on histological examination, hyperplasia of mucosal glands and swelling of bile ducts of infected livers were observed. In all studied samples, a 963-bp fragment was produced by PCR. Based on PCR-RFLP, the PCR products were digested by Trul1 restriction enzyme producing four fragments (116 bp, 145 bp, 293 bp, and 409 bp) all of which were related to D. dendriticum. Sequencing of the obtained 28S rDNA fragments showed that all of them were completely similar, and comparing them with the Gene Bank sequences showed 97% to 100% similarity between homogeneous fragments. The obtained sequences were registered in the Gene Bank with the accession numbers of MT539114, MT539115, and MT539116.
Conclusion: According to the present study, D. dendriticum is the predominant parasite infecting ruminants in west of Iran.

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