Caracterização morfológica e molecular de Eurytrema coelomaticum (Digenea: Dicrocoeliidae) recuperados de bovinos do estado de Minas Gerais, Brasil

Abstract

Eurytrematosis is a bovine helminthiasis with veterinary impact, caused by species of the genus Eurytrema that lodge in the pancreas and pancreatic ducts. The infection can trigger pancreatitis, cachexia and, consequently, reduced productivity. Morphological and molecular data of the parasite show that the species Eurytrema coelomaticum is prevalent in Brazil, but there is little additional and updated information about the taxonomy of these helminths recovered from cattle in the southeastern region of the country. In the present work, several taxonomic characters of specimens obtained from the Minas Gerais state were reviewed. For this, we used histology, light (brightfield and confocal) and scanning electron microscopy, including cryofracture, and molecular analysis, in order to aggregate information regarding the partial sequence of the 18S rRNA genes and for the first time Cytochrome oxidase (cox1) was used as a molecular marker. In the morphometric results, we suggest that the taxonomic parameters that should be used in the identification of the species E. coelomaticum, are: the ratio of the width of the oral sucker/width of the ventral sucker (0.66-1.4), the relation of the length/width of eggs (1.38-1.83), length (0.041-0.050 mm) and width of eggs (0.025-0.030 mm). Because of the result of the morphological analysis, it was possible to detail the helminth's body surface, in addition to characterizing the complex organization of the sub tegument muscle fibers, the suckers and pharynx; the organization of the reproductive systems organs; and, by scanning electron microscopy, we showed the presence of papillae on the dorsal surface of the parasite anterior region. In phylogenetic analysis, we reveal that the isolates of this study form a cluster with the E. coelomaticum sequences deposited in the GenBank. It was also possible to highlight that E. coelomaticum has greater genetic similarity to E. pancreaticum compared to E. cladorchis. Our results reinforce that the integrative taxonomy, based on the combination of several techniques of microscopy and molecular biology, provides to the helminthological systematics more solid data to differentiate, among other groups, digenetic trematodes, generating a complementarity of data that cannot be provided by an isolated technique. We conclude that the application of integrative taxonomy in E. coelomaticum contributed to inserting new morphometric, morphological and molecular criteria, expanding the understanding of this species in Brazil.