Light and scanning electron microscopy of sporocysts of Eurytrema coelomaticum (Giard et Billet, 1892) Looss, 1907

Eurytrema coelomaticum: updated morphology of adult worms using advanced microscopy experiments

Eurytrema coelomaticum is a digenean flatworm of ruminants that is the causative agent of eurytrematosis, a disease of veterinary health concern. Although modern techniques of morphological analysis have provided new insights about the morphology and anatomy of parasitic helminths, most studies on E. coelomaticum adults are based on conventional light microscopy. In the present study, a combined approach using brightfield, fluorescence, confocal and scanning electron microscopies (SEMs), together with the cryofracture technique, have updated morphological data on E. coelomaticum recovered from cattle in Rio de Janeiro State, Brazil. Light microscopy confirmed the presence of several structures present in the current description, such as suckers, pharynx, oesophagus, intestinal bifurcation and the cirrus-sac. Fluorescence stereomicroscopy revealed for the first time the cubic crystal protein inclusions in the forebody, which were further detailed by confocal and SEMs. Confocal microscopy provided detailed information of the muscular architecture associated with the attachment structures (suckers), digestive system (pharynx and oesophagus), egg-forming complex (ovary, Mehlis' gland and Laurer's canal) and male reproductive system, which are similar to those found in other digenean flukes. SEM images of cryofractured parasites showed mucus and developing eggs within uterine loops. It was demonstrated that the combination of advanced tools generated complementary information, confirming the importance of experimental morphology in parasitology. Therefore, the knowledge of the adult structural organization of E. coelomaticum was improved and this work has contributed to propose new morphological criteria to evaluate the effects of antiparasitic drugs on flukes of medical and veterinary importance.

Histological description of Cercaria etgesii Shchenkov, 2017 daughter sporocysts (Trematoda: Pleurogenidae): compartmentalization of the brood cavity and germinal mass morphology

Morphology of the daughter sporocysts of Cercaria etgesii Shchenkov, 2017 (Pleurogenidae) has been described according to conventional histological techniques and subsequent 3D reconstruction with Bitplanelmaris® software. Novel data were obtained concerning the spatial organization of the brood cavity of Pleurogenidae daughter sporocysts. It was shown that the laminated structures of the endocyst are lining the brood cavity and carry out its compartmentalisation by formation of the chambers around developing and disintegrating embryos of cercariae. First description of the germinal mass of the Pleurogenidae daughter sporocysts is given. No mitoses in germinal mass were evident although apparent production of the cercariae embryos by the sporocysts take place. The analogous principle of daughter sporocysts morphofunctional organisation was noted for the studied representatives of closely related taxa of trematodes: Pleurogenidae (C. etgesii) and Microphallidae (Microphallus 'pygmaeus' group).

Relationship Between Pathological Findings and Cholinesterase Activity and Nitric Oxide Levels in Cattle Infected Naturally by Eurytrema coelomaticum

The aim of this study was to evaluate the role of butyrylcholinesterase (BChE) (in the serum and pancreas), acetylcholinesterase (AChE) (in the whole blood and pancreas) and nitric oxide (NO) (in the serum and pancreas) in cattle infected naturally by Eurytrema coelomaticum. Fifty-one cattle were studied, including 33 infected by E. coelomaticum and 18 uninfected animals. Significantly greater AChE activity was found in the pancreas of infected animals (P <0.01); however, these cattle had lower AChE activity in whole blood. BChE activity was greater in the sera of infected animals (P = 0.05), but was less in pancreatic samples. NO levels were significantly higher in the sera (P <0.05) and pancreas (P <0.001) of infected cattle compared with uninfected animals. A positive correlation was found between AChE activity in the pancreas and parasite load, but there was negative correlation between pancreatic BChE activity and parasitic load. Expression of AChE, BChE and NO is therefore linked to the inflammation caused by E. coelomaticum in cattle.