g. Figure 3b). The degranulation

of MCs and neutrophils was characterized by free granules that were frequently seen close to the capilliform filitriches (Figure 4b) or adjacent to and/or between the coniform spinitriches of the scolex (Figure 4b) (see 39 for cestode microtriche terminology). In some grids, because of the plane of the section, the free granules from neutrophils and MCs were found in contact with the scolex tegument (respectively, Figure 4c,d). Several glandular cytons within the syncytial tegument along the anterior and lateral parts of the M. wageneri scolex were observed (not shown). No discharge from these glands or the presence of an adhesive layer in the interface region between the tench intestine and the tapeworm was evident. Cyprinids are the main group of freshwater fish that have a global importance as a source of food in many PD-0332991 concentration countries. The study of

disease in cyprinids held in captivity and in semi-wild stocks is essential for Public Health Authority. The pathological alterations to the intestine of cyprinids due to cestodes have been detailed in several PD0325901 in vitro papers (3,4,40). Among gross effects of tapeworms on fish hosts, intestinal occlusion and rupture are infrequent and extreme consequences of cestode infection (41). Such phenomena are among the most serious impacts induced by intestinal tapeworms, which have been associated with debilitation, nutritional disturbance and even the death of heavily parasitized fish (42). Generally, infection of the gastrointestinal tract by parasites has detrimental effects on digestion function (5,7).

Most intestinal pathology associated with tapeworm infections results from the deep penetration of the scolex into the gut wall (43). The organs used by intestinal helminths during the process of attachment to their host’s gut frequently induces inflammation of the alimentary canal (5,10). This is the case in M. wageneri that induces marked pathological changes, penetrating the muscularis layer (41, current study), causing a significant inflammatory Resveratrol response in all layers of the intestine in both light and heavy infections. M. wageneri is a caryophyllidean cestode and it was reported that the tegumentary glands of this group of tapeworms release neutral glycoproteins which protect the parasite against host cellular responses (44). This interpretation, however, does not appear plausible given that no discharge from these glands nor the presence of an adhesive layer between the tench intestine and M. wageneri was evident in the material studied here. The presence of abundant immune cells at the site of M. wageneri attachment and presence of free granules discharged from MCs and neutrophils in close contact with the scolex microtriches rule out earlier interpretations (44). Rodlet cells (23) and two type of granulocytes, MCs (23,24,30,45) and neutrophils (20,31), have been repeatedly shown to play an essential role in the immune system of fish.