Gross and microscopic pathological changes associated with parasitic infection in European eel (Anguilla anguilla, Linnaeus 1758)

The gross pathological and histopathological changes associated with parasitic infection in the European eel (Anguilla anguilla Linnaeus, 1758) was investigated. A total of 65 eels collected from three sampling localities in Eastern Delta, Egypt were examined over the period of January-May 2008. The fish were subjected to standard procedures for parasitological and pathological examinations. Overall, 22 (33.8\%) of the 65 fish examined were found to have parasitic infections. The eels harbored a total of six parasite species; among them, the nematode Anguillicoloides crassus was the most prevalent species (10.7\%), followed by the Monogenea Pseudodactylogyrus anguillae (7.7\%) and Dactylogyrus species (6.1\%), the ciliate Trichodinella epizootica (4.6\%), the Myxozoa Myxidium giardi (3.1\%), and the cestode Proteocephalus macrocephalus (1.5\%). Affected fish showed varying levels of tissue damage and pathological alterations including mild to severe degenerative, necrotic, and inflammatory changes in the affected organs.