Comparative study of X-ray computerised tomography and conventional X-ray methods in diagnosis of swimbladder infection in eels caused by Anguillicola crassus

Abstract

To date, swimbladder lesions due to Anguillicola crassus infection of the European eel Anguilla anguilla have so far been studied only by conventional X-ray methods. This is the first study to report the use of computerised tomography (CT) for studying lesions induced by anguillicolosis. Of 50 eels caught by electrofishery from Lake Balaton, Hungary, in autumn 2002 and pre-selected by a conventional X-ray method, 22 specimens were examined with a Siemens Somatom Plus S40 spiral CT scanner. Tomograms, radiographs and photographs of 5 of these, showing anguillicolosis-induced swimbladder lesions of varying severity, are presented. Computerised tomograms provide information on the inner structure, air content and wall thickness of the swimbladder as well as on the number of worms it contains. When the swimbladder is not severely affected or not completely filled with worms, computerised tomography provides adequate data on the shape of the swimbladder, thickness of the swimbladder wall and the location of worms in the lumen. However, in more severe cases, i.e. when the swimbladder is tightly packed with worms or contains no air as a result of wall-thickening, this method fails to determine the number and location of helminths or the thickness of the swimbladder wall.