Formation of parasitic nodules in the swimbladder and intestinal walls of the eel Anguilla anguilla due to infections with larval stages of Anguillicola crassus

The histopathological lesions caused by 3rd and 4th stage migrating larvae of Anguillicola crassus In the swunbladder and intestinal wall of eel were studled Some of the larvae were detectable in the oedematous connective tlssue of the swilnbladder subserosa and in the gas gland bvithout giving nse to a s~gnificant cellulal host reaction In some eel, tlssue proliferation consisting of epithelioid cells started around the migrating larvae In more advanced cases, the epitheliold cells around the larvae underwent necrosis in the deep layers of the granulation tissue glant cells we le formed, and the nodule became surrounded by a flbrous capsule In more chronlc cases the nodules contained necrotic larvae and amorphous cell debrls In the case of an enteric infection, a similar nodule formation was observed In the intestine The parasitic nodules bulging out the serosa of the intestinal wall towards the abdominal cavity occas~onally changed ~ n t o dbscesses (pustules) In anguillicolosis, cysts llned wlth epithelium and filled with serum also commonly occur in the swimbladder mucosa, however, these could not be brought lnto connection wlth larval migration KEY LVORDS: Histopathology . Anguillicola crassus Ee l . Larval stages . Nodules Pustules