Pathological and histopatnotogical studies of the swimbladder of eels Anguilla anguitla infected by Angutlticpta crassus (Nemafoda: Dracuncuioidea)

Abstract

The swimbladder lesions produced by Anguillicola crassus (Nematoda) infection, causing mass mortality among eels in Lake Balaton (Hungary) were studied by histological methods. In the initial phase of infection, no severe changes developed in the swimbladder wall despite the presence and intensive blood-sucking activity of worms that filled the lumen of the swimbladder. After disruption of the worms and primarily because of repeated reinfection by larvae, however, the wall of the swimblaader markedly thickened and showed degenerative, inflammatory and proliferative changes. Acute processes were characterized by epithelial hyperplasia and hyperaemia of the swimbladder wall. In cases of chronic swimbladder inflammation, oedema and hyperplasia of tissues of the tunica propria, submucosa and serosa could be observed, as well as granulomatoid infiltration by mononuclear cells and fibrinoid degeneration around the larvae