Freshwater Amoebiasis – Histopathology

Freshwater Amoebiasis - Histopathology

Fish affected with branchial amoebiasis, have marked epithelial fusion and hyperplasia, leading often to loss of normal gill architecture, with obliteration of interlamellar spaces. Several species are involved, some of which invade the lamellar epithelium. Trophozoites can therefore be seen in small groups within the branchial epithelium as well as on the surface. Several diagnostic methods can be used for the detection of amoebae, including whole mounts of fresh gills, histopathology, isolation and culture, in situ hybridization (ISH), electron microscopy and indirect immunofluorescence. Differential diagnoses...

Freshwater Amoebiasis (Nodular Gill Disease) – Gross Pathology

O. mykiss, white spots on gills consistent with severe lamellar hyperplasia.

Amoebiasis in freshwater is a particular problem in salmonids and is reported worldwide. It is sometimes given the name nodular gill disease (NGD), based on the marked and grossly observable epithelial hyperplasia. In Chile the first report was in February 2017, in rainbow trout in the Araucanía region. Different genera of freshwater amoebae have been described for different fish species. Affected species include Atlantic salmon (Salmo salar), Chinook salmon (Oncorhynchus tshawytscha), rainbow trout (Oncorhynchus mykiss), Coho salmon (Oncorhynchus kisutch), blue tilapia (Sarotherodon aureus), golden carp...