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...