Proliferative Gill Disease (PGD) – Gross Pathology

PGD in Atlantic salmon showing white spots (clubbing), distal third of filaments.

PGD is a multifactorial worldwide disease with both infectious and non-infectious causes.  PGD leads to significant problems in Atlantic salmon (Salmo salar) and many other species. Among the infectious causes are viruses (Atlantic salmon paramyxovirus-ASPV, Salmon gill poxvirus-SGPV), bacteria (Tenacibaculum maritimus, Piscichlamydia salmones, Candidatus Clavochlamydia salmonis), parasites (Neoparamoeba perurans, Loma salmonae, Ichthyobodo spp., Trichodina sp.). Non-infectious causes include phytoplankton and zooplankton. Gross pathological changes include “clubbing”, in which thickened white areas of hyperplastic epithelium can be easily seen, mainly at the ends or distal third...

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...