Effect of Nanophyetus salmincola and Bacterial Co-Infection on Mortality of Juvenile Chinook Salmon.

The freshwater trematode Nanophyetus salmincola has been demonstrated to impair salmonid immune function and resistance to the marine pathogen Vibrio anguillarum, potentially resulting in ocean mortality. We examined whether infection by the parasite N. salmincola similarly increases mortality of juvenile Chinook Salmon Oncorhynchus tshawytscha when they are exposed to the freshwater pathogens Flavobacterium columnare or Aeromonas salmonicida, two bacteria that juvenile salmonids might encounter during their migration to the marine environment.

Kinetics of viral load and erythrocytic inclusion body formation in Pacific herring artificially infected with erythrocytic necrosis virus.

Viral erythrocytic necrosis (VEN) is a condition that affects marine and anadromous fish species, including herrings and salmonids, in the Atlantic and Pacific oceans. Infection is frequently associated with severe anemia and causes episodic mortality among wild and hatchery fish when accompanied by additional stressors; VEN can be presumptively diagnosed by (1) light microscopic identification of a single characteristic-a round, magenta-colored, 0.8-μm-diameter inclusion body (IB) within the cytoplasm of erythrocytes and their precursors on Giemsa-stained blood films; or (2) observation (via transmission electron microscopy [TEM]) of the causative iridovirus, erythrocytic necrosis virus (ENV), within erythrocytes or their precursors.