Location of Vibrio anguillarum in tissues of infected rainbow trout (Salmo gairdneri) using the fluorescent antibody technique.

Abstract

Rainbow trout (Salmo gairdneri) were injected intraperitoneally (IP) or waterborne infected with Vibrio anguillarum, strain LS-174. Every three hours for 48 h, three fish were sampled and fixed for histological examination. The progression of the infection and the fate of the invading pathogen was determined by staining sections with anti-V. anguillarum fluorescein-labeled rabbit immunoglobulin G (IgG). The tissue location of the pathogen in IP and waterborne infected fish was similar. In both cases the bacterium was initially sequestered in the spleen. Increase in the numbers of the bacterium occurred in the spleen followed by proliferation into the kidney. Death resulted from bacteremia with most tissues of the fish septic. Extensive necrosis of kidney, spleen, posterior intestine and liver was observed. The gills were congested with microorganisms and the epithelial cells destroyed. Extracellular bacterial antigen was observed in the musculature, kidney, liver, intestine and spleen. No phagocytosis by macrophages was observed.