Effect of P. salmonis infection in SHK-1 cells treated with plasmas obtained from O. mykiss fed with diets supplemented with different concentrations of selenium. A Representative microphotographs of SHK-1 monolayer exposed to SSP1 or SSP5 in panoptic staining. Upper panels show uninfected cells, and lower panels show P. salmonis infected cells at 10 days post-infection (dpi) and selenium supplemented plasma (SSP) treatment. Red squares are indicative of P. salmonis containing vacuoles (PCVs), Bar = 20 μm. B SHK-1 cells treated and stained with hematoxylin–eosin. Six photographs were used to count infected cells with at least one per total cells on a field. C SHK-1 cells treated and stained with hematoxylin–eosin. Six photographs were used to count PCVs per total cells on a field represented in the right Y-axis (bars). In the left Y-axis, PCV’s area was represented (blue circles) (n = 6). D P. salmonis relative load (arbitrary units (AU); left axis, blue) (n = 6) and cell viability measured by SHK-1 Trypan blue staining (right axis, grey) (n = 10) in SSP1 or SSP5 treated/untreated and infected/uninfected cells. All determinations were performed when the control was in the detachment phase of infection. One-way ANOVA and Tukey multiple comparisons between all treatments were performed. Different letters represent significant differences (p-value < 0.05).