Fig 4. S. Typhimurium 4/74 caused more severe histopathological changes in spleen, liver and caeca of inbred chickens than D23580.

Scores (0–4) based in histopathology score system used in Parsons et al, 2013 [3]. The histopathological tissue changes were semi-quantitatively measured using a grading scale ranging from 0 (no change) to 4 (severe damage to the tissue). Data is represented as a heatmap showing the histopathology score as a colour gradient by percent of birds. Statistical modelling showed that strain 4/74 was associated with an average increase of 0.22 relative to D23580 in the tissue histopathology scoring system (P < 0.001, S9–S11 Tables).