Table 1. Histopathology scoring system for experimental avian salmonellosis.

Score	Tissue
	Ileum	Liver	Spleen
0	Normal	Normal	Normal
1	Small increase in heterophils and macrophage numbers in villi or underlying epithelium. No damage	Small increase in dispersed inflammatory cells	Small increase in dispersed inflammatory cells
2	Increased numbers of heterophils associated with epithelium and lamina propria. Slight thickening/edema of villi.	Increased numbers of inflammatory cells throughout tissue. Small foci of heterophils or macrophages	Increased numbers of inflammatory cells throughout tissue. Increased numbers of monocytic cells in red pulp
3	Extensive inflammatory influx. Thickening and/or flattening of villi.	Formation of small granuloma-like lesions. Extensive influx of inflammatory cells	Extensive influx of inflammatory cells. Increased lymphocyte and monocyte infiltration into white pulp. Some thickening of outer capsule
4	Extensive flattening/blunting of villi. Crypt hyperplasia.	Numerous small or large granuloma-like lesions. Small areas of necrotic damage	Massive cellular infiltration into both white and red pulp. Thickening of splenic capsule
5	Complete loss of villus structure	Large areas of necrotic damage leading to loss of organ structure.	Areas of necrotic damage with some loss of defined red and white pulp structure. Some loss of capsule integrity.

Scoring system based on histopathological descriptions for experimental infection of the chicken with S. Typhimurium (WIthanage et al., 2004, 2005) and S. Gallinarum (Wigley et al 2002).