Comparison of normal and mycoplasmal infraorbital sinus demonstrating the serious nature of pathology in M. gallisepticum -infected birds. Figure 3A: The infraorbital sinus of a partridge from the control group. The sinus is lined with a simple columnar epithelium (1). The sinus is surrounded by adipose tissue (2). H&E stain.
Figure 3B: The infraorbital sinus of a partridge infected with M. gallisepticum. The sinus is richly filled with a dense purulent exudate (1). The epithelium is mildly hyperplastic and the lamina propria is focally infiltrated by lymphocytes and plasma cells (2). H&E stain.