Fig. (2) Histological pattern of lungs tissues of ferrets administered H7N3 LAIV or placebo after subsequent infection with wild type influenza H7N3 virus. Groups of six ferrets received two administration of 107 EID50 H7N3 LAIV intranasally in the volume 0.5 mL 28 days apart (Day 0 and D28). On day 42 the animals were challenged intranasally with 106 EID50 of wild type influenza virus A/mallard/Netherlands/12/2000 (H7N3) in volume of 0.1 mL. Control animals received 0.1 mL of physiological saline intranasally. Three animals from each group were euthanized on the day three after experimental challenge, and three remaining ferrets euthanized on the day 14. One lung from each sacrificed animal was used for histological analysis. Sections were stained with haematoxylin and eosin (200x magnification).