Fig. 2.

Histopathological sections of the trachea from SPF chicks challenged and euthanized at 42 and 47 days of age, respectively (Exp. 1). (A) Trachea from unvaccinated bird challenged with M-41 (NONVAC/M41), showing intense inflammatory infiltrate, vascular congestion, hyperplasia, loss of preservation of cilia, glands, and pseudostratified epithelial structure. (B) Trachea from vaccinated bird challenged with M-41 (VAC/M41) revealing complete preservation of cilia, glands, and epithelia. (C) and (D) Tracheas from unvaccinated (NONVAC/PR03) and vaccinated birds (VAC/PR03) challenged with IBVPR03, respectively, showing complete preservation of trachea structures with no presence of inflammatory infiltrate. H&E. Bar = 50 μm (A, B) and 100 μm (C, D)