Fig. 1

Anatomy of Nasal cavity of chicken. a The evaluation of IBDV’s replication efficiency with different oral or nasal inoculation via qRT-PCR IBDV mRNA expression. b Anatomical structure of nasal cavity from chicken through a vertical section, and a transverse sketch of two cross-sections (I and II) from chicken’s nasal cavity. (a) concha nasalis rostralis, (b) optic nerve of nervus trigeminus, (c) nasal septum, (d) concha nasalis media, (e) infraorbital sinus, (f) inferior nasal meatus, (g) nasal meatus, (h) maxillary nerve of nervi trigeminus, and (i) vertical lamella of nostril. c Hematoxylin & Eosin (HE) stained panoramic cross-section I and II of chicken’s nasal cavity. Diffuse lymphoid follicle and Nasal-associated lymphoid tissues (NALT) are shown in the black boxes located at concha nasalis media and distributed at the dorsal side of choanal cleft and nasal septum. d Immunohistochemistry (IHC) staining of cross-section I and II showing the distribution pattern of IBDV VP2 positive cells at follicle-associated epithelium (FAE) and NALT of chicken’s nasal cavity. The number of VP2 positive cells on FAE or NALT were counted at 1hpi, 3hpi, and 12hpi near to concha nasalis rostralis, on the optic nerve of nervus trigeminus and concha nasalis media. The IBDV VP2 positive cells in different parts at different times were counted in four random fields (40 ×) from three cross-sections. The scale bar represents 1 mm for whole nasal panoramic cross-sections, 40× and 100× for all other fields. All data shown are the mean results from three independent experiments