Gross findings in AvIDP-affected chickens. Compared to controls (A, C) a marked thickening of craniospinal nerve roots was recognized in all affected birds (B, D). A, B: Inspection of the ventral brain surface reveals severely enlarged maxillary (CN Vmax) and ophthalmic (CN Vopht) nerve branches. The oculomotor (CN III) and abducens (CN VI) nerve are also thickened to a lesser extend, and show a mild greyish discoloration. C, D: The dorsal view at the cervical intumescence between C13 and Th1 indicates severe enlargement of the dorsal rootlets (arrows) and the associated dorsal root ganglia (DRG). Affected ganglia (b) measure up to fourfold the diameters of unaffected control nerves (a). A, B: EB = eye ball; NO = optic nerve; P = Pons; scale bar = 1.0 cm. C, D: SC: spinal cord; scale bar 0.5 cm.