Morphogenesis of enteric lesions induced by group D rotavirus in ringneck pheasant chicks (Phasianus colchicus)

The intestinal tracts of ringneck pheasant chicks inoculated with group D rotavirus at 8 days old, were examined PM by light and electron microscopy at 4, 7 or 11 after inoculation. After 4 days, 2 (66%) of 3 birds were stunted and had diarrhoea and dilated intestines. Intestinal villi were shortened, and many villous enterocytes were partially detached from the lamina propria. Crypts were hyperplastic, and the lamina propria contained a diffuse filtrate of lymphocytes, plasma cells and macrophages. Immunoreactivity to rotaviral antigen was localized to enterocytes on the tips of the villi in the duodenum, jejunum, and proximal ileum. By 7 days all of 3 inoculated birds had clinical signs and gross and microscopic changes similar, but more severe, to those of the 4 day group. Immunoreactivity was localized to the enterocytes scattered along the sides of the villi, in occasional crypt enterocytes, and within macrophages in the villous lamina propria. Ultrastructurally, infected enterocytes contained cytoplasmic aggregates of viroplasm with multiple viral core particles. Numerous mature virions (60-75 mm in diameter) were present within dilated components of the cytocavity network. Macrophages within the lamina propria contained phagocytosed remnants of necrotic virus-infected cells. By day 11, birds did not have gross lesions, but 1 (50%) of 2 had mild crypt hyperplasia and an infiltrate of leukocytes in the lamina propria. Occasional enterocytes along the sides of the villi and macrophages in the lamina propria were immunoreactive for viral antigen. Group D rotavirus is an enteropathogen in pheasants and causes intestinal lesions similar to those caused by enteric rotavirus infections in other species.