Morphogenesis of Enteric Lesions Induced by Group D Rotavirus in Ringneck Pheasant Chicks (Phasianus colchicus)

Eight day-old male and female ringneck pheasants (Phasianus colchicus) were inoculated with group D rotavirus and necropsied at 4, 7, and 11 days post-inoculation. The intestinal tracts were examined by light and electron microscopic and immunohisiochemical methods. By 4 days post-inoculation, 2/3 (66%) inoculated birds were stunted and had diarrhea 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 infiltrate of lymphocytes, plasma cells, and macrophages. Immunoreactivity to rotaviral antigen was localized to enterocytes on the tips of villi in the duodenum, jejunum, and proximal ileum. By 7 days post-inoculation, 3/3 (100%) inoculated birds had clinical signs and gross and microscopic changes similar to those at 4 days post-inoculation but more severe. Immunoreactivity was localized in enterocytes scattered along the sides of 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 nm in diameter) were present within dilated components of the cytocavitary network. Macrophages within the lamina propria contained phagocytosed remnants of necrotic virus-infected cells. By 11 days post-inoculation, birds did not have gross lesions, but 1/2 (50%) had mild crypt hyperplasia and an infiltrate of leukocytes in the lamina propria. Occasional enterocytes along the sides of 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 rotaviral infections in other species.