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 a nd electron microscopic and immunohistochemical methods. By 4 days pos t-inoculation, 2/3 (66%) inoculated birds were stunted and had diarrhe a and dilated intestines. Intestinal villi were shortened, and many vi llous enterocytes were partially detached from the lamina propria. Cry pts were hyperplastic, and the lamina propria contained a diffuse infi ltrate of lymphocytes, plasma cells, and macrophages. Immunoreactivity to rotaviral antigen was localized to enterocytes on the tips of vill i in the duodenum, jejunum, and proximal ileum. By 7 days post-inocula tion, 3/3 (100%) inoculated birds had clinical signs and gross and mic roscopic 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 macrop hages in the villous lamina propria. Ultrastructurally, infected enter ocytes contained cytoplasmic aggregates of viroplasm with multiple vir al core particles. Numerous mature virions (60-75 nm in diameter) were present within dilated components of the cytocavitary network. Macrop hages within the lamina propria contained phagocytosed remnants of nec rotic virus-infected cells. By 11 days post-inoculation, birds did not have gross lesions, but 1/2 (50%) had mild crypt hyperplasia and an i nfiltrate of leukocytes in the lamina propria. Occasional enterocytes along the sides of villi and macrophages in the lamina propria were im munoreactive 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.