Replication of atypical ovine rotavirus in small intestine and cell culture.

Colostrum-deprived lambs experimentally infected with an atypical ovine rotavirus isolated from naturally scouring animals, and a naturally infected colostrum-deprived lamb, were examined by immunofluorescence and immunoperoxidase labelling, and electron microscopy. A hyperimmune serum to the virus was produced in a gnotobiotic lamb and used to demonstrate antigen in the villous epithelial cells of the small intestine from infected animals. Scanning and transmission electron microscopy of tissues from infected animals revealed giant multinucleate syncytia composed of fused epithelial cells. Infected cells contained intracytoplasmic virus particles which resembled group A rotaviruses in morphology and morphogenesis. Small numbers of infected cells in MA104 cultures inoculated with ovine atypical rotavirus could be detected by immunofluorescence but virus growth could not be maintained by passage. Virus particles were seen by thin-section electron microscopy but their morphology and morphogenesis were abnormal; they were each composed of a single electron-dense shell, with no core, and were associated with envelopes of smooth membrane rather than rough endoplasmic reticulum.