Rotavirus infection in lambs: pathogenesis and pathology.

Experimental lamb rotavirus infections were studied by immunofluorescence, histopathology and electron microscopy of tissues from infected gnotobiotic lambs killed at intervals from the incubation period to recovery. The rotavirus was demonstrated by immunofluorescence only in epithelial cells of villi in the small and large intestine, and virus antigen was most abundant during the incubation period. An increased enterocyte turnover rate was suggested by the rapid movement of virus-infected cells to the villus tip, and this increase may be one of the basic pathogenic mechanisms of rotavirus infection. Principal histopathological changes were shortening of villi and sloughing of epithelial cells. These were greatest in the middle and posterior small intestine at the onset of diarrhoea, but regeneration occurred within a few hours. Virus morphology in tissues was similar to that reported in other species, and virus presence correlated well with histopathological change.