The pathogenesis of bluetongue in sheep: a study by immunofluorescence and histopathology

Abstract

The pathogenesis of bluetongue in sheep was studied by clinical and gross observations, immunofluorescence, histopathologic, and serum-virus neutralization techniques. Sheep were killed during a 16 day postinoculation period to study the development of bluetongue disease. The sheep were killed at daily intervals, either as single sheep or in groups of two on each day following inoculation, in order to study the sequential development of the lesions of bluetongue. Immunofluorescent staining was used to detect bluetongue viral antigens in tissues of infected sheep from 3 to 16 days postinoculation. Bluetongue virus (BTV) was found to have an affinity for the endothelium, periendothelial cells, and pericytes of capillaries, precapillary arterioles, and venules. The concentration of antigen, as determined by immunofluorescence, was greatest in small vessels underlying stratified squamous epithelium, particularly that of oral mucous membranes, skin, and coronet of the hoof. The increased concentration of BTV in these vessels in comparison to similar vessels in other tissues was apparently related to lower temperatures in these structures since they are close to the body surface. Antigens of BTV were detected also in reticulo-endothelial cells of the lymph nodes. Antigen was not detected-in epithelial cells. ...