Pathologic Features of Chronic Pneumonia in Pigs with Experimentally Induced African Swine Fever

Abstract

SUMMARY Chronic pneumonia developed in 14 pigs inoculated with an attenuated strain of African swine fever ( asf ) virus. The pathogenesis of the pneumonia was as follows: (1) Interalveolar septums became thickened by accumulation of lymphocytes and monocytes; (2) lung developed focal areas of lymphocytes and macrophages; (3) necrosis began abruptly in these foci, beginning with the cells in the alveolar lumens, developing in centrifugal direction, and eventually affecting all structures in its path; (4) necrotic tissue became calcified; and (5) a mantle of mononuclear cells (including plasma cells) and fibrous tissue formed around the necrotic area. Viremia occurred in the 14 pigs at postinoculation day ( pid ) 14, and precipitating antibody was increased significantly at pid 58.