EXPERIMENTAL REPRODUCTION OF PNEUMONIA IN GNOTOBIOTIC PIGS WITH PORCINE RESPIRATORY CORONAVIRUS ISOLATE AR310

The pathogenicity of porcine respiratory coronavirus (PRCV) isolate AR 310 was determined for gnotobiotic pigs. PRCV-AR310 was isolated from the intestines of a nursery pig from a herd with endemic transmissible gastroenteritis. The AR310 isolate was plaque purified and cell cultu re propagated, passed once in a gnotobiotic pig, then used as inoculum for a gnotobiotic pig pathogenicity study. Eight pigs were inoculated oronasally with 2 x 10(6) plaque-forming units of PRCV-AR310. Eight p igs served as controls and received cell culture medium. Two pigs from each group were necropsied at 3, 5, 10, and 15 days postinoculation ( DPI). There was moderate multifocal to coalescing reddish tan consolid ation of 60% of the lung by 10 DPI. Microscopic examination revealed a necrotizing and proliferative bronchointerstitial pneumonia character ized by necrosis, squamous metaplasia, dysplasia, proliferation of air way epithelium, mononuclear cell infiltration of alveolar septa, mild type II pneumocyte proliferation, and lymphohistiocytic alveolar exuda tion. The microscopic lesions were mild by 3 DPI, moderate by 5 DPI, s evere by 10 DPI, and mostly resolved by 15 DPI. No lesions were observ ed in the intestines of these pigs. There was no clinical respiratory disease. Control pigs remained normal and had no lesions. PRCV was iso lated from the lungs but not from the intestines of inoculated pigs. P RCV was not isolated from the lungs or intestines of control pigs. PRC V was also isolated from the nasal and rectal swabs of inoculated but not of control pigs.