Pathology of US porcine epidemic diarrhea virus strain PC21A in gnotobiotic pigs

Abstract

To understand the progression of porcine epidemic diarrhea virus infection, we inoculated gnotobiotic pigs with a newly emerged US strain, PC21A, of the virus. At 24–48 hours postinoculation, the pigs exhibited severe diarrhea and vomiting, fecal shedding, viremia, and severe atrophic enteritis. These findings confirm that strain PC21A is highly enteropathogenic.

Figure 1

Electron micrograph of a US porcine epidemic diarrhea virus (PEDV) particle detected in a field fecal sample collected during a 2013 outbreak of PED on a farm in Ohio, USA; the fecal sample from which PEDV strain PC21A in this study was obtained was from a pig on the same farm during the same outbreak. The sample was negatively stained with 3% phosphotungstic acid. Scale bar = 50 nm.

Figure 2

Changes seen, by macroscopic examination, histologic examination, or immunofluorescence staining in the intestine of gnotobiotic pigs inoculated with porcine epidemic diarrhea virus (PEDV; US strain PC21A). A) Intestine of pig 1 at postinoculation hour (PIH) 30 (4–5 h after onset of clinical signs), showing thin and transparent intestinal walls (duodenum to colon) and extended stomach filled with curdled milk. B) Hematoxylin and eosin (H&E)–stained jejunum of pig 3 at PIH 46 (at onset of clinical signs), showing acute diffuse, severe atrophic jejunitis. Original magnification ×200. C) H&E-stained cecum of noninoculated pig 4 (which was exposed to inoculated pig 3 at PIH 0) at 120 h after onset of clinical signs. Acute diffuse, mild vacuolation of superficial epithelial cells (arrows) and subepithelial edema are seen. Original magnification ×200. D) Immunofluorescence staining of jejunum of pig 5 at PIH 67 (37–41 h after onset of clinical signs), indicating that the epithelial cells lining atrophied villi are positive for PEDV. Original magnification ×200. E) Immunofluorescence staining of jejunum of pig 3 at PIH 46 (at onset of clinical signs), showing localization of PEDV antigens in the cytoplasm of enterocytes. Original magnification ×600. F) Immunofluorescence staining of colon of pig 2 at PIH 72 (26–28 h after onset of clinical signs), showing large numbers of PEDV-positive cells. Original magnification ×200. CCL, crypt cell layer. Nuclei were stained with blue-fluorescent 4′, 6-diamidino-2-phenylindole, dihydrochloride.