Effect of Porcine Epidemic Diarrhea Virus Infectious Doses on Infection Outcomes in Naïve Conventional Neonatal and Weaned Pigs

Thomas, Joseph T.; Chen, Qi; Gauger, Phillip C.; Giménez-Lirola, Luis G.; Sinha, Avanti; Harmon, Karen M.; Madson, Darin M.; Burrough, Eric R.; Magstadt, Drew R.; Salzbrenner, Holly M.; Welch, Michael W.; Yoon, Kyoung-Jin; Zimmerman, Jeffrey J.; Zhang, Jianqiang

Thin-walled small intestine and soft to watery contents in small intestines, ceca and colons were observed at necropsy in pigs in groups 1-5 (10 −3 -10 −7 dilutions) and one pig (ID 9) of group 6; similar villous atrophy consistent with viral infection was observed in these pigs. Villus height and crypt depth were measured, villus-height-to-crypt-depth ratios were calculated, and the magnitude of IHC staining was scored and compared on ileums of different groups (Table 4 ). Pigs in groups 1-5 (10 −3 -10 −7 dilutions) were all necropsied at 4 DPI and there were no significant differences between groups in villus height, crypt depth, villus/crypt ratio, or IHC scores. Only one pig (ID 9) from group 6 was necropsied at 4 DPI and was thus not included in the statistical analysis. Microscopic intestinal lesions consistent with viral enteritis were not observed in the 3 remaining pigs in group 6 and the negative control pigs (group 7); villus height, crypt depth, and villus/crypt ratio of ileums of these pigs were not significantly different from each other; IHC staining was negative on these pigs. Compared to the pigs in group 6 (IDs 23, 13 and 8) and group 7 (negative control), the pigs in groups 1-5 had decreased villus heights, increased crypt depth, and lower villus/crypt ratios; however, statistical differences were not analyzed because they were necropsied at different DPI.