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

Fecal virus shedding from the inoculated 3-week-old piglets is summarized in Table 5 and Fig 2B. Pigs in all groups were PCR negative on rectal swabs collected before inoculation and at 1 DPI. One pig each in groups 1 and 2 along with two pigs in group 3 were PCR positive on rectal swabs by 2 DPI. All pigs in groups 1-3 were PEDV PCR positive by 4 DPI and remained positive through at least 7 DPI although there were variations on PCR Ct values between individual pigs. Most of the remaining pigs in groups 1-3, after necropsy at 7 DPI, continued to shed virus in rectal swabs during 10-21 DPI but all pigs in these groups ceased shedding virus at 28 DPI (Table 5 ). Based on the quantitative genomic copies/ml of PEDV RNA in rectal swabs, the average virus shedding in groups 1-3 (10 −3 to 10 −5 dilutions) had similar patterns: increasing virus shedding during 2-6 DPI and decreasing virus shedding after 7 DPI (Fig 2B) . However, pigs in group 2 (10 −4 dilution) had a peak virus shedding during 10-14 DPI (Fig 2B) . All rectal swabs from pigs in groups 4-7 (10 −6 to 10 −8 dilutions and negative control) were negative by PEDV PCR through the study period. Cecum contents obtained at necropsy were also tested by PEDV PCR in all pigs and the results were consistent with those of the rectal swabs collected on the corresponding necropsy days (data not shown).