Increased frequency of porcine epidemic diarrhea virus shedding and lesions in suckling pigs compared to nursery pigs and protective immunity in nursery pigs after homologous re-challenge

Porcine epidemic diarrhea virus (PEDV) causes enteric disease in pigs and spreads rapidly after entering naïve pig populations. The objectives were to (1) compare the disease course following inoculation with PEDV isolate US/Colorado/2013 in naïve 10 day and 8 week-old pigs, and (2) contrast the naïve response to homologous challenge in 8 week-old pigs. Pigs were randomly assigned into group 1 (n = 40, no PEDV exposure), group 2 (n = 43, PEDV inoculation at 10 days of age) and group 3 (n = 48, PEDV inoculation at 8 weeks of age). Thirty-three group 2 pigs received a homologous challenge at 8 weeks of age. Following primary or secondary inoculation, 3-10 pigs were euthanized at days post-inoculation (dpi) 1, 2, 3, 7 or 14. Clinical signs were more pronounced in 10 day-old pigs compared to 8 week-old pigs at dpi 2 and 3, a higher number of 10 day-old pigs shed PEDV RNA in feces compared to 8 week-old pigs. Typical severe atrophic enteritis of PEDV infection was observed at dpi 3 in both age groups, and at dpi 4 and 14 fecal shedding patterns were also similar. While both age groups had seroconverted to PEDV by dpi 14, IgG levels were higher in 8 week-old pigs. PEDV IgA antibodies were detected in feces of approximately 50% of the pigs at dpi 44. In homologous challenged pigs, no clinical signs or lesions were found, and PEDV fecal shedding was restricted to less than 10% of the pigs indicating the existence of homologous protection 44 days after initial PEDV exposure.