|GERBER, PRISCILLA - Roslin Institute|
|XIAO, CHAO-TING - Iowa State University|
|CRAWFORD, KIMBERLY - Orise Fellow|
|KULSHRESHTHA, VIKAS - Orise Fellow|
|CAO, DIANJUN - Virginia Polytechnic Institution & State University|
|MENG, XIANG-JIN - Virginia Polytechnic Institution & State University|
|OPRIESSNIG, TANJA - Roslin Institute|
Submitted to: Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2016
Publication Date: 11/21/2016
Citation: Gerber, P.F., Xiao, C.T., Lager, K., Crawford, K., Kulshreshtha, V., Cao, D., Meng, X.J., Opriessnig, T. 2016. 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. Veterinary Research. 47(1):118.
Interpretive Summary: Porcine epidemic diarrhea virus (PEDV) causes diarrhea in swine and is known to spread rapidly after entering naïve pig populations. The disease is recognized as a spectrum with the most severe disease in baby piglets which can result in 100% mortality. As pigs get older, they can still be infected and have diarrhea, but are more resistant to the disease and usually survive. Mature swine may have only transitory signs of disease. Understanding the timing of when pigs can develop a protective immune response will help design PEDV control strategies on the farm. The objectives of this study were to 1) compare the disease course following inoculation with PEDV challenge isolate US/Colorado/2013 in naïve 10-day and 8-week-old pigs, and 2) contrast the response to live virus challenge in naïve 8-week-old pigs with pigs that were previously infected at 10 days of age. When comparing younger pigs to older pigs, the younger pigs had more clinical signs of diarrhea and shed virus in their feces more frequently and for a longer duration. In the pigs that received virus challenge at 10 days of age, and the second challenge at 8 weeks of age, over 90% had complete protection indicating the young pigs had developed good immunity within 46 days of their first exposure. This study complements previous research that demonstrated young pigs could develop protective immunity within 77 days of challenge. Collectively, this work indicates the potential to develop protective immunity in naive young pigs against clinical disease in the nursery. However, additional studies will be necessary to develop safe and efficacious vaccines as opposed to the use of live field virus.
Technical Abstract: Porcine epidemic diarrhea virus (PEDV) causes enteric disease in pigs and is known to spread 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, subsets of 3-10 pigs were euthanized at 1, 2, 3, 7 or 14 days-post-inoculation (dpi). Clinical signs were more pronounced in 10-day-old pigs compared to 8-week-old pigs and at 2 and 3 dpi, a higher number of 10-day-old pigs shed PEDV RNA in feces compared to 8-week-old pigs. Severe atrophic enteritis typical of PEDV infection was observed at 3 dpi in both age groups, and at 4 and 14 dpi fecal shedding patterns were also similar. While both age groups had seroconverted to PEDV by 14 dpi, IgG levels were higher in 8-week-old pigs. 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 protection against homologous challenge 44 days after initial PEDV exposure.