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Research Project: INTERVENTION STRATEGIES TO CONTROL VIRAL DISEASES OF SWINE

Location: Virus and Prion Research

Title: Tissue localization, shedding, virus carriage, antibody response, and aerosol transmission of porcine epidemic diarrhea virus (PEDV) following inoculation of 4 week-old feeder pigs

Author
item Niederwerder, Megan - Kansas State University
item Nietfeld, Jerome - Kansas State University
item Bai, Jianfa - Kansas State University
item Peddireddi, Lalitha - Kansas State University
item Breazeale, Barbara - Kansas State University
item Anderson, Joe - Kansas State University
item Kerrigan, Maureen - Kansas State University
item An, Baoyan - Kansas State University
item Oberst, Richard - Kansas State University
item Crawford, Kimberly - Oak Ridge Institute For Science And Education (ORISE)
item Lager, Kelly

Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2016
Publication Date: 11/1/2016
Citation: Niederwerder, M.C., Nietfeld, J.C., Bai, J., Peddireddi, L., Breazeale, B., Anderson, J., Kerrigan, M.A., An, B., Oberst, R.D., Crawford, K., Lager, K.M., Madson, D.M., Rowland, R.R., Anderson, G.A., Hesse, R.A. 2016. Tissue localization, shedding, virus carriage, antibody response, and aerosol transmission of porcine epidemic diarrhea virus following inoculation of 4-week-old feeder pigs. Journal of Veterinary Diagnostic Investigation. 28(6):671-678.

Interpretive Summary: In April of 2013 porcine epidemic diarrhea virus (PEDV) emerged in the US. Although this virus is found in many countries, this was the first detection of PEDV in North America. The virus spread rapidly throughout the swine dense regions of the US and caused severe disease in neonatal pigs resulting in 100% mortality. Older pigs could survive the disease, but had varying levels of reduced growth rates. The purpose of this study was to determine how the virus might affect 4-week-old feeder pigs, transmit among pigs, and how long pigs might shed the virus. Pigs became sick several days after challenge developing a mild-to-moderate diarrhea that lasted for about 5 days at which time they began to recover. By 2 days-post-challenge (dpc) pigs began shedding PEDV in feces which lasted up to 4 weeks in some animals despite appearing normal. All pigs had developed PEDV antibody by 14 dpc and remained antibody positive until 42 dpc, the end of the study. Although disease was relatively mild and transient in this age group, the results demonstrate that 4 week-old pigs are productively infected and can sustain virus replication for several weeks. Long-term shedding of PEDV in subclinical pigs should be considered an important source for PEDV transmission.

Technical Abstract: Porcine epidemic diarrhea virus (PEDV) emerged in the U.S. in April 2013 and caused significant losses to the swine industry. The purpose of this investigation was to determine tissue localization, shedding patterns, virus carriage, antibody response, and aerosol transmission of PEDV following inoculation of 4 week-old feeder pigs. Thirty-three pigs were randomly assigned to one of three groups for the 42 day study; challenge (Group A; n=23), contact transmission (Group B; n=5) and aerosol transmission (Group C; n=5). Contact transmission occurred rapidly to Group B pigs whereas productive aerosol transmission failed to occur to Group C pigs. Emesis was the first clinical sign noted at 3 days post-inoculation (DPI) followed by mild to moderate diarrhea lasting for an additional 5 days. Real-time PCR detected PEDV in fecal and nasal swabs, oral fluids, serum, gastrointestinal and lymphoid tissues. Shedding primarily occurred during the first 2 weeks post-challenge, peaking at between 5 and 6 DPI; however, some pigs had PEDV nucleic acid detected in swabs collected at 21 and 28 DPI. Antibody titers were measurable between 14 and 42 DPI. Although feces and intestines collected at 42 DPI were PEDV negative by PCR and immunohistochemistry, respectively, small intestines from 70% of Group A pigs were PCR positive. Although disease was relatively mild and transient in this age group, the results demonstrate that 4 week-old pigs are productively infected and can sustain virus replication for several weeks. Long-term shedding of PEDV in subclinical pigs should be considered an important source for PEDV transmission.