Emergence of Porcine epidemic diarrhea virus in the United States: clinical signs, lesions, and viral genomic sequences

J Vet Diagn Invest. 2013 Sep;25(5):649-54. doi: 10.1177/1040638713501675. Epub 2013 Aug 20.


During the 10 days commencing April 29, 2013, the Iowa State University Veterinary Diagnostic Laboratory received the first 4 of many submissions from swine farms experiencing explosive epidemics of diarrhea and vomiting affecting all ages, with 90-95% mortality in suckling pigs. Histology revealed severe atrophy of villi in all segments of the small intestines with occasional villus-epithelial syncytial cells, but testing for rotaviruses and Transmissible gastroenteritis virus (Alphacoronavirus 1) were negative. Negative-staining electron microscopy of feces revealed coronavirus-like particles and a pan-coronavirus polymerase chain reaction (PCR) designed to amplify a conserved region of the polymerase gene for all members in the family Coronaviridae produced expected 251-bp amplicons. Subsequent sequencing and analysis revealed 99.6-100% identity among the PCR amplicons from the 4 farms and 97-99% identity to the corresponding portion of the polymerase gene of Porcine epidemic diarrhea virus (PEDV) strains, with the highest identity (99%) to strains from China in 2012. Findings were corroborated at National Veterinary Services Laboratories using 2 nested S-gene and 1 nested N-gene PCR tests where the sequenced amplicons also had the highest identity with 2012 China strains. Whole genome sequence for the virus from 2 farms in 2 different states using next-generation sequencing technique was compared to PEDV sequences available in GenBank. The 2013 U.S. PEDV had 96.6-99.5% identity with all known PEDV strains and the highest identity (>99.0%) to some of the 2011-2012 Chinese strains. The nearly simultaneous outbreaks of disease, and high degree of homology (99.6-100%) between the PEDV strains from the 4 unrelated farms, suggests a common source of virus.

Keywords: Diarrhea; Porcine epidemic diarrhea virus; enteric disease; porcine.

MeSH terms

  • Animals
  • Coronavirus Infections / epidemiology
  • Coronavirus Infections / veterinary*
  • Coronavirus Infections / virology
  • DNA, Viral / chemistry
  • DNA, Viral / genetics
  • Diarrhea / epidemiology
  • Diarrhea / veterinary*
  • Diarrhea / virology
  • Disease Outbreaks / veterinary*
  • Feces
  • Immunohistochemistry / veterinary
  • Microscopy, Electron / veterinary
  • Phylogeny*
  • Porcine epidemic diarrhea virus / genetics
  • Porcine epidemic diarrhea virus / isolation & purification*
  • Porcine epidemic diarrhea virus / ultrastructure
  • Reverse Transcriptase Polymerase Chain Reaction / veterinary
  • Swine
  • Swine Diseases / epidemiology
  • Swine Diseases / virology*
  • United States


  • DNA, Viral