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.

No abstract

Porcine epidemic diarrhea virus (PEDV) was first recognized in North America in April 2013 and has since caused devastating disease. The objective of this study was to characterize disease and viral detection associated with an original North American PEDV isolate inoculated in neonatal piglets. Thirty-six 1-day-old cesarean-derived and colostrum-deprived piglets were randomly assigned to the control (n ¼ 16) or challenged group (n ¼ 20); the latter were orogastrically inoculated with 1 ml of US/Iowa/ 18984/2013 PEDV isolate titered at 1 Â 10 3 plaque-forming units per milliliter. Rectal swabs were collected from all piglets prior to inoculation and every 12 hours postinoculation (hpi) thereafter, with 4 control and 5 challenged piglets euthanized at 12, 24, 48, and 72 hpi. One piglet had a positive real-time quantitative polymerase chain reaction test on rectal swab at 12 hpi, and all remaining piglets were positive thereafter, with highest viral quantities detected at 24 and 36 hpi. Diarrhea was evident in 30% and 100% of challenged piglets at 18 and 24 hpi, respectively. Viral antigen was detected in enterocytes by immunohistochemistry in the duodenum and ileum of piglets euthanized at 12 hpi and was apparent throughout the small intestine of all piglets thereafter, with villus height:crypt depth ratios consistently below 4:1. Viremia was confirmed in 18 of 20 pigs at euthanasia. Clinical disease was severe and developed rapidly following infection with an original North American PEDV isolate, with lesions, viremia, and antigen detection possible by 12 hpi.

Six porcine epidemic diarrhea viruses (PEDVs) were isolated from the fecal samples of piglets infected with PEDV in 2006 in China. The membrane (M) protein genes of six PEDV isolates were amplified by reverse transcriptase-polymerase chain reaction (RT-PCR), then cloned, sequenced, and compared with each other as well as those ten PEDV reference strains. The M protein genes of six Chinese PEDV isolates consisted of 692 nucleotides containing a single open reading frame (ORF) of 681 nucleotides, which encoded a 226aa-long peptide. The conserved intergenic motif (ATAAAC), as previously recognized in Br1/87, was found in the 5 nucleotides upstream of the initiator ATG of M protein genes of six Chinese PEDV isolates. The hexamer motif was also found in CV777, JMe2, LZC, and QH. The M protein of six isolates had three main transmembrane domains (aa20-38, aa43-65, aa75-97). The M protein of one isolate, CH/IMT/06, had one potential glycosylation site, but those of the other five isolates had two. The glycosylation sequence Asn-Phe-Thr was highly conserved in the M proteins of six PEDV isolates. The six PEDV isolates showed nucleotide sequence homology between 98.8 and 100% and deduced amino acid sequence homology between 98.2 and 100% with each other. The nucleotide and amino acid identity of M protein genes between the six PEDV isolates and ten reference PEDV strains varied from 97.2 to 99.4% and 96.9 to 100%, respectively. On the basis of the phylogenetic relationship of M protein genes, six Chinese PEDV isolates composed of a separate cluster including one Chinese strain JS-2004-02, however, not including the Chinese strain LJB/03. These results demonstrated that there was a new genotype of PEDV prevailing in China.