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.

b Porcine epidemic diarrhea virus (PEDV) was detected in May 2013 for the first time in U.S. swine and has since caused significant economic loss. Obtaining a U.S. PEDV isolate that can grow efficiently in cell culture is critical for investigating pathogenesis and developing diagnostic assays and for vaccine development. An additional objective was to determine which gene(s) of PEDV is most suitable for studying the genetic relatedness of the virus. Here we describe two PEDV isolates (ISU13-19338E and ISU13-22038) successfully obtained from the small intestines of piglets from sow farms in Indiana and Iowa, respectively. The two isolates have been serially propagated in cell culture for over 30 passages and were characterized for the first 10 passages. Virus production in cell culture was confirmed by PEDV-specific real-time reverse-transcription PCR (RT-PCR), immunofluorescence assays, and electron microscopy. The infectious titers of the viruses during the first 10 passages ranged from 6 ؋ 10 2 to 2 ؋ 10 5 50% tissue culture infective doses (TCID 50 )/ml. In addition, the full-length genome sequences of six viruses (ISU13-19338E homogenate, P3, and P9; ISU13-22038 homogenate, P3, and P9) were determined. Genetically, the two PEDV isolates were relatively stable during the first 10 passages in cell culture. Sequences were also compared to those of 4 additional U.S. PEDV strains and 23 non-U.S. strains. All U.S. PEDV strains were genetically closely related to each other (>99.7% nucleotide identity) and were most genetically similar to Chinese strains reported in 2011 to 2012. Phylogenetic analyses using different genes of PEDV suggested that the full-length spike gene or the S1 portion is appropriate for sequencing to study the genetic relatedness of these viruses.

Porcine deltacoronavirus (PDCoV) was first identified in Hong Kong in 2009-2010 and reported in United States swine for the first time in February 2014. However, diagnostic tools other than polymerase chain reaction for PDCoV detection were lacking and Koch's postulates had not been fulfilled to confirm the pathogenic potential of PDCoV. In the present study, PDCoV peptide-specific rabbit antisera were developed and used in immunofluorescence and immunohistochemistry assays to assist PDCoV diagnostics. The pathogenicity and pathogenesis of PDCoV was investigated following orogastric inoculation of 5-day-old piglets with a plaque-purified PDCoV cell culture isolate (3 × 10(4) TCID50 per pig). The PDCoV-inoculated piglets developed mild to moderate diarrhea, shed increasing amount of virus in rectal swabs from 2 to 7 days post inoculation, and developed macroscopic and microscopic lesions in small intestines with viral antigen confirmed by immunohistochemistry staining. This study experimentally confirmed PDCoV pathogenicity and characterized PDCoV pathogenesis in neonatal piglets.

No abstract