February 11, 2014
According to the Iowa State University Veterinary Diagnostic Laboratory, a second strain of the Porcine Epidemic Diarrhea virus has been detected.
The virus has swept through the US, detected in Iowa in April 2013. And to date have been confirmed in 23 US states and recently two cases have been confirm In Ontario, Canada. The main pork producing state in Canada.
Iowa State University Veterinary Diagnostic Laboratory states that "Based on the data currently available, it appears unlikely that this strain is a mutant evolved from PEDV previously identified in US swine. Determination of the entire genome sequences of these new PEDVs are in progress and will help determine the origin of the viruses."
The report is below:
New PEDV Strains detected in US Swine
Iowa State University Veterinary Diagnostic Laboratory (ISU VDL) is offering PEDV S1 (first 2.2 kb portion
of the spike gene) sequencing to the clientele to help determine the genetic relatedness and molecular
epidemiology of PEDV in US swine. During the time periods of January 24 – January 29, 2014, PEDV S1
sequencing was performed on 15 PEDV cases at ISU VDL. Among them, PEDV S1 sequences from 10 cases
(ISU cases 6-15) are similar to each other and to the PEDV strains identified in US swine since April 2013
(99.1-100% nucleotide identities). In distinct contrast, the PEDV S1 sequences from the other 5 cases (ISU
cases 1-5) only have 93.9-94.6% nucleotide identities to the PEDV strains previously identified in US swine.
However, these 5 PEDV cases shared 99.6-100% nucleotide identities to each other based on the S1 sequences.
Phylogenetic analysis based on the S1 sequences demonstrated that aforementioned 10 PEDV cases clustered
together with PEDV strains identified in US since April 2013. However, the aforementioned 5 PEDV cases
clustered very differently from the PEDV strains previously identified in US swine (Figure 1, Page 2). Sequence
alignment showed that the S1 sequences of these 5 PEDV cases had some deletions and insertions compared to
PEDV viruses previously identified in US.
Based on the data currently available, it appears unlikely that this strain is a mutant evolved from PEDV
previously identified in US swine. Determination of the entire genome sequences of these new PEDVs are in
progress and will help determine the origin of the viruses.
The PEDV real-time RT-PCR offered at ISU VDL is targeting the nucleocapsid (N) gene. The N-gene is known
to be a conserved portion of the PEDV genome. Thus far, the PEDV N-gene real-time RT-PCR being
conducted at the ISU VDL seems to be readily detecting these new PEDVs. The full-length N gene sequences
of the new PEDVs have been determined and were similar to the PEDVs previously identified in the US.
For more information, please contact ISU VDL.