PEDv Update – November 6, 2013

November 6, 2013 — 

1. The new case report was not received in time to get it posted to the website and listed on the latest AASV e-Letter on Wednesday. We have now posted the results on the website. Last week’s submissions show a continued increase in new accessions and an additional state, Maryland, was also added. This brings the number of states with at least one confirmed case of PEDv to 19.
2. University of Minnesota’s Swine Health Monitoring Project reports the following research results:
   1. Infectious Dose of PEDv -- courtesy of S Goyal & A Rovira, University of Minnesota
      To determine the infectious dose of PEDv, we conducted the following experiment. Serial 10-fold dilutions of PEDv (clarified homogenate of intestinal mucosa from infected piglets) were prepared in PBS and were tested by RT-PCR. This is a continuation of the infectious dose work performed two weeks ago using more dilutions. Ct values of undiluted PEDv and10-1 were 16.39 and 17.73 respectively, but were not used for inoculation in this study. Severity of diarrhea caused by the different virus dilutions was evaluated. Two days after virus inoculation, the pigs were euthanized, their intestinal mucosa collected, and tested for PEDv by PCR. The results indicate that PEDv is highly infectious, the MID50 is very low, and that there may still be enough live virus in a sample that has a PCR-negative result to infect and replicate in a piglet’s intestinal tract. Please note that these results are from a single homogenate of intestinal mucosa from infected piglets and not from cell culture-grown virus.

      [Morrison note – Two points. The results exhibited a negative PCR reaction at 10-8 and yet pigs became infected; a reminder that PCR is not 100% sensitive. And then think about 10-8 dilution still being infectious. That’s equivalent to 1 gram of piglet diarrhea diluted into 100 cubic meters. So about 1 pencil eraser of piglet diarrhea diluted into double my office space filled with saline is still infectious for a 10 day old piglet. That’s a problem.]

   2. Evaluation of Time and Temperature Sufficient to Inactivate PEDv in Swine Feces on Metal Surfaces -- Courtesy of D Holtkamp & R Main, Iowa State University
      These results suggest that it may be possible to inactivate PEDv in the presence of feces by heating trailers to 160oF for 10 minutes or by maintaining them at room temperature for at least 7 days. Other combinations of time and temperature evaluating were not sufficient to kill the virus.

      The investigators do not propose that this is a preferred alternative to thoroughly washing, disinfecting, and drying trailers after hauling PEDv-positive animals. Rather, this work demonstrates the value of possible alternatives when proper washing and disinfection absolutely cannot be accomplished as a means to reduce the risk of transmitting PEDv between groups of animals.

   3. Lagoon Sampling – Dr Bob Morrison (personal communication):
      Initial lagoon sample exhibited a Ct of 22. The same lagoon was re-sampled about 2 weeks later and exhibited a Ct of 25. This is an incredibly high virus concentration in such a large volume. Then this lagoon water is recycled and, during the pit flush process, splashes up onto slats resulting in likely re-contamination of the facilities thus presenting a major challenge to eliminate virus.