Dr. Albert Rovira - Diagnostic View of Porcine Epidemic Diarrhea Virus

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Diagnostic View of Porcine Epidemic Diarrhea Virus - Dr. Albert Rovira, Assistant Clinical Professor, Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, from the 2013 Allen D. Leman Swine Conference, September 14-17, 2013, St. Paul, Minnesota, USA.

More presentations at http://www.swinecast.com/2013-leman-swine-conference-material

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Dr. Albert Rovira - Diagnostic View of Porcine Epidemic Diarrhea Virus

  1. 1. Porcine Epidemic Diarrhea Virus (PEDV) Albert Rovira, DVM, MS, PhD Veterinary Diagnostic Laboratory
  2. 2. Porcine Epidemic Diarrhea • PED is caused by a coronavirus (PEDV) • PEDV causes diarrhea and vomiting in swine of all ages • High mortality in piglets under 2 weeks of age
  3. 3. Porcine Epidemic Diarrhea • PEDV first described in Europe in the 70s • PED currently not a problem in Europe • PED is an important problem in Asia
  4. 4. Porcine Epidemic Diarrhea • PEDV replicates in the epithelial cells of the small intestine • Incubation period: 1-2 days • Shedding in feces: 7-11 days • Immune response: mucosal and serological: serum antibodies at 7-14 dpi
  5. 5. Source: AASV
  6. 6. Diagnostics • Same basic guidelines of diarrhea diagnostic workups • Select live, acutely affected pigs with diarrhea • Perform necropsy and collect samples within 15 minutes of euthanasia • Gross lesions: liquid intestinal contents, thinwalled intestines?
  7. 7. Sample collection • Small intestine: – 6 sections representing the whole length of the small intestine – 10 cm segments fresh and 2 cm segments fixed • Other tissues for a complete workup and to rule out differential diagnoses – Stomach, colon, tonsil, lymph node, lung, heart, spleen, liver, kidney -- fresh and fixed
  8. 8. Other sample types • Feces • Fecal swabs • Oral fluids • Feedback material • Environmental swabs • Feed
  9. 9. PEDV diagnostic tests • Virus isolation: – Difficult to grow in vitro • Electron Microscopy: – low sensitivity • Histopathology: – atrophic enteritis – same as TGEV and Rotavirus • Real time PCR: – sensitive and specific – available in US laboratories
  10. 10. PEDV diagnostic tests • IHC, ISH: – less sensitive than PCR – good for research, retrospective studies • Serology: – Indicative of previous exposure – IFA/IPMA: will be available first – ELISA: available in Asia, under development in the US
  11. 11. Testing protocols • Diagnostic investigation in farms with diarrhea: – Tissues from acutely affected pigs – Fecal samples: 15 samples in pools of 5 (3 PCRs) – Oral fluid samples from 2 pens • Monitoring the status of farms with no diarrhea: – Fecal samples: 15 samples in pools of 5 – 2 oral fluid samples – 10-15 serum samples for serology
  12. 12. Testing protocols • Monitoring the status of positive sow farms after herd closure – Fecal samples: 30 samples in pools of 5 – Serology on sentinels? • Example: – 8 wks after clinical signs: 10/10 positives – 12 wks after clinical signs: 7/30 positives – 14 wks after clinical signs: 1/30 positives
  13. 13. 35 30 0 15-Mar 17-Mar 19-Mar 21-Mar 23-Mar 25-Mar 27-Mar 29-Mar 31-Mar 2-Apr 4-Apr 6-Apr 8-Apr 10-Apr 12-Apr 14-Apr 16-Apr 18-Apr 20-Apr 22-Apr 24-Apr 26-Apr 28-Apr 30-Apr 2-May 4-May 6-May 8-May 10-May 12-May 14-May 16-May 18-May 20-May 22-May 24-May 26-May 28-May 30-May 1-Jun 3-Jun 5-Jun 7-Jun 9-Jun 11-Jun 13-Jun 15-Jun 17-Jun 19-Jun 21-Jun 23-Jun 25-Jun 27-Jun 29-Jun Number of Cases First cases observed in May Negative POSITIVE 25 20 15 10 5
  14. 14. 500 0 15-Mar 17-Mar 19-Mar 21-Mar 23-Mar 25-Mar 27-Mar 29-Mar 31-Mar 2-Apr 4-Apr 6-Apr 8-Apr 10-Apr 12-Apr 14-Apr 16-Apr 18-Apr 20-Apr 22-Apr 24-Apr 26-Apr 28-Apr 30-Apr 2-May 4-May 6-May 8-May 10-May 12-May 14-May 16-May 18-May 20-May 22-May 24-May 26-May 28-May 30-May 1-Jun 3-Jun 5-Jun 7-Jun 9-Jun 11-Jun 13-Jun 15-Jun 17-Jun 19-Jun 21-Jun 23-Jun 25-Jun 27-Jun 29-Jun Number of Cases >100 positive submissions in 2 months 600 Negative POSITIVE 400 300 200 100
  15. 15. Were we ready for a foreign animal disease outbreak? • VDLs: – Early identification of the disease – PCR test available within days – Real-Time PCR test available within 2 wk (results in 24h) • Immediate involvement of Universities, USDA-APHIS, AASV, NPB
  16. 16. Sharing of lab results to obtain a national monitoring system for PED • U of Minnesota and ISU combined results database maintained at ISU • Combined database transferred to USDA-APHIS– NAHLN • Weekly summary • Collaboration Universities–USDA–AASV-NPB
  17. 17. MN VDL + ISU + SDSU + KSU + OHADDL
  18. 18. Distribution of PED positives Courtesy of Dr. Dane Goede
  19. 19. Limitations of current national monitoring system for PED • Detail of the data: state, farm type, sample type, result • Quality of the data: missing/wrong data • Quality of the data: reported by submission, not by premise • Include premises ID in submission form and give permission to VDLs to share that info with national database
  20. 20. Where did PED come from? • Asia, Europe,…??? • How did it get here? – Pigs – People – Feed – Wildlife,… • U of M, AAVLD and USDA-CEAH: epidemiological study to answer these questions
  21. 21. Sequencing of Spike gene Courtesy of Doug Marthaler
  22. 22. Did it come from feed products? • Some feed ingredients tested positive by PCR • We performed a bioassay to figure out is it was live virus • 3 pigs inoculated with PBS (negative controls) • 3 pigs inoculated with PCR-positive feed products (bioassay) • 3 pigs inoculated with PCR-positive fecal samples (positive controls)
  23. 23. Results bioassay Vomit Diarrhea PED PCR Atrophic enteritis NEG Control No 1/3 0/3 0/3 Bioassay No No 0/3 0/3 YES 2/3 3/3 3/3 POS Control CONCLUSION: feed can contain PEDV nucleic acid that is not infectious but can test positive by PCR

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