Porcine Epidemic Diarrhea Virus Update - Dr. Darin Madson, Iowa State University, Veterinary Diagnostic Lab, from the 2013 Boehringer Ingelheim Swine Health Seminar, August 16-18, 2013, Wrightsville Beach, NC, USA.
More presentations at http://www.swinecast.com/2013-boehringer-ingelheim-carolina-swine-health-seminar
2. Veterinary Diagnostic Laboratory
Iowa State University
Porcine Epidemic Diarrhea Virus
• Coronavirus
– TGE-like outbreaks England 1971
• Multiple European Countries
» Most often in nursery/grow finish pigs
• More recently an issue in Asia
» China
» Japan
» Korea
– Severe epizootic outbreaks
Other swine coronaviruses
1. TGE
2. PRCV
3. HEV
3. Veterinary Diagnostic Laboratory
Iowa State University
Porcine Epidemic Diarrhea Virus
• Difficult to propagate in cell culture
• Vero cells with trypsin
– African green monkey kidney cells
• Only one serotype known
– European isolates similar to Asian isolates
• US isolate(s)
• 99.8% similar to 2012 china isolate in genbank
4. Veterinary Diagnostic Laboratory
Iowa State University
Porcine Epidemic Diarrhea Virus
• Enveloped, single-stranded RNA virus
• 7 open reading frames encode 4
structural proteins
– Spike protein (S gene)
– Membrane (M)
– Envelope (E)
– Nucleoprotein (N gene)
• Highly conserved; best for testing Dr. E. Burrough
6. Veterinary Diagnostic Laboratory
Iowa State University
Porcine Epidemic Diarrhea Virus
• Transmission
– Only infectious to swine
– Not humans or other species
– Fecal-oral transmission
• Outbreaks with 4-5 days after pig movements
• Pig-to-pig transmission
– Shedding for 7-9 days
– No long term virus carriers have been reported to date
• Biosecurity
– Trucks, boots, fomites, etc.
– Similar to TGE
7. Veterinary Diagnostic Laboratory
Iowa State University
Porcine Epidemic Diarrhea Virus
• Outcomes of infection
– Endemic
• Lactogenic immunity is protective to piglets
– Eliminated
8. Veterinary Diagnostic Laboratory
Iowa State University
Porcine Epidemic Diarrhea Virus
• Pathogenesis
– Viral attack of mature villous enterocytes
• Diffusely through the small intestine
• Cytoplasmic replication
• Incubation time = 12-18 hrs
• Severe diarrhea at 24-36 hrs (maximum effect)
– Post infection
• Rare detection in colonocytes
– No destruction though
15. Veterinary Diagnostic Laboratory
Iowa State University
Porcine Epidemic Diarrhea Virus
• PEDV has not been detected outside the
intestinal tract
• Previous reports, anyway
• Lung and mesenteric lymph node?
• PEDV is supposedly less severe than TGE
• ISU cases support similar severity to TGE
16. Veterinary Diagnostic Laboratory
Iowa State University
Porcine Epidemic Diarrhea Virus
• Clinical disease
– Watery diarrhea
• Smells like TGE (literally if you can smell TGE)
• Suckling pigs most severely affected
• ~100% morbidity in acute cases
• ~50% mortality from dehydration
– Vomiting (possible)
18. Veterinary Diagnostic Laboratory
Iowa State University
Porcine Epidemic Diarrhea Virus
• Properties
– Stable between a pH of 5-9
– Heat inactivated at 60°C of 30 mins
– Moderately stable at 50°C
20. Veterinary Diagnostic Laboratory
Iowa State University
Porcine Epidemic Diarrhea Virus
• The story………………..
Case Date Location Farm type
1 04/29/13 Iowa Sow
2 05/01/13 Iowa Sow
3 05/06/13 Iowa Nursery
4 05/06/13 Iowa Nursery
5 05/07/13 Indiana Sow
6 05/08/13 Indiana Sow
21. Veterinary Diagnostic Laboratory
Iowa State University
Porcine Epidemic Diarrhea Virus
• All cases had severe diarrhea
– Some vomiting
• All TGE negative
– Samples sent to SDSU and Minnesota as well
• Severe atrophic enteritis
• Sent feces to NVSL for Election
microscopy (EM)
– Positive for coronavirus-like particle (5-10-13)
22. Veterinary Diagnostic Laboratory
Iowa State University
Porcine Epidemic Diarrhea Virus
• NVSL PCR testing for PEDV
– Positive on 5-11-2013
• Announcement
– 5-17-2013
• My life changed 5-17-2003
25. Veterinary Diagnostic Laboratory
Iowa State University
Available PEDv Diagnostics
• PCR
• Multiple PCR tested
• S gene, N gene, and nested
• Currently running
– N gene real-time
– S gene gel based is the back up
– Nested is the third confirmatory test
• PCR samples
– Feces, intestine, oral fluids, feed, Swiffer
Retrospective testing – 800+ samples
26. Veterinary Diagnostic Laboratory
Iowa State University
Available PEDv Diagnostics
• Immunohistochemistry
– Fixed samples
• Not as sensitive as PCR
• Serology
– IFA (very soon)
• Dr. Yoon’s Lab has been able to culture the virus
– ELISA not yet
IHC development 5-25-2013
No retrospective testing to date
27. Veterinary Diagnostic Laboratory
Iowa State University
PEDv Research and Hearsay
• Feed; potential infection source??????
– Numerous samples tested
• Whole feed, premixes, plasma sources, etc.
• 2 samples positive on multiple PCRs
– Vitamin premix
– Plasma product
• Infectivity unknown
– Swine bioassays needed
28. Veterinary Diagnostic Laboratory
Iowa State University
PEDv Research
• Pathogenesis studies underway
– Weaned pig study
– Neonatal pig study
• Evaluating
• Shedding
• Oral fluid detected
• Microscopic lesions
• Clinical signs
29. Veterinary Diagnostic Laboratory
Iowa State University
PEDv Research
Weaned Pig Study
• Diarrhea 2-3 days post
inoculation
• Little vomiting @ 3-4 days
• Extensive diarrhea @ 4-6
days post inoculation
• Recovery @ 8 days; no
depression with scant
diarrhea
• No weight gain for 7 days
• PCR testing N/A yet
Neonatal pig study
• Diarrhea at 24 hours post
inoculation
• Severe diarrhea at 36
hours; all pigs
• Severe emaciation and
dehydration @ 48 hours
• Mortality 36-72 hours
Preliminary data
31. Veterinary Diagnostic Laboratory
Iowa State University
PORCINE EPIDEMIC
DIARRHEA VIRUS
What is next?????
Questions???
Acknowledgments
Dr. Drew Magstadt
Dr. Paulo Arruda
Dr. Yoon
Dr. Stevenson