Dr. Darin Madson - Porcine Epidemic Diarrhea Virus Update

Veterinary Diagnostic Laboratory
Iowa State University
Porcine Epidemic Diarrhea Virus Update
Darin Madson
ISU-VDL
madson@iastate.edu

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

• 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

• 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

• 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

• Outcomes of infection
– Endemic
• Lactogenic immunity is protective to piglets
– Eliminated

• 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

Villous to crypt ratio 7:1

Villous to crypt ratio 3:1

• 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

• 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)

• Properties
– Stable between a pH of 5-9
– Heat inactivated at 60°C of 30 mins
– Moderately stable at 50°C

Pospischil et al 2002

• 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

• 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)

• NVSL PCR testing for PEDV
– Positive on 5-11-2013
• Announcement
– 5-17-2013
• My life changed 5-17-2003 

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

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

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

PEDv Research
• Pathogenesis studies  underway
– Weaned pig study
– Neonatal pig study
• Evaluating
• Shedding
• Oral fluid detected
• Microscopic lesions
• Clinical signs

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

PEDv Research
Weaned pigs DPI 3

PORCINE EPIDEMIC
DIARRHEA VIRUS
What is next?????
Questions???
Acknowledgments
Dr. Drew Magstadt
Dr. Paulo Arruda
Dr. Yoon
Dr. Stevenson

Dr. Darin Madson - Porcine Epidemic Diarrhea Virus Update

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Dr. Darin Madson - Porcine Epidemic Diarrhea Virus Update