PORCINE EPIDEMIC DIARRHEA VIRUS (PEDV)

BACKGROUND AND CURRENT SITUATION IN THE USA

Tanja Opriessnig

The Roslin Institute, University of Edinburgh, UK

Veterinary Diagnostic and Production Animal Medicine

Iowa State University, USA

PRDC

PEDV Background

• Discovered in 1971 in the UK – Acute outbreaks of diarrhea in feeder pigs and fattening pigs– Suckling pigs did not become sick– Oldham et al., 1972

• Family Coronaviridae– Enveloped, positive stranded RNA viruses– Subfamilies: Coronavirinae & Torovirinae

– Important for pigs:• Genus Alphacoronavirus

– PEDV, TGEV: Diarrhea– PRCV: Respiratory disease

• Genus Betacoronavirus – Porcine haemaggluination encrophalomyelitis virus (HEV): Encephalomyelitis

• Genus Deltacoronavirus– Porcine deltacoronavirus (PDCV): Diarrhea (?)

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PEDV Background

• Structure:– Nucleocapsid (N) protein

• Highly conserved: Best for testing

– Spike (S) protein– Integral membrane (M) protein– Small envelope (E) protein

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3397359

Membrane protein M

Envelope protein E

Spike

Nucleocapsid

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PEDVAge group Diarrhea Mortality

Suckling pigs ++++100% in

naïve populations

Nursery pigs +++ ++

Grow-finish pigs ++ -

Adults + -

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PEDV PEDV Shedding

• Possible contribution factors:– Age dependency– Differences in virulence between isolates?– Cross-protection between strains?– Interaction with other pathogens?

Fecal shedding:• Up to at least 28-

35 + days post infection (neonatal and nursery pigs)

• Large amounts

Viremia:• Short (days)• Low amounts

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PEDV Global Importance

19712013

1993

1982

China:Severe epidemics in recent years

Europe:Epidemics until the late 80ies; Reports after 2000 are rare

• Only infectious for pigs– No role in public health

USA:PEDV still spreading

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PEDV USA Discovery Timeline

MON TUE WED THU FRI SAT SUN

April 15DiarrheaIA

April 16 April 17 April 18 April 19 April 20 April 21

April 22 April 23 April 24 April 25 April 26 April 27 April 28

April 29DiarrheaIA

April 30DiarrheaIA

May 1 May 2 May 3 May 4 May 5

May 6DiarrheaIA

May 7 May 8DiarrheaIN

May 9 May 10EM-CoV

May 11DiarrheaCO

May 12Pan-CoVPCR +

May 13NVSLSequencing

May 14 May 15SequencingPEDV China

May 16NVSL confirms

May 17USDA announces

May 18 May 18

Source: ISU-VDL 2013

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PEDV U.S. Pig Inventory 2007

http://www.factoryfarmmap.org/#animal:hogs;location:US;year:2007

Density Level

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PEDV April 2013

IA

IN OH

Introduction of PEDV into the USA TIMELINE

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PEDV May 2013

IA

INOH

MI

PA

OK

CO

SD

MN

IL

Introduction of PEDV into the USA TIMELINE

MO

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PEDV June 2013

IA

INOH

MI

PA

OK

CO

SD

MN

KS

NY

IL

Introduction of PEDV into the USA TIMELINE

MO

NC

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PEDV July 2013

IA

INOH

MI

PA

OK

CO

SD

MN

KS

NY

TX

TN

WI

IL

Introduction of PEDV into the USA TIMELINE

MO

NC

PRDC

PEDV October 2013

IA

INOH

MI

PA

OK

CO

SD

MN

KS

NY

TX

TN

WI

IL

Introduction of PEDV into the USA TIMELINE

MO

NC

MD

KY

PRDC

PEDV December 2013

IA

INOH

MI

PA

OK

CO

SD

MN

KS

NY

TX

TN

WI

IL

Introduction of PEDV into the USA TIMELINE

MO

NC

MD

KY

NE

WY

CA

PRDC

PEDV January 2014

IA

INOH

MI

PA

OK

CO

SD

MN

KS

NY

TX

TN

WI

IL

Introduction of PEDV into the USA TIMELINE

MO

NC

MD

KY

NE

WY

CA

AZ SC

PRDC

PEDV February 2014

IA

INOH

MI

PA

OK

CO

ND

MN

KS

NY

TX

TN

WI

IL

Introduction of PEDV into the USA TIMELINE

MO

NC

MD

KY

NE

WY

CA

SD

MT

ID

AZSC

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PEDV March 2013

IA

INOH

MI

PA

OK

CO

SD

MN

KS

NY

TX

TN

WI

IL

Introduction of PEDV into the USA TIMELINE

MO

NC

MD

KY

MT

ID

ND

SCAZ

CA

NE

WY

MS

VT

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PEDV Distribution of PEDV in the U.S

Source: AASV

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PEDV

Image Source: ISU-VDL 2013

Total Number of Positive Pig Samples

15-Jun-13 to 8-May-14:

Age group No.

Suckling 1,366/2,343 (49.3%)

Nursery 1,183/2,817 (36.8%)

Grow/finisher 1,199/3,123 (28.3%)

Sows/Boars 558/1,380 (28.6%)

TOTAL 4,306/9,663 (44.6%)

29 (30) States are affected to date

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PEDV

Source: Huang Y et al. mBio 2013; doi 10.1128/mBio.00737-13

2013 Genotyping

Historical PEDVs in Europe and Asia

Emerging PEDVs in Asia and the US

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PEDV Origin of the U.S. PEDV strains

Source: Huang Y et al. mBio 2013; doi 10.1128/mBio.00737-13

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PEDV Evidence of 2nd PEDV Introduction2014

Source: Wang et al. Emerging Infectious Disease 2014; No. 5, May 2014

Whole genome sequencing

Spike protein sequencing

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PEDV Diagnostics

• Diagnostic Specimens– Intestines (Fresh)– Feces– Oral fluids

– Intestines (Fixed)

– Serum

Virus isolationReal-time RT-PCR Electron microscopy

Indirect Fluorescent Antibody, ELISA

Immunohistochemistry

Sequencing

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PEDV

Total Number of Positive Pig Samples

Weekly Basis

Source: AASV

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PEDV Cumulative Number of Positive Samples

6,421

Source: AASV

16-J

un22

-Jun

28-J

un4-

Jul

10-J

ul16

-Jul

22-J

ul28

-Jul

3-A

ug9-

Aug

15-A

ug21

-Aug

27-A

ug2-

Sep

8-S

ep14

-Sep

20-S

ep26

-Sep

2-O

ct8-

Oct

14-O

ct20

-Oct

26-O

ct1-

Nov

7-N

ov13

-Nov

19-N

ov25

-Nov

1-D

ec7-

Dec

13-D

ec19

-Dec

25-D

ec31

-Dec

6-Ja

n12

-Jan

18-J

an24

-Jan

30-J

an5-

Feb

11-F

eb17

-Feb

23-F

eb1-

Mar

7-M

ar13

-Mar

19-M

ar25

-Mar

31-M

ar6-

Apr

12-A

pr18

-Apr

24-A

pr

0

1000

2000

3000

4000

5000

6000

7000

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PEDV PEDV Economic Impact

• Approximately 5 million pigs have died in the U.S.– About 4.5% of the animals sent to processing

plants last year in the U.S– Source: AgriTrends

• It is estimated 12.5 million fewer pigs will be slaughtered in 2014, which will result in an overall U.S. pork production decline of 6-7%– Largest estimated decrease in 30 years– Source: Rabobank

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PEDV Economic Impact of PEDV• Estimated shortfall in market hogs from PEDV to

North American slaughters • ((Source: Rabobank)0%

-5%

-10%

-15%

-20%

-25%

Dec 13 Mar 14 Jun 14 Sep 14 Dec 14 Mar 15 Jun 15 Sep 15 Dec 15

USCanada

Mexico

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PEDV Porcine Deltacoronavirus (PDCV)

• Initially discovered in Hong Kong in 2009 (Woo et al., 2012)

• Described in the U.S. in 2014– Associated with diarrhea in sows and

their litters– No experimental data to date– Precise pathogenesis and role of PDCV

is currently unknown

PDCV

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PEDV Distribution of PDCV in the U.S.

Source: AASV

PDCV

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PEDV PEDV versus PDCV Cumulative US results

PEDV PDCV

Positive Accessions 6,421 142

Total Accessions tested 17,468 1,091

% 36.8% 13.0%

Positive States 29 (30) 14

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PEDV PEDV TransmissionWhat is known so far

• Rapidly spread across U.S.– Transport vehicles

• PEDV negative trucks returning from abattoirs positive (Lowe et al., 2014)

– Animal movement– Aerosol transmission?

Source: Dr. Darin Madson

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PEDVPEDV TransmissionRole of Feed

• Detection of PEDV RNA in feed– Confirmation of PEDV RNA in porcine plasma derived products– Relationship with PEDV outbreaks in Canada?

• Recall of pelleted nursery feeds containing plasma ingredients in Ontario

– CFIA (18-Feb-14); Feedstuffs (20-Feb-14)– 4-Mar-14: CFIA could not confirm live virus in feed pellets

containing blood plasma • Ban of spray-dried porcine plasma products in the UK (Vet

Rec, May 2014)

• Centre de développement due pork du Québec Inc (CDPQ) risk analysis

– Feed is medium risk for PEDV transmission – Study by Scott Dee, Pipestone Applied Research

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PEDV 2014 ISU Experiment

Group Designation

No. of pigs

Diet Inoculation

Dpi 0

NEG-CONTROL 8 No SDPP PBSSDPP-CONTROL 8 5% SDPP PBS

PEDV-CONTROL 8 No SDPP PEDV

Viremia only in PEDV-CONTROL groupSeroconversion only in PEDV-CONTROL group

Conclusion: No evidence of infectivity of the PEDV present in the investigated plasma lot

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PEDV Summary

• PEDV is now prevalent in the majority of swine producing states in the USA

• Epidemic situation Endemic situation?

• Lesion learned: Constant awareness– Globalization increases the risk of pathogen introductions– Need to invest in rapid epidemiological studies to

document how PEDV was introduced to the US and learn from this situation

– Need much more work on advancing understanding of transmission routes

• Pigs, people, trucks, fomites, feed, air, water etc…

STOP PEDV