Dr. Phil Gauger - Porcine Epidemic Diarrhea Virus In North America

Porcine Epidemic Diarrhea Virus in North America

Boehringer Ingelheim PEDV Media Conference

World Pork Expo

June 5, 2014

Phil Gauger, DVM, PhDIowa State University/VDPAM/VDL

Molecular Diagnostics Section

PEDV: Background• Porcine Coronaviruses

– Family Alphacoronavirus• Porcine epidemic diarrhea virus: PEDV• Transmissible gastroenteritis virus: TGEV• Porcine respiratory coronavirus: PRCV

– Family Deltacoronavirus• Porcine deltacoronavirus: PDCoV

– PDCV, SDCV

– Diagnostic Tests• Available for the detection of known porcine Coronaviruses• Samples include:

– Feces, fecal swabs, intestine– Oral fluid, environmental samples, other

PEDV vs. PDCoV

• PDCoV is not PEDV or TGEV– Same Family of virus, different Genus

• Delta vs. Alpha• PDCoV is not the variant PEDV

• Field reports: vomiting and diarrhea– Similar clinical signs and lesions to PEDV/TGE– Reportedly more transient &/or less severe – Need isolate and experimental evaluation

• Retrospective testing: ISU-VDL– Earliest date of detection: August 21– Additional testing is in progress

Alphacoronavirus: PEDV

Deltacoronavirus: PDCV

PEDV:Original strainVariant strain

PEDV: Observations• Transboundary introduction

– Non-program disease – Non-reportable disease

• PEDV is not a zoonotic pathogen– No known human food safety risk

• Emerged clinically similar to TGE– Transmissible gastroenteritis

• Diarrhea, vomiting

• ISU-VDL diagnostic testing– Total 57,746 PCR tests

• May 2013 – May 2014– 7,000 samples tested per month

• Molecular diagnostic testing

– Additional testing available

May June July August Sept Oct Nov Dec Jan Feb Mar April2013 2014

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2000

4000

6000

8000

10000

ISU-VDL: PEDV Molecular Tests

PEDV PCR

Year/Month

To

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PE

DV

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PEDV: Emergence in the U.S.• April 28 – May 4 2013

– Four separate ISU-VDL submissions– Similar enteric disease clinical signs

• Diarrhea and vomiting in adult and neonatal swine– >90% neonatal piglet mortality

• Clinically similar to TGE virus– Midwest swine farms

• Iowa (3) and Indiana (1)• No relationship between farms

– Routine diagnostic tests• Suspected enteric pathogens: Negative• Further investigation was necessary

PEDV: Emergence in the U.S.• Collaboration & additional diagnostic testing needed

– ISU-VDL and National Veterinary Services Laboratory– May 6 – May 16, 2013– Virus detection assays in fecal samples

• Pan-coronavirus PCR• Electron microscopy• Genetic sequencing and analysis• Compare sequences in public database

• May 17, 2013– NVSL announces PEDV in the U.S.

PEDV!

PEDV: Current Status• USDA/NAHLN PEDV report

– May 15, 2014: 13 labs voluntarily reporting

• PEDV positive accessions– 6,617– Individual or herd basis

• PEDV positive states– 29 (6,600 swine farms)

• U.S. pork production losses– 7 million pigs since May 2013: 10% of the U.S. pig population– 1.3 million pigs in January 2014

• PEDV detected in Canada and Mexico– Ontario, Manitoba, Quebec and Prince Edward Island

PEDV: Positive States

Source: www.aasv.org

NAHLN Report

Top five states:

Iowa Minnesota

Illinois North Carolina

Oklahoma

PEDV: Clinical Disease• Clinical signs

– Anorexia, lethargy, vomiting– Profuse, watery diarrhea

• All ages affected– Up to 100% mortality in neonatal piglets– Morbidity in nursery, grower, finisher swine– Mild morbidity in adult swine

• Neonatal piglets severely affected– Elongated villi compared to older swine– Mature enterocytes support PED virus replication– Destruction of enterocytes: malabsorption– Neonate intestine fails to recover quickly = mortality

PEDV: Clinical Disease

• Transmission– Fecal-oral– Virus shedding at least 24 days post infection

• Incubation– 12 – 18 hours post-exposure

• Clinical signs– 24 – 72 hours post infection

• Age dependent and variable in older swine• Affected by existing immunity• Virus shedding in large quantities: neonates

24 hours post challenge• Thin-walled intestine

• Watery intestinal content

PEDV: Microscopic Lesions

PEDV affected neonate intestinal villiNormal neonate intestinal villi

PEDV: Diagnostic TestsVirus Detection

• Polymerase Chain Reaction– Detects PEDV genetic material

• Samples: Feces, fecal swabs, oral fluids, environment, feed

• Immunohistochemistry– Detects PEDV antigen

• Associates virus with the lesion

• Genetic Sequencing– Nucleotides of specific genes/whole genome

• Detect differences in viruses

• Virus Isolation– Cell culture Isolate of infectious PEDV

• Poor/variable success: no “bench top” assay for isolating PEDV• Bioassay in swine is an alternative

PEDV: Diagnostic TestsAntibody Detection

• Indirect Fluorescent Antibody– Detects antibody against whole virus antigen

• Serum• Other sample types

– Under investigation

• ELISA Antibody– Detects antibody against whole virus– Detects antibody against specific protein

• Serum• Other sample types

– Under investigation

PEDV: Ecology• Currently two strains of PEDV in the U.S.

– Original strain• Detected April/May 2013• Retrospective testing: April 16, 2013

– Earliest known detection: Ohio• Majority of virus detected are the original strain

– Sequence homology• 99-100% nucleotide identity between original strains

– Mild genetic variation among original PEDV

• Similar to 2012 Chinese PEDV isolate (KC210145)

PEDV whole genome

PEDV: Ecology• Currently two strains of PEDV in the U.S.

– Variant strain• January 2014: ISU-VDL web announcement• February 2014: Ohio State Laboratory• Retrospective testing: detected May 16, 2013

– Earliest known detection: Iowa– IA, IL, IN, MO, KY, MN, NC, NE

– Sequence homology• 99.5-100% nucleotide identity between variant strains• Similar to 2012 Chinese PEDV isolate (JX501318)

These data indicate both PEDV strains have been present in US swine since April/May 2013

• Variants vs Original Strains: – S1 gene sequencing– 93 - 94% nucleotide identity

• U.S. variants: similar changes– Genetic deletion & insertion patterns

• Clinical significance is unknown– Pathogenesis of variant PEDV?– Cross-reactive antibody?– Cross-protection in swine?

• Need a PEDV variant isolate– Cell culture derived virus– Experimental studies

PEDV: EcologyS1 Sequence

PEDV: Challenges• Prevention & control of the virus

– Effective methods of control are inconsistent– Success of controlled exposure is variable

• Vaccination– Few vaccines are currently available– Additional vaccines are needed

• Virus transmission– PEDV continues to infect/re-infect swine populations– Effective biosecurity to prevent transmission

• Diagnostic tests– Measure protective immune response– Duration of immunity in exposed or immunized swine

• Unknowns: Questions remain– How did PEDV enter the U.S.?– Pathogenic differences between original & variant PEDV?– Biosecurity needs and methods of control of PEDV?

• Industry needs: PEDV prevention and control– Additional efficacious vaccines– Additional serological/diagnostic tests– Cell culture isolates of original and variant PEDV– Identify correlates of immune protection– Experimental studies: Pathogenesis and immunology

PEDV: Future Perspectives

PEDV: What Next?• Expand PEDV research and knowledge!

Collaborative efforts are necessary:• Swine industry/producers• Veterinarians• Veterinary diagnostic laboratories• Swine commodity groups• Animal health industry• Animal feed industry• Government regulatory entities

PEDV: Resources• AASV PEDV webpage

• http://www.aasv.org/aasv%20website/Resources/Diseases/PorcineEpidemicDiarrhea.php

• University websites• http://www.cvm.umn.edu/sdec/SwineDiseases/PEDV/index.htm• http://vetmed.iastate.edu/vdpam/disease-topics/porcine-epidemic-diarrhea-ped-diagnostic-testing• http://www.vet.k-state.edu/depts/dmp/service/news/KSVDL_PEDV_fact_sheet.pdf• http://www.aasv.org/documents/SDSUPEDSubmissionGuidelines.pdf

• Other• http://www.ipic.iastate.edu/information/PEDVfactsheet2013.pdf• http://www.pork.org/Home.aspx

Acknowledgements

• USDA/NVSL• Veterinary Diagnostic Laboratories

• American Association of Swine Veterinarians• National Pork Board

• State Pork Associations• U.S. Swine Producers