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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ISU-VDL: PEDV Molecular Tests

PEDV PCR

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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