dr. phil gauger - porcine epidemic diarrhea virus in north america
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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
0
2000
4000
6000
8000
10000
ISU-VDL: PEDV Molecular Tests
PEDV PCR
Year/Month
To
tal
PE
DV
Tes
ts
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
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