dr. bob morrison - porcine epidemic diarrhea virus (pedv) transmission
DESCRIPTION
Porcine Epidemic Diarrhea Virus (PEDv) Transmission - Dr. Bob Morrison, University of Minnesota, from the 2014 Boehringer Ingelheim North Carolina Swine Health Seminar, August 15, 2014, Wrightsville Beach, North Carolina, USA. More presentations at http://www.swinecast.com/2014-boehringer-ingelheim-carolina-swine-health-seminarTRANSCRIPT
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Discussion on PED virus
Bob Morrison, Dane Goede, Mike Murtaugh, Albert Rovira, Kurt
Rossow, Sagar Goyal
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Projects
• Recent– Lateral spread
• Current– Swine Health Monitoring Project– National incidence– Production impact– Time to stability– Other current & proposed projects
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PEDv Transmission Risks• U of MN Lateral Spread Study
– Oklahoma panhandle sites– Southeast US sites
• Known samples tested – Birds/pests– Feed– Feces/Lagoons– Transportation– Air
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Lateral Spread Investigative team
• U of Minnesota:– Dane Goede, Peter Davies, Andres Perez, Bob Morrison
• USDA epidemiologists:– Andrea Beam, Charles Haley, Brian McCluskey, Bruce Wagner
• NPB & AASV– Paul Sundberg & Harry Snelson
• Participants:– OK cluster– Southeast
• Whole state• Case / control
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Objective
• To determine if “my” farm is at increased risk of PED virus infection if my neighbor’s farm is infected.
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OK cluster• Data collected from all sites
– Farm ID– Company– Location (geocoordinates)– Capacity– Cause of infection (lateral vs pig movement)
• Spatial Analysis on entire cohort performed– 90 positive sites out of 222 total
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PEDv Risks - Airborne
• Infectious PEDv collected from in-barn air
• 11/64 air samples outside barns (60 ft-10 mi)– None were infectious– Since then, we have isolated infectious virus in air;
Alonso et al 2014.
• Oklahoma panhandle direction of spread similar to prevailing winds
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NC - farm characteristics and spatial features as risk factors for PEDv infection
• 2,071 sites were followed from 7/1/2013 – 1/27/2014 for PEDv occurrence.
• Available data:– Company, production type, total capacity,
geographic coordinates and PEDv status
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• 327 / 2,071 (15.8%) farms became infected with PEDv by unknown mechanisms (lateral)
• 286 / 2,071 (13.8%) became infected by vertical movement.
• Of the 327 laterally infected (cases) sites:– Median capacity 3,600 head– Median distance to nearest +’ve 1.4 miles
PEDv status Production type Negative Positive-
VerticalPositive- Lateral
Total
Sows only 139 2 78 219Sows and growing pigs 71 5 42 118Boar stud 18 0 1 19Growing pigs only 1,230 279 206 1,715Total 1,458 286 327 2,071
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Conclusions• Density
– Risk of infection increases with density.– Distance to neighbor is diluted at high density.
• Rendering service– OR 1.19 / visit or 7.1x in last 2 weeks
• Birds, rodents & feral animals– OR 6-10 x in last 2 weeks
• Not significant– Recent manure application
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SPECIFIC RISK FACTORS
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Infectious Dose of PEDvVirus dilution Initial Ct value of the
virus dilutionExtent of diarrhea Ct value from
inoculated piglets
10-6 33.65 + 15.52
10-7 37.83 ++ 15.52
10-8 - + 16.03
10-9 - - 30.29
10-10 - - -
10-11 - - -
10-12 - - -
• Undiluted PEDv - 16.39 Ct.• PEDv is highly infectious.• Probably age dependent.• May be strain dependent.
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PEDv risks - Birds
• Southeast US risk factor analysis (OR 6-10)• Samples (24 results volunteered)
– Buzzards & geese
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PEDv risks - Feed
• Survival at room temp: 1-2 weeks (Goyal et al 2013)
• Field samples:– Bio-assay of PCR positive feed
• 4/4 were not infectious (Negative bio-assay)
• Herd infection from contaminated feed was reported and reproduced experimentally (Dee et al 2014; also plasma reported in Canada)
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PEDv risks - Feces• Lagoon slurry PEDv survival
– Cold (-20C, 4C) – over 1 month– Room Temp – 14-28 days– 1/4 lagoons still infectious >5 weeks after
shedding stopped
• Fresh feces PEDv survival (Thomas, 2014)– Room temp – 1-7 days– Hot (71C or 165F) – <10 min
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PEDv risks - Transportation• Southeast US risk factor analysis
– Renderer visits to sites (OR 7.1)
• Harvest plant transportation study (Lowe et al, 2013)– Each contaminated truck @ entry 0.96 new
trucks being contaminated
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PEDv risks – Farms• Southeast US risk factor analysis
– High capacity herds (> 2,000 head) had 2.5x higher odds
– Sites w/ sows had 8.8x higher odds than sites w/ growing pigs only
– Sites w/ sows & growing pigs had 5.8x higher odds than sites with growing pigs only
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PEDv risks – Region/Neighbors
• Southeast US risk factor analysis– Increased regional density (>5 sites/25 mi2)
– Distance to nearest neighbor• 10-19% increased odds of being positive each mile
closer• Not as important in high density area (>11 sites/25 mi2)
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Swine Health Monitoring Report ([email protected])
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Swine Health Monitoring Project ([email protected])
• Participants - 17 share logo
• 171 receive weekly report
• Proposed direction
PRRS PED
Participants 14 19
Farms 372 739
Sows 1.2 m 2.1 m
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Present Day
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National Incidence
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National Incidence – NAHLN data
July 9, 2013
Dec 6, ‘13
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National Incidence
Dec 13, ‘13
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National Incidence - regions
January 24, ‘14
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National Incidence – PED year
June 27, ‘14
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EWMA – statistical analysis of incidence
372 herds with 1.2 m sows
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EWMA math
• The smoothed trend line– Lambda = 0.28 for this week and (1-0.28) for last week.
• Control limits– 2.2 * SD of cases / week for June - August– The choice of this number is rather empirical, trying to
minimize false alarms, but not delay signal of a new epidemic.
– CDC uses 1.645 for human influenza epidemic confidence interval
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EWMA – smoothed presentation of trend
Jan 3, ‘14
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EWMA – Re-defined denominator
June 6. ‘14
May 30, ‘14
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EWMA – year end
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National Incidence – 2014/15;EWMA has re-set control limit
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National Incidence
• Incidence & status changes– 1 – Positive– 2v – Stable, on going exposure– 2 – Stable– 3 – Provisionally Negative– 4 - Negative
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Prevalence in 739 herds
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Production impact
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Time to baseline production (TTBP):EWMA chart, back to “in control” level
TTBP(24 weeks)
Montgomery DC. Introduction to statistical quality control. 2012. 7th ed. John Wiley & Sons, Inc.
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Quantifying the production losses:AUC to sum “pigs not weaned”
TTBP(24 weeks)
3,754.8 pigsBelow expected 15,229 pigs
Below expected
“Δ pigs A”“Δ pigs B”
TTBP
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Production Impact: Aggregate
Rapid Response
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Prototype vs. INDEL PEDv
Prototype PEDv (124 herds)
Avg TTBP (3 SD) = 72% @ 12.6 wks Net loss 2.6 pigs/sowAvg TTBP (100%) = 38% @ 15.4 wks Net loss 4.7 pigs/sow
INDEL Variant PEDv (3 herds)
Avg TTBP (3 SD) = 100% @ 4.3 wks Net loss 0.4 pigs/sowAvg TTBP (100%) = 100% @ 6 wks Net loss 0.9 pigs/sow
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4 more Indel herds24 31 7 14 21 28 5 12 19 26 2 9 16 23 30 6 13 20 27 4 11 18 25 1 8 15 22 29 6 13 20 27 3 10 17 24 31 7 14 21 28 7 14 21 28 4 11 18 25 2 9 16 23 30 6 13 20 27 4 11 18 25 1 8 15 22 29 5 12 19 26 3 10 17 24 31 7 14 21 28 5 12 19 26
5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 122013 2014
0
1000
2000
3000
4000
5000
6000
11/29/2013 1/31/2014 63
11/29/2013 1/31/2014 63
11/22/2013 1/17/2014 56
11/15/2013 1/17/2014 63
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Reproductive, endemic infection, re-infection, virulence??
PWM?
Repro?
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Time to Stability
• 26 sites so far enrolled
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Time to StabilityWeeks Post-Exposure
Wee
k 4
Wee
k 5
Wee
k 6
Wee
k 7
Wee
k 8
Wee
k 9
Wee
k 10
Wee
k 11
Wee
k 12
Wee
k 13
Wee
k 14
Wee
k 15
Wee
k 16
Wee
k 17
Wee
k 18
Wee
k 19
Wee
k 20
Wee
k 21
Wee
k 22
Wee
k 23
Wee
k 24
Wee
k 25
Wee
k 26
Wee
k 27
Site 1Site 2Site 3Site 4 Site 5Site 6Site 7Site 8Site 9Site 10Site 11Site 12Site 13Site 14Site 15Site 16Site 17Site 18Site 19Site 20Site 21Site 22
Tested: Positive Tested: Neg (too few litters) Tested: Negative Stable
12 / 26 sites (4 not shown) reached stability so far
Average TTS in those 12 sites is 16.7 weeks(13.8-19.5 )
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Risk factors for prolonged TTS
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Other current & proposed projects• Sow challenge
– Does previous infection with Indel strain confer protection to challenge with prototype strain?
– Collaborative effort with Goede, Dvorak, Murtaugh, Nerem, Yeske, Rossow, Morrison.
• Impact of PEDv in growing pigs• Duration of immunity in gilts?• Effectiveness of vaccination?• Evaluation of immunity within endemic herds?
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Acknowledgements• Study participants• USDA APHIS CEAH – Lateral spread data analysis• SHMP
– Companies sharing logos & other participants– NPPC, AASV, USDA, NPB
• U of MN Veterinary Diagnostic Laboratory• Funding
– National Pork Board & UMN SDEC
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Emerging Infectious Diseases
• Volume 20, Number 10—October 2014• Research• Distinct Characteristics and Complex Evolution of PEDV Strains,
North America, May 2013–February 2014• Anastasia N. Vlasova1, Douglas Marthaler1 , Qiuhong Wang,
Marie R. Culhane, Kurt D. Rossow, Albert Rovira, James Collins, and Linda J. Saif
• Author affiliations: The Ohio State University, Wooster, Ohio, USA (A.N. Vlasova, Q. Wang, L.J. Saif); University of Minnesota Veterinary Diagnostic Laboratory, St. Paul, Minnesota, USA (D. Marthaler, M.R. Culhane, K.D. Rossow, A. Rovira, J. Collins)
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Figure 1. Phylogenetic tree based on complete genome sequences of 112 North American porcine epidemic diarrhea virus strains. Blue font represents US non–S INDEL strains; red font represents US S INDEL strains;
brown font represents Mexican strains; purple font represents worldwide non–S INDEL strains; and pink font represents global S INDEL strains. Bootstrap values are represented at key nodes. Scale bar indicates nucleotide substitutions per site. CH, China; IA, Iowa; S INDEL, insertions and deletions in the spike gene; IN, Indiana; ISU,
Iowa State University; MEX, Mexico; MN, Minnesota; USA, United States of America.