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
Discussion on PED virus
Bob Morrison, Dane Goede, Mike Murtaugh, Albert Rovira, Kurt
Rossow, Sagar Goyal
Projects
• Recent– Lateral spread
• Current– Swine Health Monitoring Project– National incidence– Production impact– Time to stability– Other current & proposed projects
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
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
Objective
• To determine if “my” farm is at increased risk of PED virus infection if my neighbor’s farm is infected.
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
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
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
• 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
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
SPECIFIC RISK FACTORS
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.
PEDv risks - Birds
• Southeast US risk factor analysis (OR 6-10)• Samples (24 results volunteered)
– Buzzards & geese
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)
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
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
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
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)
Swine Health Monitoring Report ([email protected])
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
Present Day
National Incidence
National Incidence – NAHLN data
July 9, 2013
Dec 6, ‘13
National Incidence
Dec 13, ‘13
National Incidence - regions
January 24, ‘14
National Incidence – PED year
June 27, ‘14
EWMA – statistical analysis of incidence
372 herds with 1.2 m sows
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
EWMA – smoothed presentation of trend
Jan 3, ‘14
EWMA – Re-defined denominator
June 6. ‘14
May 30, ‘14
EWMA – year end
National Incidence – 2014/15;EWMA has re-set control limit
National Incidence
• Incidence & status changes– 1 – Positive– 2v – Stable, on going exposure– 2 – Stable– 3 – Provisionally Negative– 4 - Negative
Prevalence in 739 herds
Production impact
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.
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
Production Impact: Aggregate
Rapid Response
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
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
Reproductive, endemic infection, re-infection, virulence??
PWM?
Repro?
Time to Stability
• 26 sites so far enrolled
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 )
Risk factors for prolonged TTS
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?
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
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)
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.