1) The document discusses recent and current projects related to PED virus, including a lateral spread study looking at transmission risks through various routes. 2) Risk factors for PED virus infection and transmission are examined, drawing on data from Oklahoma, North Carolina, and the Southeast US. Higher risks are associated with density, proximity to infected farms, and presence of sows. 3) Production impacts of PED virus are quantified through metrics like time to baseline production and aggregate losses across infected farms. Newer INDEL strains may cause less severe outcomes than prototype strains.

1. Discussion on PED virus
Bob Morrison, Dane Goede, Mike
Murtaugh, Albert Rovira, Kurt
Rossow, Sagar Goyal

2. Projects
• Recent
– Lateral spread
• Current
– Swine Health Monitoring Project
– National incidence
– Production impact
– Time to stability
– Other current & proposed projects

3. 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

4. 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

5. Objective
• To determine if “my” farm is at increased risk
of PED virus infection if my neighbor’s farm is
infected.

6. 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

7. 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

8. 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

9. • 327 / 2,071 (15.8%) farms became infected with
PEDv by unknown mechanisms (lateral)
• 286 / 2,071 (13.8%) became infected by vertical
movement.
PEDv status
Production type Negative Positive-
Vertical
Positive-
Lateral
Total
Sows only 139 2 78 219
Sows and growing pigs 71 5 42 118
Boar stud 18 0 1 19
Growing pigs only 1,230 279 206 1,715
Total 1,458 286 327 2,071
• Of the 327 laterally infected (cases) sites:
– Median capacity 3,600 head
– Median distance to nearest +’ve 1.4 miles

10. 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

11. SPECIFIC RISK FACTORS

12. Infectious Dose of PEDv
Virus dilution Initial Ct value of the
virus dilution
Extent 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.

13. PEDv risks - Birds
• Southeast US risk factor analysis (OR 6-10)
• Samples (24 results volunteered)
– Buzzards & geese

14. 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)

15. 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

16. 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

17. 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

18. 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)

19. Swine Health Monitoring Report
(SHMP@UMN.Edu)

20. Swine Health Monitoring Project
(SHMP@UMN.Edu)
• Participants - 17 share logo
PRRS PED
Participants 14 19
Farms 372 739
Sows 1.2 m 2.1 m
• 171 receive weekly report
• Proposed direction

22. Present Day

23. National Incidence

24. National Incidence – NAHLN data
July 9, 2013
Dec 6, ‘13

26. National Incidence
Dec 13, ‘13

27. National Incidence - regions
January 24, ‘14

28. National Incidence – PED year
June 27, ‘14

29. EWMA – statistical analysis of incidence
372 herds with
1.2 m sows

30. 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

31. EWMA – smoothed presentation of trend
Jan 3, ‘14

32. EWMA – Re-defined denominator
May 30, ‘14
June 6. ‘14

33. EWMA – year end

34. National Incidence – 2014/15;
EWMA has re-set control limit

35. National Incidence
• Incidence & status changes
– 1 – Positive
– 2v – Stable, on going exposure
– 2 – Stable
– 3 – Provisionally Negative
– 4 - Negative

36. Prevalence in 739 herds

37. Production impact

39. 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.

40. Quantifying the production losses:
AUC to sum “pigs not weaned”
TTBP
(24 weeks)
3,754.8 pigs
Below expected 15,229 pigs
Below expected
“Δ pigs A”
“Δ pigs B”
TTBP

41. Production Impact: Aggregate
Rapid Response

42. Prototype vs. INDEL PEDv
Prototype PEDv (124 herds)
Avg TTBP (3 SD) = 72% @ 12.6 wks
Net loss 2.6 pigs/sow
Avg 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/sow
Avg TTBP (100%) = 100% @ 6 wks
Net loss 0.9 pigs/sow

43. 4 more Indel herds
6000
5000
4000
3000
2000
1000
0
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
24 14 5 26 16 6 27 18 8 29 20 10 31 21 14 4 25 16 6 27 18 8 29 19 10 31 21 12
5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12
2013 2014

44. Reproductive, endemic infection, re-infection,
virulence??
PWM?
Repro?

45. Time to Stability
• 26 sites so far enrolled

46. Time to Stability
Weeks Post-Exposure
Week 4
Week 5
Week 6
Week 7
Week 8
Week 9
Week 10
Week 11
Week 12
Week 13
Week 14
Week 15
Week 16
Week 17
Week 18
Week 19
Week 20
Week 21
Week 22
Week 23
Week 24
Week 25
Week 26
Week 27
Site 1
Site 2
Site 3
Site 4
Site 5
Site 6
Site 7
Site 8
Site 9
Site 10
Site 11
Site 12
Site 13
Site 14
Site 15
Site 16
Site 17
Site 18
Site 19
Site 20
Site 21
Site 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 )

47. Risk factors for prolonged TTS

48. 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?

49. 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

51. 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)

52. 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.