- An epidemiological investigation of an HPAI outbreak in the US Midwest in 2015 identified risk factors for infection through a case-control study of layer farms. Factors associated with increased risk included proximity to rendering trucks, garbage trucks, and having company service visits. - A modeling study evaluated the role of aerosol transmission between commercial turkey farms in Minnesota. It found cumulative exposure to plumes from infected farms over 6-11 days was the strongest predictor of infection, supporting some role of aerosol spread. - Air sampling on turkey and layer farms in Minnesota detected virus on some farms up to 1 km from infected barns, suggesting aerosol spread may occur over shorter distances. Environmental factors like proximity

1. Epidemiologic Investigations
of HPAI and Disease Prevention
Brian McCluskey, DVM, MS, PhD, Dip. ACVPM
USDA, APHIS,Veterinary Services

2. Epidemiologic
Investigations
• Field-based observational studies
• Geospatial analyses
• On-farm sampling efforts
• Phylogenetic investigations
“The study of the distribution
and determinants of disease in
populations with the goal of
using those determinants
to prevent disease”

3. Outbreak
Investigation:
Case Series
• 81 turkey farms in IA, MN, ND, SD andWI
– 63 meat production
– 11 breeder farms
– 6 raising breeder candidates
– 1 unknown type
• Developed clinical signs between March
30 and May 2, 2015.
Animal and
Plant Health
Inspection
Service
Veterinary
Services
HPAI Investigation - Questionnaire
INSTRUCTIONS
The purposes of these investigations are to assess potential pathways of initial introduction of HPAI
viruses onto commercial poultry operations and potential lateral transmission routes of HPAI viruses
from infected premises to noninfected premises.
Following confirmation of an HPAI virus introduction into a commercial flock, an investigation should be
initiated as soon as possible, no later than 1 week following detection. The investigator(s) assigned
should be integrated into other response activities but their primary focus is on completion of the
introduction investigation.
Analysis conducted by Dr. Andrea Beam and Dr. Dave Dargatz,Veterinary Services

4. Biosecurity
Number Respondents Level or Response Percent Farms
House with family on property 81 Yes, common drive 38
Yes, no common drive 22
No 40
Signage (“no admittance” or “biosecure area”) 80 83
Gate to farm entrance 79 Yes, locked 9
Yes, not locked 18
No 73
Farm area fenced in 81 11
Freq veg. mowed (per month) 81 < 4 40
4 + 60
Facility free of debris/trash 81 89
Wash/spray area for vehicles 81 46
Designated parking workers/visitors 80 49
Changing area for workers 81 Yes, shower 27
Yes, no shower 46
No 27
Workers wear dedicated coveralls 81 73
Workers wear rubber boots or Boot covers 81 100
Barn doors lockable 81 Yes, routinely locked 40
Yes, not routinely lock 22
No 38
Foot pans at barn entrances 81 Yes, in use 99
Footbath type 81 Dry 12
81 Liquid 98
Ante area 81 98
Rodent bait station 81 Yes, checked q 6 weeks 95
Fly control 81 41
Raccoons, possums, foxes seen in or around barns 81 28
Wild turkeys, pheasants, quail seen around poultry 81 26
Biosecurityaudits 81 43

5. Equipment Number
Respondents
Level or Response Percent Farms
Farm specific (NOT shared with other farms) 75 Company vehicles/ trailers 65
77 Feed trucks 19
80 Gates/panels 91
80 Lawn mowers 63
78 Live haul loaders 8
68 Poultry trailers 31
72 Pre-loaders 15
79 Pressure sprayer/washer 57
77 Skid-steer loader 61
67 Tillers 87
70 Trucks 56
58 Other 66

6. Wild BirdCharacteristics
Number
Respondents
Level or Response Percent Farms
Wild birds around farm 78 Waterfowl
63
79 Gulls
33
78 Small perching birds
96
78 Other water birds
15
78 Other birds
28
Houses bird proof
79 62
Wild birds seen in house
81 35
Birds seen year round
77 90
Seasonality to presence of some birds
79 84
Bird location
76 Away from facilities 49
77 On farm, not in barns 66
76 On farm, in barns 26

7. Case-Control
Study - Layers • Study included all detected cases as of
May 15, 2015 in Iowa and Nebraska
• Total of 28 cases and 31 controls
• Survey administered to site managers
• At risk period was two weeks prior to
detection
• Controls were matched by at risk period
• Factors examined at farm and barn level
Analysis conducted by Lindsey Garber and Kathe Bjork,Veterinary Services

8. Case Control Study - Layers
FACTOR*
Farm Level
Percent
case farms
Percent
control
farms
Odds Ratio P-value Average
attributable
fraction
In an existing control zone 50 10 32.0 .002 31.7%
Rendering trucks near barns 29 3 22.3 <.001 14.0%
Garbage trucks near barns 61 23 14.7 <.001 28.1%
Visitors change clothes 77 93 0.08 /
12.6**
.01 7.6%**
Company service person visit in past
14 days
50 19 5.0 <.001 15.0%
*Reference level = absence of factor ** do not change clothes

9. Case Control Study - Layers
FACTOR*
Barn level
Percent
case farms
Percent
control
farms
Odds Ratio P-value Average
attributable
fraction
Barn entry with a hard surface entry pad
cleaned and disinfected
28.6 53.6 0.16/6.9** 0.01 33.7%**
Disposing of dead birds near a barn
(within 30 yards)
60.7 35.5 2.8 0.002 20.2%
Having ceiling or eaves inlet ventilation
type (compared with curtain, sidewall or
tunnel types)
48.2 67.7 0.33/3.0** <0.001 23.4%**
*Reference level = absence of factor **absence of factor

10. Biosecurity
“It is frustrating how difficult it is to prove
scientifically which biosecurity efforts work
or are the most important or effective”
Dr. Francisco Revriego
European Commission
“Biosecurity is inconvenient”
Dr.John Glisson
U.S. Poultry and Egg Association

11. Wind related
spread of EA/AM
H5N2 HPAI virus
• Evaluate the role of aerosol
transmission between commercial
turkey flocks in Minnesota (n=98)
• Used EPA’s AERMOD modeling
system
• Wind speed, direction data
collected from 105 National
Weather Service stations across
Minnesota
• Other meteorological parameters
were also collected
Analysis conducted by Sasi Malladi (Univ of Minn),Todd Weaver, Amy Delgado,
Phillip Riggs and Andrew Fox,Veterinary Services

12. Figure 1. Aerosol exposure regions representing a 0.01 (lighter region) and 0.05 (darker region)
daily likelihood of transmission from an infected premises at 4 mph (green) and 32 mph wind
speeds (brown).

50. Epidemiological
Analyses
• Plumes of virus–associated particles
were modeled for all infected farms
based on average wind speed and
direction over various time frames.
• Case-control study examining effects of
cumulative daily exposure to modeled
plumes accounting for age and and
susceptibility of birds on each farm.
• Repeated measures examining daily and
cumulative risk of disease associated
with modeled plumes.

51. Results • Cumulative exposure of a farm to
multiple plumes over a 6-11 day period
was the most stable predictor of
increased odds of disease.
• Proximity to other infected farms had a
consistent association with increased
odds of becoming a case in all three
analyses.
• Given current data it is difficult to rule in
or out the contribution of aerosol
transmission of farms up to 3.5 km from
a shedding farm.

52. On-farm Air Sampling
Sampling and analysis conducted by MontseTorremorell et al., Univ of Minnesota

53. On-farm Air Sampling
Inside 5 m 70-150 m 500-1000 m
Turkeys
Positive 40 (36%) 7 (21%) 0% NT
Suspect 26 (23%) 17 (50%) 8 (38%) NT
Negative 45 (41%) 10 (29%) 13 (62%) NT
Layers
Positive 28 (78%) 22 (24%) 1 (4%) 0 (0%)
Suspect 8 (22%) 16 (18%) 9 (32%) 8 (13%)
Negative 0 (0%) 52 (58%) 18 (64%) 54 (87%)
Total
Positive 68 (46%) 29 (23%) 1 (2%) 0 (0%)
Suspect 34 (23%) 33 (27%) 17 (35%) 8 (13%)
Negative 45 (31%) 62 (50%) 31 (63%) 54 (87%)
Total 147 (100%) 124 (100%) 49 (100%) 62 (100%)
Ct <35: positive; Ct 35-40: suspect; Ct >40 negative.

54. Environmental
risk factors
related spread
of EA/AM H5N2
HPAI virus
• State-wide dataset of poultry operations
in Minnesota was merged with records
from EMRS.
• Included information on production type
and the location of the farm in latitude
and longitude.
• Potential risk factors considered were
poultry density, distance to nearest body
of water, density of corn (within 0.5, 1 and
3 km) and distance to major highways.
• Logistic regression and boosted
regression tree analyses were conducted.
Analysis conducted by Amy Delgado, Phillip Riggs and Andrew Fox,Veterinary Services

55. Results
Risk Factor Levels Adjusted
Odds Ratio
95% Conf. interval P-value
Species Chicken
Turkey
---
9.91 (3.00-32.37) <0.001
Distance to nearest
infected neighbor
>10 km
<10 km
---
10.67
---
(5.75, 19.8) <0.001
Corn density (acres)
within 3 km
<1191 acres
1192-1999 acres
2000-2739 acres
>2740 acres
---
5.15
8.42
12.12
---
(1.63-12.29)
(2.80-25.34)
(4.18-35.13) <0.001

56. Results
Predictor Relative Influence
Distance to nearest infected neighbor 43.5%
Corn acreage within 3 km 14.8%
Distance to highways 71, 12, or 4 12.8%
Distance to nearest water 10.4%
Distance to any major highway 7.9%
Poultry density in county 6.8%
Production type of operation 2.4%
Species present on farm (chicken vs turkey) 0.4%

57. 57
HPAI/LPAI Outbreak
Indiana – January 2016

58. • Objective
– Identify potential farm- and barn-level risk
factors for AI H7N8 on turkey farms in Indiana
during the 2016 outbreak
• Sample
– All case farms (n=9)
– Control farms from surrounding geographic
area in the disease control area (n=30)
58
Case-Control Study

59. • Differences identified between case farms
and barns compared to controls
• Proximity to dead bird disposal and litter
compost areas were risk factors in
previous studies
• Higher percentage of case farms had
visitors entering barns
Case-Control Study Highlights

60. FACTOR Percent case farms Percent control farms
Brooders raised on farm 33 62
Wild mammals around
poultry barns during the
14‐day risk period
88 41
Visitor type during 14-day risk
period:
Veterinarian
Service person
Catch crew
13
88
25
0
72
7
Pond within 350 yd 100 60
Results – Farm Level

61. Factor Percent case
barns
Percent control
barns
Type of bird:
Brooder
Grower
0
100
26
74
Age of birds (weeks):
<8
8 – 13
14+
0
25
75
44
15
41
People who entered barn during 14‐day risk period:
Veterinarian
Service person
Occasional worker
Any
29
88
38
100
4
61
21
68
Hard surface entry pad cleaned and disinfected 33 68
Median distance to dead bird disposal area (yds) 59 100
Results – Barn Level

62. • County-level analysis – Dubois and
surrounding counties
• Observed weather patterns 6 weeks prior
to outbreak
62
Geospatial Assessment for H7N8
HPAI/LPAI Indiana Outbreak

63. • Mean high
temperature
(50.88˚F)
• Warmer than
last 2 years
• Mean low
temperature
(30.04˚F) –
above
freezing
Temperature

64. • 2016 precipitation greater than 2015, less than 2014 –
perhaps not single factor of importance
• Paired together – temperature & precipitation
conducive to virus survival in the environment
Precipitation

65. • H5N2 2015 Minnesota
outbreak – cropland may
contribute to presence of
infected waterfowl
• Cropland coverage in SW
Indiana counties ranged
from 3.5-78.0%
• Cropland did not appear
to differ between the
infected and uninfected
counties
• Dubois County on lower
range of wetland and
open waters; not
considered a factor
Percent
Cropland
Percent
Wetland
Cropland & Wetland/Open Water

66. • Virus circulating in
waterfowl must find
susceptible poultry
population
• Dubois County has higher
density of poultry compared
to surrounding counties
Turkey & Chicken
inventory by county
Susceptible Population

67. Questions?