Dr. Andreia Arruda - Investigation of Land Coverage and Elevation as Risk Factors for PRRS Breaks
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Transcript of Dr. Andreia Arruda - Investigation of Land Coverage and Elevation as Risk Factors for PRRS Breaks
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Investigation of land coverage and elevation as risk factors for
PRRS breaks
Andreia Arruda, DVM PhDUniversity of Minnesota
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BackgroundCumulative PRRS incidence 2009-2017 (SHMP)
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Background
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Background
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Background
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Background
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Objective
Investigate whether land elevation and coverage are associated with PRRS breaks
- Account for important factors of interest
- Use data from swine sites spread across the country
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Methods
Data source: SHMP (n=706 sow herds), 2009-2016
Variables of interest: • Terrain elevation• Land coverage• Swine density• Geographical region• Herd size
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MethodsDensity of swine sites participating in the SHMP
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MethodsDensity of swine sites (FAO, modelled; 2005)
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Elevation• The height of a terrain
– Absolute number – altitude (meters above sea level)– Relative number – slope, steepness as compared to
other features in the area
runrise
Slope = riserun
e.g. 20 𝑓𝑓𝑓𝑓100 𝑓𝑓𝑓𝑓
= 0.2 or 20%
86m
80m86m
1m = 3.3 ft
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12345
SlopePublished 2007-02-16NASA Shuttle Radar Topographic Mission (SRTM), 2006USGS Geological Survey (GTOPO30), 2002
1- 2% (8%)2-5% (35%)5-8% (43%)8-16% (10%)16-30% (5%)30-45% (0)> 45% (0)
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AltitudeThe CGIAR Consortium for Spatial InformationNASA Shuttle Radar Topographic Mission (SRTM), 2006USGS Geological Survey (GTOPO30), 2002
1: <185m (25%) 2: 185 - 316m (25%)3: 317 - 391m (25%)4: > 391m (25%)
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Land Coverage Joint Research Centre (European Commission)Global Land Cover 2000 Project (GLC2000)
1: cultivated and managed areas (67%)2: shrubs/ herbaceous cover (e.g. pasture) & others (14%)3: tree cover, needle-leaved or mixed (9%)4: tree cover, deciduous broad-leaved (11%)
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Methods
Outcome of interest: number of breaks
Statistical model: Multilevel mixed-effects Poisson regression
• Backwards stepwise approach• Random effect for production system• Statistical significance declared at P < 0.05
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Results
• Mean 1.4 outbreaks per year per site• 40% farms never reported a break
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Variable¶ IRR P-value
Density 1.46 <0.001*
N animals 1.30 0.001*
Land coverage Shrubs, herbaceous 0.70 0.04*
Needle-leaved trees 0.56 0.003*
Broad-leaved trees 0.42 0.009*
Slope 2-4% 1.01 0.95
5-8% 0.77 0.10
9-16% 0.44 0.001*
17-30% 0.18 0.006*
Region MN/IA 1.59 0.001*
NC 0.83 0.60
NE 0.70 0.06
Other 0.49 0.001*
OK 1.28 0.38
PA 0.58 0.36
Results
¶Refs- low density, low N animals, land coverage as cultivated/ managed areas, slope 1% or <, region IL
Results should be interpreted with
caution due to the cross-sectional
nature of the data
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• Large number farms across many US regions
• Land inclination– Airborne transmission– Proxy for other factors
• Vegetative filters
Discussion
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Take-home messages
- We investigated whether land elevation and coverage are associated with PRRS breaks.- “Highly inclined terrains” were associated with
fewer breaks- Presence of shrubs and trees were associated with
fewer breaks compared to cultivated areas
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Acknowledgements
University of Minnesota, College of Veterinary MedicineB. Morrison, C. Vilalta, A. PerezSHICSHMPSwine veterinarians and producers that share data
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Thank [email protected]