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Impact of the environment on Impact of the environment on
pig respiratory disease pig respiratory disease transmission transmission
Research update on PRRSV/M.hyo biosecurity
S Otake, S Dee, A Pitkin, G Spronk, D Reicks, P Ruen, J Deen
AcknowledgementsAcknowledgements• PRRS CAP 1 and 2• National Pork Board (NPB)• Minnesota Pork Board (MPB)• University of Minnesota Swine Disease Eradication Center (UMN
SDEC) board members
• Drs. Scott Dee & Andrea Pitkin
• Pipestone Veterinary Clinic• Swine Vet Center• Fairmont Veterinary Clinic
• Dr. Steve Pohl (South Dakota State University)• Drs. Jean Paul Cano & Dale Polson (BIV)
• *Disclosure
IntroductionIntroduction
• PRRSV can be eliminated from farms– Dee and Molitor 1998, Torremorell and others 2000– Herd closure (>200 days) w/o intentional virus exposure– Depopulation
• Re-infection is a frequent event (Area spread)– Lager and others 2002
• PRRSV elimination is the long term goal in US• AASV: 2005• NPPC: 2010• NPB: 2011
• For “sustainable freedom from PRRSV” to be a reality, we must understand and manage the risk of area spread (especially airborne spread).
Known routes of PRRSV Known routes of PRRSV transmissiontransmission
Transmission routes Biosecurity interventions
Pigs and semen
People
Coveralls and boots
Needles
Fomites (lunch boxes, shipping containers, etc)
Insects (mosquitoes and house flies)
Transport
Aerosol
References
Yoon et al. 1993, Christopher-Hennings et al. 1995
Otake et al. 2002, Dee et al. 2012
Otake et al. 2002
Otake et al. 2002
Dee et al. 2003
Otake et al. 2003
Dee et al. 2004
Pitkin et al. 2010Otake et al. 2011
Quarantine and testing
Shower-in/outOne-night down time
Changing coveralls and boots
Changing needles
UV path-box, fumigation room,double-bagging, etc
Insect screen
Wash, disinfect and dry
Air filtration
© S. Otake
Aerosol spread of PRRSV: Aerosol spread of PRRSV: New KnowledgeNew Knowledge
• Variant dependent– Cho and others 2006-2007, Cutler and others 2011
• Risk factors– Population-based
• Dee and others 2010 – Meteorological
• Hermann and others 2007, Dee and others 2010
• Can occur over long distances– 4.7 km
• Dee and others 2009– 9.1 km
• Otake and others 2010
PRRSV (+) air samples
Otake and others, Veterinary Microbiology 2010
M.hyo (+) air samples
Air Filtration• Drivers:
– Protect the AI center• Produce PRRSV-free semen
– Protect the breeding herd• Produce PRRSV-free weaned pigs
• Literature review:– Proof of concept (Dee and others 2004)
– Alternative filter candidates (Dee and others 2009)
– Production region model (Pitkin and others 2009, Dee and others 2010)
– Field validation (Spronk and others 2010, Dee and others 2010, 2012)
1. Production Region Model1. Production Region ModelHypothesis: Sustainable freedom from PRRSV in a swine-
dense region is dependent upon air filtration.
– Project size and scope:• 1438 days (June 2006-Nov 2010)
• 4744 pigs utilized
• Multiple pathogens tested– PRRSV 184, 1-26-2, 1-18-2– M hyo
• 3 types of filters evaluated– Mechanical– Antimicrobial– Electrostatic
• 38,519 samples collected– Air, personnel, fomites, insects, transport, swine
Building 1PRRSV and M hyo-positive
source population
Building 3(treatment)
Building 2(control)
4m
120m
Predominant winddirection
Building 4(treatment)
4m
Dee and others, Virus Research 2010
Airborne transmission data across filter type
Pathogen Control MERV 16
MERV 14
Anti- microbial
Electrostatic
PRRSV 28/65
0/39(p <0.0001)
0/13(p <0.0001)
0/26(p <0.0005)
0/13(p < 0.0001)
M hyo 17/39 0/13(p <0.0001)
0/13(p <0.0001)
0/26(p <0.0001)
0/13(p < 0.0001)
Risk factors associated with Risk factors associated with airborne PRRSVairborne PRRSV
• Neighboring source population actively shedding virus via aerosols (p = 0.0002)
• Directional winds moving from a shedding source to an at-risk population (p = 0.0003)
• Winds of low velocity (1.4 to 1.9 m/s) with intermittent gusts (2.8 to 3.7 m/s) (p = 0.002)
Meteorological conditions Meteorological conditions associated with airborne PRRSVassociated with airborne PRRSV
• Cool temperatures: -2.6 to 4.80 C (p = 0.01)
• High relative humidity: 77 to 82% (p = 0.003)
• Rising pressure: 979 to 984 hPa (p = 0.003)
• Low sunlight levels: (p = 0.04)
High risk Low risk
2. Field Validation2. Field Validation• Objective
– Test the efficacy of air filtration for reducing the risk of new PRRSV introduction to large breeding herds in swine dense regions
• Hypothesis– Re-infection is less likely to occur in filtered versus non-filtered herds
• Team– University of Minnesota– Pipestone Veterinary Clinic– Swine Vet Center– Fairmont Veterinary Clinic
• Design– Treatments (filtered) & control (non-filtered) herds– Project period: Sept 08-Jan 2012
• Selection criteria– > 2400 sows– > 3 external virus introductions over the past 4 years– > 4 pig sites within 4.7 km radius of candidate herd– Historical application of validated biosecurity protocols
• Outcomes measured– External virus introduction– Cost-benefit
National Hog Farmer, April 2012
ResultsFiltered vs. Non-filtered herds
Category
# farms
Cumulative days
# New Infections Interval
Infections per farm
Filtered 24 16,593 8 2074 d .33
Non-filtered 33 29,533 89 336 d 2.7
Dee et al. (2012) Viruses, 4(5), 654-662
1. The likelihood of a new PRRSV infection was significantly higher (p < 0.01) in non-filtered herds versus filtered herds.
2. The odds of a new PRRSV infection were 8x higher (p < 0.01) before filtration than after filtration.
3. The median time to new PRRSV infections in filtered herds (30 months) was significantly lower ( p < 0.01) than in non-filtered herds (11 months).
Conclusion: Filtration significantly reduces the risk of new PRRSV infections.
Change in nursery mortality pre- and post-filtration of study herds
Pre-filtration (PRRSV+)
Post-filtration (PRRSV-)
Flow 1 8.3% 2.6%
Flow 2 19.8% 1.9%
Flow 3 13.2% 1.6%
ConclusionsConclusions1. Long distance airborne spread of PRRSV has been
documented.
2. It requires specific risk factors and conditions which are now well understood.
3. Air filtration has proven to be effective at reducing the risk of external PRRSV introduction under highly challenging conditions.
4. These data have catalyzed wide-spread adaptation of filtration across the US swine industry.– > 200,000 sows under filtration by Fall 2011 and more…– Global application (Asia)
ImpactImpact
• For the first time since its emergence, “sustainable freedom from PRRSV” in a swine-dense region is now possible to achieve and maintain for significant periods of time.
• The importance of all the basic biosecurity practices for people, fomites, transport, etc. should not be neglected.
PRRS control/elimination:PRRS control/elimination:A model of global/domestic collaboration!
Example1: SDEC Japan• A group of veterinarians from JASV
(Japanese Association of Swine Veterinarians)• A board member of SDEC (Swine Disease Eradication Center),
University of Minnesota
Example 2: P-JET• PRRS elimination task force of Japan• A group of veterinarians and researchers in Japan
THANK YOU!!THANK YOU!!