Impact of the environment on pig respiratory disease transmission Impact of the environment on pig respiratory disease transmission Research update on PRRSV/M.hyo biosecurity S Otake, S Dee, A Pitkin, G Spronk, D Reicks, P Ruen, J Deen

Acknowledgements 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

Introduction 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 transmission Transmission routesBiosecurity 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 Otake et al. 2002, Dee et al Otake et al Dee et al Otake et al Dee et al Pitkin et al Otake et al Quarantine and testing Shower-in/out One-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: New Knowledge Variant dependent –Cho and others , 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 Model Hypothesis: S ustainable 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, , –M hyo 3 types of filters evaluated –Mechanical –Antimicrobial –Electrostatic 38,519 samples collected –Air, personnel, fomites, insects, transport, swine

Building 1 PRRSV and M hyo-positive source population Building 3 (treatment) Building 2 (control) 4m 120m Predominant wind direction Building 4 (treatment) 4m Dee and others, Virus Research 2010

Airborne transmission data across filter type PathogenControl MERV 16 MERV 14 Anti- microbial Electrostatic PRRSV28/65 0/39 (p <0.0001) 0/13 (p <0.0001) 0/26 (p <0.0005) 0/13 (p < ) M hyo17/39 0/13 (p <0.0001) 0/13 (p <0.0001) 0/26 (p <0.0001) 0/13 (p < )

Risk factors associated with airborne PRRSV Neighboring source population actively shedding virus via aerosols (p = ) Directional winds moving from a shedding source to an at-risk population (p = ) 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 associated with airborne PRRSV Cool temperatures: -2.6 to 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 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

Results Filtered vs. Non-filtered herds Category # farms Cumulative days # New InfectionsInterval Infections per farm Filtered 24 16, d.33 Non-filtered 33 29, d 2.7 Dee et al. (2012) Viruses, 4(5), 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 18.3%2.6% Flow 219.8%1.9% Flow 313.2%1.6%

Conclusions 1. 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)

Impact 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

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