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!!