Exploring practices to reduce time to PRRS stability

Daniel Linharesa, Carl Betlachb, Hunter Baldreyb, Bob Morrisonb

aVeterinary Diagnostic and Production Animal Medicine, Iowa State UniversitybVeterinary Population Medicine, University of Minnesota

Summary: data from 168 breeding herdsProject to reach Stable: • 60 to 80% success rate• 24 to 60 weeks to reach the 4th negative testTTS and probability to reach Stable were better in the 2009-2013 cohort (61 herds) compared to the 2014-2016 cohort (107 herds):• Herd closure? Whole-herd exposure? PRRSv itself?TTS at farrowing: • 20 weeks (best= 8wks) answer in farrowing room?Wean down project

Early TTS is possible

Topics

• A brief review of the 2009-2013 TTS / TTBP work• Update on the 2014-2016 TTS/TTBP work (1-7-4 farms)• Update on TTS at farrowing• Wean-down project• Summary

comparisons

2009-2013 study

Eligibility criteria Acutely infected breeding herds Load-close-expose with resident virus or MLV vaccine Intention to achieve stabilityNotes: ~ 50% infected with 1-4-4 ~ 50% with prior history of PRRS detection (past 3 years) 61 Farms, 16 systems

0 10 20 30 40 50

LVI

MLV

Time (weeks)

Trea

tmen

t

PRRSv Load-Close-Homogenize programs: 1-year timeline

TTSTTBPSilent PRRS (!)

TTSTTBP

Silent PRRS

virus shedding no signs

Linhares, Cano, Torremorell, Morrison, 2013 Preventive Veterinary Medicine

2009-2013 study

Major findings Shorter TTS: LVI, System, prior infection history Shorter TTBP / Total Loss: MLV, System, prior history

Other important findings: Intermittent pattern of PRRS detection by PCR (30 pigs) 80% farms adopting LCE reached TTS, 72% reached

provisional negative status

2014-2016 study: Eligibility criteria

SHMP breeding herds infected with 1-7-4 PRRSv Agreement to test at least 30 litters (6 x 5 sera) at least 4

consecutive times to achieve stable No requirement to implement herd closure or exposure

Notes: All infected with 1-7-4 virus107 farms, 5 Systems

Median TTS (95th confidence interval):Best: 37 (32 – 42) weeksLonger: 44 (39 – 51) weeks

2016 study TTS by SystemTT

S Pr

obab

ility

Median TTS (95th confidence interval):2013 study 38.3 (35 – 42) weeks2016 study 44 .0 (41 – 52) weeks

2013 cohort achieved TTS sooner than 2016 herds1/3 of 2016 herds did not reach TTS by 52 weeks

TTS

Prob

abili

ty

TTS

Prob

abili

tyMLV herds: 2013 herds tended to reach Stable faster than 2016 herds

Median TTS: no significant difference2013 study 44 weeks2016 study 51 weeks

Median TTBP (95th confidence interval):2013 study 25.1 (23 – 27) weeks2016 study 17.8 (14 – 20) weeks

TTBP

Pro

babi

lity

2016 cohort achieved TTBP ~7 weeks sooner than 2013

All herds: closure was associated with faster TTS

44weeksTTS50

38 weeks

TTBP50

Success rate to reach Stable

Comparisons between the 2013 and 2016 studies (TTS @ last testing)

Early ones:24-28 weeks

2013 2016

18 weeks

2016

25weeks

2013

80%49/61

2013

62%67/107

2016

How to replicate shorter TTS with high success rate?

TTS at Farrowing

Betlach & Morrison, 2016

TTS @ FarrowingMedian time: 21.2 weeksRange: 8 to 32 weeks

PRRSv RNA RT-PCR from blood, tail blood swabs, or placental umbilical cord serum (PUCS)

Litters < 24 hrs old No cross-fostering

Wean-down project

Model by Carles Vilalta & Morrison: wean-down reduces TTS Breeding herds are invited to enroll$1,000/herd from BI grant to subsidize Dx test costs

Goal is to enroll 30 wean-down herds and compare their TTS to 30 matched non wean-down herds. Contact Dr Bob Morrison (BobM@umn.edu) to enroll.

Summary: data from 168 breeding herds

Project to reach Stable: • 60 to 80% success• 24 to 60 weeks

TTS at farrowing: • 20 weeks (best= 8wks)

answer in farrowing room?

Wean down projectEarly TTS is possible

Summary: data from 168 breeding herds

TTS and probability to reach Stable were better in the 2009-2013 cohort (61 herds) compared to the 2014-2016 cohort (107 herds):

• Herd closure?• Whole-herd exposure?• PRRSv itself?

Wean-down / internal biosecurity to decrease TTS?

Thank you

Acknowledgements SHMP participants for collaborating Boehringer Ingelheim for funding SHIC (swinehealth.org) for funding

Daniel LinharesVDPAM, Iowa State UniversityLinhares@iastate.edu

Bob MorrisonUniversity of MinnesotaBobM@umn.edu