dr. daniel linhares - summary on recent time-to-prrs-stability research
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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
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
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
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
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