Summary On Recent Time-to-PRRS-Stability Research - Dr. Daniel Linhares, from the 2016 Allen D. Leman Swine Conference, September 17-20, 2016, St. Paul, Minnesota, USA. More presentations at http://www.swinecast.com/2016-leman-swine-conference-material

1. Exploring practices to reduce time
to PRRS stability
Daniel Linharesa, Carl Betlachb, Hunter Baldreyb, Bob Morrisonb
aVeterinary Diagnostic and Production Animal Medicine, Iowa State University
bVeterinary Population Medicine, University of Minnesota

2. Summary: data from 168 breeding herds
Project to reach Stable:
• 60 to 80% success rate
• 24 to 60 weeks to reach the 4th negative test
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?
TTS at farrowing:
• 20 weeks (best= 8wks) answer in farrowing room?
Wean down project

3. Early TTS is possible

4. 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

5. 2009-2013 study
Eligibility criteria
 Acutely infected breeding herds
 Load-close-expose with resident virus or MLV vaccine
 Intention to achieve stability
Notes:
 ~ 50% infected with 1-4-4
 ~ 50% with prior history of PRRS detection (past 3 years)
 61 Farms, 16 systems

6. 0 10 20 30 40 50
LVI
MLV
Time (weeks)
Treatment
PRRSv Load-Close-Homogenize
programs: 1-year timeline
TTS
TTBP
Silent PRRS (!)
TTS
TTBP
Silent PRRS
 virus shedding
 no signs
Linhares, Cano, Torremorell, Morrison, 2013 Preventive Veterinary Medicine

7. 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

8. 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 virus
107 farms, 5 Systems

9. Median TTS (95th confidence interval):
Best: 37 (32 – 42) weeks
Longer: 44 (39 – 51) weeks
2016 study TTS by SystemTTSProbability

10. Median TTS (95th confidence interval):
2013 study 38.3 (35 – 42) weeks
2016 study 44 .0 (41 – 52) weeks
2013 cohort achieved TTS sooner than 2016 herds
1/3 of 2016 herds did not reach TTS by 52 weeks
TTSProbability

11. TTSProbabilityMLV herds: 2013 herds tended to reach Stable faster than 2016 herds
Median TTS: no significant difference
2013 study 44 weeks
2016 study 51 weeks

12. Median TTBP (95th confidence interval):
2013 study 25.1 (23 – 27) weeks
2016 study 17.8 (14 – 20) weeks
TTBPProbability
2016 cohort achieved TTBP ~7 weeks sooner than 2013

13. All herds: closure was associated with faster TTS

14. 44
weeksTTS50
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
25
weeks
2013
80%
49/61
2013
62%
67/107
2016

15. How to replicate shorter TTS with
high success rate?

16. TTS at Farrowing
Betlach & Morrison, 2016
TTS @ Farrowing
Median time: 21.2 weeks
Range: 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

17. 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.

18. 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 project
Early TTS is possible

19. 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?

20. Thank you
Acknowledgements
 SHMP participants for collaborating
 Boehringer Ingelheim for funding
 SHIC (swinehealth.org) for funding
Daniel Linhares
VDPAM, Iowa State University
Linhares@iastate.edu
Bob Morrison
University of Minnesota
BobM@umn.edu