Novel Sampling Strategies for Piglets-from Testicles to Teats! - Dr. Carlos Vilalta, from the 2017 Allen D. Leman Swine Conference, September 16-19, 2017, St. Paul, Minnesota, USA. More presentations at http://www.swinecast.com/2017-leman-swine-conference-material

1. Novel sampling strategies for
piglets - from testicles to teats!
Carles Vilalta, Juan Sanhueza,
Montse Torremorell, Bob Morrison

2. Introduction
• There is a need to have more sensitive methods to
detect PRRSV in low prevalence situations
• We require cheaper and quicker ways of sampling
• Castration and tail docking are part of routine
chores at the farm
• Sampling the environment has been shown to be a
sensitive approach for certain diseases (i.e PEDV)

3. Objectives
• To evaluate novel sampling strategies to
detect PRRSV at processing:
– Processing fluids (PF), environmental samples
and sampling of the sow
• Sensitivity and specificity
• Effect of parity
• Effect of time from infection

4. PROCESSING FLUIDS
PART 1

5. Outbreak
Sampling weeks
Weeks Post Outbreak
1 2 3 4 5 6 7 8
3/24/2017 Virus inoculation
2 5 8 11 14 17 20 23
Study design
3/02/2017 7/26/2017
02/22/2017

6. Study design
Processing
Fluids
(per litter)
Gold Standard
10 litters/week
Blood from all piglets in litter

7. Outbreak
Sampling weeks
Weeks Post Outbreak
1 2 3 4 5 6 7 8
3/02/2017
2 5 8 11 14 17 20 23
Study design
Extended
processing fluids
sampling
3/24/2017 Virus inoculation
02/22/2017

8. Weeks Post Outbreak
Total
2 5 8 11 14 17 20 23
Piglets 107 128 118 102 124 112 121 127 939
Litters /
PF
9 10 10 9 10 9 10 10 77
PF
Extended
9 10 10 25 46 29 25 21 175
Number of samples collected

9. Sensitivity and specificity of processing fluids
Positive Negative
Positive 20 4
Negative 4 49
Processing fluids status
Litterstatus
Se: 83%
(63-95%)
Sp: 92%
(82-98%)
Kappa:
0.76 (0.53-0.98)
Good agreement
Ct cut off value: 37.5

10. Percent positive samples since outbreak
N=77
N=939

11. Percent positive samples since outbreak
N=175
N=77

12. Positivity of processing fluids positive
per parity
N=175
*
p<0.05

13. Positivity of processing fluids by parity
and week
N=175

14. Positive Ct values per week

15. Effect of dilution of processing
fluids on Ct values

16. ENVIRONMENTAL SAMPLING
PART 2

17. Outbreak
Sampling weeks
Weeks Post Outbreak
1 2 3 4 5 6 7 8
3/24/2017 Virus inoculation
2 5 8 11 14 17 20 23
Study design
3/02/2017 7/26/2017
02/22/2017

18. Study design
Gold Standard
Udder
Surfaces
10 litters/week
3 Airborne
particle
deposition
Pictures: Jorge Garrido
Blood from all piglets in litter

19. Positive Negative
Positive 12 12
Negative 4 49
Surface wipes status
Litterstatus
Se: 50%
(29-71%)
Sp: 92%
(89-98%)
Kappa:
0.47 (0.25-0.68)
Moderate
Sensitivity and specificity of surface wipes
Ct cut off value: 37.5

20. Positive Negative
Positive 10 14
Negative 1 52
Udder wipes status
Litterstatus
Se: 42%
(22-63%)
Sp: 98%
(90-100%)
Kappa:
0.47 (0.27-0.66)
Moderate
Ct cut off value: 37.5
Sensitivity and specificity of udder wipes

21. Comparison between surface wipes
and udder wipes
S U S U S U S U S U S U S U S U
NA NA
2 5 8 11 14 17 20 23
Weeks Post Outbreak
S: Surface U: Udder

22. Airborne particle deposition
NA NA NA NA NA NA
2 5 8 11 14 17 20 23
Weeks Post Outbreak

23. 0%
20%
40%
60%
80%
100%
0 5 10 15 20 25
%positivesamples
Weeks Post Outbreak
Serum
PF
PF ext
Surf
Udder
Overall comparison by sample type
overtime

24. Comparisons by sample types
Kappa
(95%CI)
Se
(95%CI)
Sp
(95%CI)
Sequencing
Possible
Processing
fluid
0.76
(0.53-0.98) 83%
(63-95%)
92%
(82-98%) Yes
Good
Surface
0.47
(0.25-0.68) 50%
(29-71%)
92%
(89-98%) Yes
Moderate
Udder
0.47
(0.22-0.66) 42%
(22-63%)
98%
(90-100%) Yes
Moderate

25. Conclusions
- Processing fluids are an effective sample to detect PRRSV in
piglets, including after significant time since outbreak (~ 6
months) specially in litters from young parity sows.
- Environmental samples have lower sensitivity than processing
fluids.
- One limitation of this study is that only samples from one farm
are represented

26. Discussion
- Processing fluids are a very sensitive
sample to detect PRRSV at litter level,
however…
- No difference in number of positives obtained between
males and females
- No noticeable fluid coming out of the tails.
0
5
1 2 3 4 5 6 7 8 9 10 11 12
Litters
Positive piglets
Positive piglets per litter

27. Discussion
- Processing fluids appear to be a good
tool to define status of the herd: positive
or negative
- We did not increase sensitivity by increasing
sample size
- Pooling processing fluids from various litters may
reduce our sensitivity at high Ct values, however it
may increase sensitivity at herd level
- Parity effect (Cano et al., 2008)

28. Take Home Messages
- The use of processing fluids is a sensitive
tool for sampling breeding herds.
- Pooling of processing fluids may reduce
our sensitivity at higher Ct. However, it will
allow us to sample more litters.
- Target young parities for PRRSV sampling

29. Acknowledgements
• Deb Murray
• My Yang
• Julio Alvarez
• Albert Rovira
• Jorge Garrido
• Alejandro Casanova
• Shaoqin Wu
Funding

30. Carles Vilalta
cvilalta@umn.edu
Though Morrison has remained in
academia for most of his career, he
has stressed to his team and his
students the importance of carrying
on the Leman legacy: “Do work that
matters.”
National Hog Farmer