Natural Infection, Immunity & Prevalence of PCV2 - Dr. Michael Murtaugh and Dr. Cheryl Dvorak, University of Minnesota, USA , from the Boehringer Ingelheim Pre-AASV Conference, February 28, 2014 - Dallas, TX More presentations at http://www.swinecast.com/2014-boehringer-ingelheim-aasv

1. Natural Infection, Immunity & Prevalence of PCV2
Michael Murtaugh and Cheryl Dvorak
University of Minnesota, USA
Acknowledgements
Charles Haley and Eric Bush, USDA-APHIS
Suresh Tikoo, VIDO
Sponsors
University of Minnesota SDEC
Boehringer Ingelheim Vetmedica, Inc.

2. Canada 1999
mPCV2b
PCV2a
2001-2013
PCV2b
2003-2013
2006-2013
China 2003
2012-2013
MN VDL Sequencing
917 Isolates
0.02
0.5
5
50
500
1 3 5 7 9 11 13 15Series1
1999
2001
2003
2005
2007
2009
2011
2013
NumberofSequences
Year of Isolation
490

3. Swine Finishing Herds in USA (n=187, pigs >20 weeks)
Viremia
PCV2 >99% of Herds Positive
Antibody
>99% of Herds Positive
Average PCV2 titer >104 copies per ml
0
50
100
Within Herd Prevalence
Frequency(NumberofFarms)
0
100
200
300
400
500
600
2 3 4 5 6 7 8 9
PCV2 DNA copies/ml (log )
Frequency(numberofanimals)
0
20
40
60
80
0-10 11-20 21-30 31-40 41-50 51-60 61-70 71-80 81-90 91-100
Within Herd Prevalence
Frequency(NumberofFarms)
In 2005, there was no PCVAD in the USA
Porcine Circovirus in 2006, USA

4. Porcine Circovirus in 2006 Pre-PCVAD, Pre-Vaccines
Swine Finishing Herds in USA (n=187, pigs >20 weeks)
Viremia
PCV2 >99% of Herds Positive
Antibody
>99% of Herds Positive
Average PCV2 titer >104 copies per ml
0
50
100
Within Herd Prevalence
Frequency(NumberofFarms)
0
100
200
300
400
500
600
2 3 4 5 6 7 8 9
PCV2 DNA copies/ml (log10)
Frequency(numberofanimals)
0
20
40
60
80
0-10 11-20 21-30 31-40 41-50 51-60 61-70 71-80 81-90 91-100
Within Herd Prevalence
Frequency(NumberofFarms)
Puvanendiran et al. 2011.
Virus Res 157:92-98.

5. 0
50
100
150
200
250
300
350
400
A B AB -
286
386
95
233
N=1000
PCV2a PCV2b PCV2a+
PCV2b
Negative
29%
39%
9%
23%
PCV2b in 48% of pigs
PCV2a in 38% of pigs
: in 2006
PCV2
a
PCV2
b
qPCR
Rowland et al.

6. AB
B
ANumberperbin
CT value
X=35.3
X=35.9
X=34.4
Level of Viremia is
Not Affected by
Genotype of
Infecting Viruses
Infection with
PCV2a=PCV2b=
PCV2a+2b

7. • Pigs at finishing are viremic
• Antibody is not controlling infection
• What is the source of infection?
When do Pigs get Infected?

8. Sows are viremic
Virus in Colostrum Virus in Oral fluids
Pre-farrowing Sows are Infected and Shed PCV2
No effect of parity

9. • Serum and swabs were collected pre-suckling
• 78% of piglets were born viremic
• All PCR-positive samples were PCV2b (n=219)
Serum
Piglets are born Viremic
Skin Swabs

10. PCV2 is present in pre-
suckling piglet serum
• Non-viremic sows on Farms
2, 3, 5, and 6 gave birth to
viremic piglets.
• Sows are PCV2 positive even
in the absence of observable
viremia.
Nonviremic Sows Produce Viremic Piglets
A Negative PCR Test is not Proof of Negative

11. Piglet skin
qPCR Detects Live, Infectious Virus in Pigs and
Environment, Except on Sanitized Surfaces
Piglet serumSow Serum
Crate Bar

12. Serum IgG
• Anti-PCV2 antibodies are present in serum, colostrum, and oral fluids of sows
• Sows from farm 3 and 5 were vaccinated and have universally high antibodies
Colostrum IgG
Sows have High Levels of anti-PCV2 Antibodies

13. PCV2 Infection is Persistent
• Even in the presence of PCV2-specific
antibodies, PCV2 viremia is maintained.
• Once an animal is infected, it is infected for life.
0
20
40
60
80
100
0 5 10 15 20 25
%PCV2positivepigs
Piglet age (weeks)
Viral DNA levels
Sow
Piglets
0
1
2
3
0 5 10 15 20 25
AverageODvalue
Piglet age (weeks)
IgG Antibody levels
Sow
Piglets

14. Persistent infection: Vaccination Evidence
Young pigs
(45 kg)
Old pigs
(100 kg)
January neg* neg
March neg neg
May 104 107
June neg neg
August neg neg
October neg neg
November neg neg
January neg neg
One batch
not vaccinated
Vaccination can suppress viremia to non-detectable levels.
However, virus reappeared when vaccination was stopped.
Vaccination does not cure infection.

15. • The farrowing environment is thoroughly contaminated
with PCV2.
• Growing piglets are under constant viral challenge from the
environment and from the sow.
• Piglets can be infected with PCV2 in utero, during birth, and
from the environment.
virus
Maternal Ab
piglet
antibodies
10-15 weeks
Pigs are Infected at Birth - Infection can be Lifelong

16. Six Years Later: What is the PCV2 Status
A B AB A B AB
102
103
104
105
106
107
108
109
1010
Viralcopies/ml
2006 2012
Viral loads are reduced.

17. 0
10
20
30
40
50
60
70
80
90
Positive Negative
%PCV2positivepigs
Large Increase in PCR-negative pigs
2006
2012
Change in PCR Status 2006 - 2012

18. a b
c d
Anti-Rep
Anti-Cap
Infected + Vaccinated 81%
Vaccinated Only 13%
Background
noise 3%
Negative 3%
Serological Status of Finishing Pigs - 2012

19. Vaccination Suppresses but does not Cure Infection
Young pigs
(45 kg)
Old pigs
(100 kg)
January neg* neg
March neg neg
May 104 107
June neg neg
August neg neg
October neg neg
November neg neg
January neg neg
One batch
not vaccinated
Vaccination can suppress viremia to non-detectable levels.
However, virus reappeared when vaccination was stopped.

20. Conclusion: PCV2 causes disease, but presence in lymph nodes does not
prevent immune response to PCV2 vaccination.
Kristensen et al. 2011. Prev Vet Med 98:250.
Vaccination Works: Meta-Analysis (66 trials)
Vaccines against PCV2 improve growth Vaccines against PCV2 reduce mortality

21. How is vaccination working????????????
 No one really knows the mechanism.
 Vaccines do not induce robust antibody response.
 Neutralizing antibodies exist but do not eliminate virus.
 Cytotoxic T cells not a general feature of protein vaccines.
 But, no question that it works.

22. Concluding Observations
 PCV2 is a highly conserved virus displaying limited genetic
diversity in the United States
 PCV2 is endemic is swine herds; PCV2b is more common
than PCV2a.
 PCV2 exposure starts at birth; infection can be lifelong.
 Vaccination effectively controls PCVAD and reduces
infectious pressure, but does not eliminate virus.