Dynamics of influenza A infection 
in a wean to finish population
Andres Diaz, Cesar Corzo,
Marie Culhane, Montserrat Tor...
Outline
• Introduction
– Influenza A virus (IAV) and swine populations

•
•
•
•
•

Objectives
Materials and methods
Result...
Introduction
•
•
•
•
•
•

Enveloped virus
ss -sense RNA Virus
8 Gene segments
12 different proteins
Hemagglutinin (HA) - 1...
IAV Diversity – Antigenic drift

Plos Pathogens 2011;7(6):e1002077
IAV Diversity – Antigenic shift

Advances in virus research 2008;72:127-154
IAV and swine population
• Worldwide distributed
• Endemic or epidemic?
• Primary cause of disease in pigs
– Respiratory d...
IAV diversity in growing pigs 

Emerging infectious diseases 2013;19(6):954-960
IAV Transmission in pigs
•
•
•
•

Direct contact
Airborne transmitted
Fomites
Transmission rate (R0)
– Active immunity
• I...
Research questions
• How is IAV maintained in swine populations and
what is the role of weaned pigs in this process?
• Wha...
Objectives
• To characterize the evolution of IAV infection
and transmission in weaned pigs
– To explore IAV transmission ...
Materials and methods
•

Cohort study: Prospective over time

•

1 endemically infected wean to finishing farm
–
–
–

•

M...
0 1 2 3

4 5 6 7 8 9 10 11 12 13 14 15

Nasal swab

X X X X

X X X X X X X

X

X

X

X

X

Oral fluid

X X X X

X X X X X ...
Laboratory tests
• RT-PCR (M gene): Nasal swabs and oral
fluids
– Positive CT < 34
– Suspect > 34 < 40
– Negative > 40

• ...
Analysis and hypothesis testing
• Seroprevalence
– Mean change of the S/N value over time (paired t-test,
p<0.05 between w...
Results
Serology
0 vs 4
0 vs 8
0 vs 12
4 vs 8
4 vs 12
8 vs 12

p<0.05
p<0.05
p<0.05
p<0.05
p<0.05
p<0.05
PW4 vs SW4
PW4 vs NW4
PW8 vs SW8
PW8 vs NW8
PW12 vs SW12
PW12 vs NW12

p<0.05
p>0.05
p>0.05
p>0.05
p>0.05
p>0.05

SW4 vs N...
Results
RT-PCR
Positives

Re infected

99 (75%)

29 (29%)

Positives

Re infected

124 (98%)

102 (82%)
Epidemiological findings
Week

Prevalence rate%

Incidence rate %

Cumulative Incidence rate

R

0

19

NA

1

50

45

45
...
Work in progress....
• 96 samples selected for whole genome
amplification and sequencing (Antigenic drift and
shift)
• Sel...
Conclusions
• Wean pigs can be a source of IAV to other
swine populations
• The presence of maternal immunity in
weaned pi...
Conclusions
• Maternal immunity at weaning was correlated with antibody
levels at 4 weeks post weaning but not at 8 and 12...
Acknowledgments
•
•
•
•
•
•
•
•

Dr. Montse Torremorell
Dr. Srinand Sreevatsan
Dr. Marie Gramer
Dr. Cesar Corzo
Dr. HanSoo...
Andres Diaz - Dynamics of swine influenza in a wean-finish population
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Andres Diaz - Dynamics of swine influenza in a wean-finish population

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Dynamics of swine influenza in a wean-finish population - Andres Diaz, University of Minnesota, College of Veterinary Medicine, from the 2013 Allen D. Leman Swine Conference, September 14-17, 2013, St. Paul, Minnesota, USA.

More presentations at http://www.swinecast.com/2013-leman-swine-conference-material

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  • Any other authors that I should include?
  • Cesar’s work
  • Transmission routes and transmission rates estimates
  • Red ones are positive at weaning, grays are negative
  • PW=Positive at weaning, SW=Suspect at weaning, NW=Negative at weaning. Numbers indicate the week sampled
  • Two epidemic waves
  • Andres Diaz - Dynamics of swine influenza in a wean-finish population

    1. 1.  Dynamics of influenza A infection  in a wean to finish population Andres Diaz, Cesar Corzo, Marie Culhane, Montserrat Torremorell Allen D. Leman Swine Conference 2013 Saint Paul, September 17th 2013
    2. 2. Outline • Introduction – Influenza A virus (IAV) and swine populations • • • • • Objectives Materials and methods Results Work in progress Conclusions
    3. 3. Introduction • • • • • • Enveloped virus ss -sense RNA Virus 8 Gene segments 12 different proteins Hemagglutinin (HA) - 17 subtypes Neuraminidase (NA) - 9 subtypes Cell Host & Microbe 2012;7(6):440-451
    4. 4. IAV Diversity – Antigenic drift Plos Pathogens 2011;7(6):e1002077
    5. 5. IAV Diversity – Antigenic shift Advances in virus research 2008;72:127-154
    6. 6. IAV and swine population • Worldwide distributed • Endemic or epidemic? • Primary cause of disease in pigs – Respiratory disease complex – Reduced feed conversion and ADG – Increased number of days to market • Public health threat Veterinary research 2007;38(2):243-260 Cell Host & Microbe 2012;7(6):440-451
    7. 7. IAV diversity in growing pigs  Emerging infectious diseases 2013;19(6):954-960
    8. 8. IAV Transmission in pigs • • • • Direct contact Airborne transmitted Fomites Transmission rate (R0) – Active immunity • Immune pigs (homologous virus) • Immune pigs (heterologous virus) • Naïve pigs 0 1 10.66 (95% CI 0.39, 2.09) (95% CI 6.57, 16.46) 0.8 7.1 10.4 (95% CI 0.1, 3.7) (95% CI 4.2, 11.3) (95% CI 6.6, 15.8) – Passive immunity • Immune pigs (homologous virus): • Immune pigs (heterologous virus) • Naïve pigs Veterinary research 2011;42(1):120 Vaccine 2013;31(3):500-505 Transboundry and emrging diseases 2012;59(SI:1):68-84
    9. 9. Research questions • How is IAV maintained in swine populations and what is the role of weaned pigs in this process? • What is the transmission and infection pattern of IAV in weaned populations? • How does IAV change over time in endemically infected populations?
    10. 10. Objectives • To characterize the evolution of IAV infection and transmission in weaned pigs – To explore IAV transmission pattern in weaned pigs – To understand the association between IAV exposure, immunity and infection after weaning
    11. 11. Materials and methods • Cohort study: Prospective over time • 1 endemically infected wean to finishing farm – – – • MN 8 barns ≈ 2000 pigs per barn Single source of pigs – Sow herd positive • 132 pigs randomly selected from 2000 pigs weaned – 95% confident to detect at least 1 when the prevalence is higher than 2.5% • Ear tagged and identified at arrival
    12. 12. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Nasal swab X X X X X X X X X X X X X X X X Oral fluid X X X X X X X X X X X X X X X X Serum sample X X X X
    13. 13. Laboratory tests • RT-PCR (M gene): Nasal swabs and oral fluids – Positive CT < 34 – Suspect > 34 < 40 – Negative > 40 • ELISA S/N (NP protein): Serum samples – Positive SN < 0.6 – Suspect SN > 0.6 < 0.9 – Negative > 0.9
    14. 14. Analysis and hypothesis testing • Seroprevalence – Mean change of the S/N value over time (paired t-test, p<0.05 between weeks) – Effect of being seropositive at weaning on the seroprevalence after weaning (paired t-test, p<0.05) • Weekly prevalence – Number of positive cases by week – Comparison of the number of positives over time (chi square test, p<0.05) • Weekly incidence – Number of NEW cases by week • Assessing re-infection with IAV
    15. 15. Results Serology
    16. 16. 0 vs 4 0 vs 8 0 vs 12 4 vs 8 4 vs 12 8 vs 12 p<0.05 p<0.05 p<0.05 p<0.05 p<0.05 p<0.05
    17. 17. PW4 vs SW4 PW4 vs NW4 PW8 vs SW8 PW8 vs NW8 PW12 vs SW12 PW12 vs NW12 p<0.05 p>0.05 p>0.05 p>0.05 p>0.05 p>0.05 SW4 vs NW4 SW8 vs NW8 SW12 vs NW12 p<0.05 p>0.05 p>0.05
    18. 18. Results RT-PCR
    19. 19. Positives Re infected 99 (75%) 29 (29%) Positives Re infected 124 (98%) 102 (82%)
    20. 20. Epidemiological findings Week Prevalence rate% Incidence rate % Cumulative Incidence rate R 0 19 NA 1 50 45 45 1.6 2 64 52 97 1.2 3 10 5 102 4 4 3 105 5 4 3 108 6 15 5 113 7 55 50 163 8 29 6 169 9 5 3 172 10 3 3 175 11 2 1 176 12 4 4 180 13 4 4 184 14 4 4 188 15 6 6 194 -
    21. 21. Work in progress.... • 96 samples selected for whole genome amplification and sequencing (Antigenic drift and shift) • Selection of samples for VI – Reference virus by week • Estimate real exposure by HI reactivity of serum samples to references viruses and explore antigenic differences by antigenic cartography
    22. 22. Conclusions • Wean pigs can be a source of IAV to other swine populations • The presence of maternal immunity in weaned pigs is highly variable • The maternal immunity did not protect weaned pigs from IAV infection but it did reduce transmission (lower R0).
    23. 23. Conclusions • Maternal immunity at weaning was correlated with antibody levels at 4 weeks post weaning but not at 8 and 12 weeks post weaning. • The interaction between IAV transmission, infection, and maternal immunity allowed for two epidemic waves of IAV in less than 8 weeks post-weaning • Our results indicate that pigs can be re-infected over a short period of time and as a result IAV can remain in the population. • At the end of the study, all pigs tested positive to IAV by ELISA, indicating that all pigs were infected to the IAV.
    24. 24. Acknowledgments • • • • • • • • Dr. Montse Torremorell Dr. Srinand Sreevatsan Dr. Marie Gramer Dr. Cesar Corzo Dr. HanSoo Joo Dr. Meggan Craft Pipestone Veterinary clinic – Dr. Spencer Wayne Swine producers and farm staff • Graduate students and research assistants – Victor Neira – Macarena Cortez – My Yang – Mathew Allerson – Steve Tousignant – Carmen Alonso – Nubia Macedo – Maria Jose Clavijo – Jonathan Ertl – Jennifer Reynolds – Douglas Marthaler
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