Airborne Transmission Of Highly Pathogenic Avian Influenza (HPAI) And Lessons For Pigs - Dr. Carmen Alonso, from the 2015 Allen D. Leman Swine Conference, September 19-22, 2015, St. Paul, Minnesota, USA. More presentations at http://www.swinecast.com/2015-leman-swine-conference-material

1. Airborne Transmission of Highly
Pathogenic Avian Influenza Virus
Carmen Alonso, Montserrat Torremorell,
Peter Raynor, Peter Davies
Allen D. Leman Conference
September 21st
2015

2. Avian influenza
• Avian influenza Type A virus (H5 and H7)
• Subdivided into 2 groups (Chicken %M in lab.
conditions):
– Low pathogenic avian influenza (LPAI)
– Highly pathogenic avian influenza (HPAI)
• Natural reservoir  Wild aquatic birds
(asymptomatic)
• Shed in saliva, nasal
secretions and feces

3. Avian influenza
• Potential for LPAI to evolve into HPAI viruses (H5,
H7)
• Potential for rapid spread and significant illness and
death among poultry due to HPAI
• Economic impact and trade restrictions from HPAI
outbreaks
• Possibility of HPAI transmission to humans and pigs

4. HPAI
• Lethal in poultry:
severe disease and
sudden onset
• Highly contagious
• Internal
hemorrhaging in 48h
• Mortality
approaches 100%
www. cnews.com

5. HPAI Outbreak in USA
• First detected in a backyard production in Dec’14
(Oregon)
• H5 HPAI virus in commercial birds detected in MN in
March’15
• Reported in 21 states (15 states with domestic birds
and 6 with wild birds only)

6. www.aphis.usda.gov
Pacific Flyway
Central/
Mississippi Flyway
MN 105
cases
IA 75
cases

7. Airborne Transmission
• Field observations of rapid spread of HPAI cases in
Minnesota in April suggested potential spread via air
• Airborne viruses travel associated with particles of
different sizes and composition
• Particle composition:
– Respiratory secretions
– Fecal material
– Bedding
– Feed dust, etc
www.wattagnet.com

8. Airborne transmission
• Particle size determines:
– Time virus stays suspended in air
– Distance virus travels
– Body site deposition (upper or lower respiratory track, etc)
– Survivability and infectivity of the virus
– Approaches to biosecurity methods (particle size
dependent)
• Our group is experienced in airborne investigations of
swine viruses: PRRSV, influenza and porcine
epidemic diarrhea
• USDA/APHIS approached our group to assist in
airborne investigations in the field

9. HPAI in swine
• Pigs susceptible to intranasal infections with both
mammalian and avian viruses
• “Mixing vessel” Emergence of novel reassortant
viruses
• Swine infection from recombinant H1N1 + HPAI
H5N1 demonstrated experimentally
• Absence of clinical signs and lack of virus in NS
limited use of passive surveillance for disease control
• Risk of pig exposure to avian viruses
in swine dense areas
near poultry operations

10. Objective
• To evaluate the potential for airborne transmission
of highly pathogenic avian influenza (HPAI) virus
in turkey and layer flocks:
– To detect and assess the viability of HPAI virus in air
samples
– To assess airborne particle deposition in surfaces
– To identify the particle size distribution of HPAI virus

11. Material and methods
Flock selection:
•Six flocks with confirmed H5N2 infections
– 3 turkey flocks (MN) and 3 layer flocks (IA, NE)
•Sampling within 3 to 10 days after diagnostic
confirmation
•Mortality rates between 5 and 80% at the time of
sampling, and one flock had already disposed of
a large proportion of dead birds

12. Air Sampling Procedures
• Air sampling locations:
– Inside
– Outside: 5 m, 70-150 m, 500-1000 m (aprox)
• Air samplers:
– Air cyclonic (Midwest Micro-Tek)
– Anderson Cascade Impactor (ACI)
– Tish Cascade Impactor (TSI)
• Total particles: Optical particle counter
Particle sizing

13. Cyclonic air collector
(Midwest Micro-Tek)
200-400 l/min
Corzo et al, 2012
Air Samplers
Andersen
Cascade
Impactor
28.3 l/min
Tish Cascade
Impactor 1,1000 l/min

14. Andersen Cascade Impactor (ACI)
28.3 l/min
8 stages
0.01 – 10µm
60 minutes

15. Tish Cascade Impactor (TSI)
1,100 l/min
5 stages
0.01 – 10µm
30 minutes

16. Turkey flock sampling

17. Turkey flock sampling

18. Layer flocks

22. Airborne particles deposition
• Environmental samples from surfaces in
locations at high risk of direct exposure to the
air exhausted from layer flocks.
• Disposable gloves with gauzes dipped into
sterile media.
• Surfaces:
– Farm fixtures (e.g., silos, walls, fans, door handles)
– Temporary fomites exposed to exhaust air for
approximately 2 hours (e.g., sampling equipment,
plastic containers).

23. Diagnostic testing
• RT-PCR: UMN VDL
– Ct values < 35 positive, 35-40 suspect, and >40
negative
• Virus isolation: NVSL and UMN VDL

24. Results

25. Air sampling events (RT-PCRs)
• 5 out of 6 flocks had positive air samples
Turkeys Layers Total
Positive 21 (42%) 24 (27%) 45 (33%)
Suspect 19 (38%) 17 (19%) 36 (26%)
Negative 10 (20%) 47 (54%) 57 (41%)
Total 50 (100%) 88 (100%) 138 (100%)
Positive Ct values turkeys: 31 – 35
Positive Ct values layers: 26 - 32

26. Sampling events by distance
(RT-PCRs)
Inside 5 m 70-150 m 500-1000 m
Turkeys
Positive 14 (52%) 7 (50%) 0 (0%) NT
Suspect 6 (22%) 7 (50%) 6 (67%) NT
Negative 7 (26%) 0 (0%) 3 (33%) NT
Layers
Positive 12 (100%) 11 (42%) 1 (5%) 0 (0%)
Suspect 0 (0%) 5 (19%) 6 (30%) 6 (20%)
Negative 0 (0%) 10 (38%) 13 (65%) 24 (80%)
Total
Positive 26 (67%) 18 (45%) 1 (4%) 0 (0%)
Suspect 6 (15%) 12 (30%) 12 (41%) 6 (20%)
Negative 7 (18%) 10 (25%) 16 (55%) 24 (80%)
Total 39 (100%) 40 (100%) 29 (100%) 30 (100%)

27. HPAI particle size distribution
(ACI Layers)

28. HPAI particle size distribution
(ACI Turkeys)

29. Summary of RT-PCR results
from surfaces
Layer 1* Layer 2 Total Range Ct
values
Positive 0 (0%) 7 (63%) 7 (35%) 29.03-32.15
Suspect 4 (45%) 4 (36%) 8 (40%) 35.14-39.15
Negative 5 (55%) 0 (0%) 5 (25%) >40
Total 9 (100%) 11 (100%) 20 (100%)
* Layer barn in process of depop

30. Virus isolation from air samples
results
Particles > 2.1 µm

31. Conclusions
• HPAI can be aerosolized from infected flocks and
remain airborne
• HPAI RNA was detected in air samples collected
inside and immediately outside of the infected
premises. Low levels of genetic material were
detected at distances of 70 to 1000 m
approximately.
• Viable virus detected from air up to 70 m from an
infected facility and in particles >2.1 microns

32. Conclusions
• Considerable surface environmental contamination
was demonstrated and widespread across multiple
surfaces outside a layer flock
• HPAI was associated to multiple size particles
• Both, the transport of airborne particles and the
deposition of infectious airborne particles on the
surfaces around infected premises appear to be
risk for the spread of HPAI to other locations.

33. Acknowledgements
Brian McCluskey, USDA/APHIS
Mia Torchetti, NVSL
Devi Patnayak, UMN VDL
Robert Porter, UMN VDL
University of MN Public Health Residents and
Swine graduate students
Poultry industry veterinarians and poultry
producers

34. Thank you!
alons015@umn.edu