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Airborne Transmission of Highly Pathogenic Avian Influenza Virus
Carmen Alonso, Montserrat Torremorell, Peter Raynor, Peter Davies
Allen D. Leman ConferenceSeptember 21st 2015
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
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
HPAI
• Lethal in poultry: severe disease and sudden onset
• Highly contagious• Internal
hemorrhaging in 48h • Mortality
approaches 100%www. cnews.com
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)
www.aphis.usda.gov
Pacific Flyway
Central/ Mississippi Flyway
MN 105 cases
IA 75 cases
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
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
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
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
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
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
Cyclonic air collector (Midwest Micro-Tek)
200-400 l/min
Corzo et al, 2012
Air Samplers
Andersen Cascade Impactor28.3 l/min
Tish Cascade Impactor 1,1000 l/min
Andersen Cascade Impactor (ACI)
28.3 l/min8 stages 0.01 – 10µm 60 minutes
Tish Cascade Impactor (TSI) 1,100 l/min5 stages 0.01 – 10µm 30 minutes
Turkey flock sampling
Turkey flock sampling
Layer flocks
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).
Diagnostic testing
• RT-PCR: UMN VDL– Ct values < 35 positive, 35-40 suspect, and >40
negative• Virus isolation: NVSL and UMN VDL
Results
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 – 35Positive Ct values layers: 26 - 32
Sampling events by distance (RT-PCRs)
Inside 5 m 70-150 m 500-1000 m
TurkeysPositive 14 (52%) 7 (50%) 0 (0%) NTSuspect 6 (22%) 7 (50%) 6 (67%) NTNegative 7 (26%) 0 (0%) 3 (33%) NT
LayersPositive 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%)
TotalPositive 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%)
HPAI particle size distribution(ACI Layers)
HPAI particle size distribution (ACI Turkeys)
Summary of RT-PCR results from surfaces
Layer 1* Layer 2 Total Range Ct values
Positive 0 (0%) 7 (63%) 7 (35%) 29.03-32.15Suspect 4 (45%) 4 (36%) 8 (40%) 35.14-39.15Negative 5 (55%) 0 (0%) 5 (25%) >40
Total 9 (100%) 11 (100%) 20 (100%)
* Layer barn in process of depop
Virus isolation from air samples results
Particles > 2.1 µm
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
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.
Acknowledgements
Brian McCluskey, USDA/APHISMia Torchetti, NVSLDevi Patnayak, UMN VDLRobert Porter, UMN VDL University of MN Public Health Residents and
Swine graduate students Poultry industry veterinarians and poultry producers
Thank you!