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!

alons015@umn.edu