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Airborne Influenza A Is Detected in the Personal Breathing Zone of Swine Veterinarians

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The 2009 H1N1 pandemic emphasized a need to evaluate zoonotic transmission of influenza A in swine production. Airborne influenza A virus has been detected in swine facilities during an outbreak. However, the personal exposure of veterinarians treating infected swine has not been characterized. Two personal bioaerosol samplers, the NIOSH bioaerosol sampler and the personal high-flow inhalable sampler head (PHISH), were placed in the breathing zone of veterinarians treating swine infected with either H1N1 or H3N2 influenza A. A greater number of viral particles were recovered from the NIOSH bioaerosol sampler (2094 RNA copies/m3) compared to the PHISH sampler (545 RNA copies/m3). In addition, the majority of viral particles were detected by the NIOSH bioaerosol sampler in the >4 μm size fraction. These results suggest that airborne influenza A virus is present in the breathing zone of veterinarians treating swine, and the aerosol route of zoonotic transmission of influenza virus should be further evaluated among agricultural workers.
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RESEARCH ARTICLE
Airborne Influenza A Is Detected in the
Personal Breathing Zone of Swine
Veterinarians
Kate M. OBrien, Matthew W. Nonnenmann*
Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa
City, Iowa, United States of America
*matthew-nonnenmann@uiowa.edu
Abstract
The 2009 H1N1 pandemic emphasized a need to evaluate zoonotic transmission of influ-
enza A in swine production. Airborne influenza A virus has been detected in swine facilities
during an outbreak. However, the personal exposure of veterinarians treating infected
swine has not been characterized. Two personal bioaerosol samplers, the NIOSH bioaero-
sol sampler and the personal high-flow inhalable sampler head (PHISH), were placed in the
breathing zone of veterinarians treating swine infected with either H1N1 or H3N2 influenza
A. A greater number of viral particles were recovered from the NIOSH bioaerosol sampler
(2094 RNA copies/m
3
) compared to the PHISH sampler (545 RNA copies/m
3
). In addition,
the majority of viral particles were detected by the NIOSH bioaerosol sampler in the >4μm
size fraction. These results suggest that airborne influenza A virus is present in the breath-
ing zone of veterinarians treating swine, and the aerosol route of zoonotic transmission of
influenza virus should be further evaluated among agricultural workers.
Introduction
The emergence of the swine-origin H1N1pdm09 influenza A outbreak illustrated the need to
understand the processes underlying the antigenic shift and zoonotic transmission of influenza
A. Influenza A is a highly contagious respiratory virus with 3,000 to 49,000 deaths, annually.
[1,2] The expression of the glycoproteins, hemagglutinin (HA) and neuraminidase (NA), on
the viral envelope determines the species specific infection via the sialic acid linked oligosac-
charide receptors.[3,4] However, some influenza A variants cross the species barrier.[57] Por-
cine respiratory epithelium express both human and avian specific sialyl-oligosaccharide
receptors.[8] Upon the co-infection of human and avian influenza, the reassortment of influ-
enza A viral genome can occur in porcine epithelium and lead to formation of novel variants.
[9,10] For example, phylogenetic analysis of circulating influenza A virus among American
and Italian swine herds in the 1990s showed that the virus was a reassortment of avian, human,
and classic swine viral genome.[11,12] Furthermore, the genome sequencing of H1N1pdm09
influenza A showed that the viral genome was derived from classical swine lineage, Eurasian
PLOS ONE | DOI:10.1371/journal.pone.0149083 February 11, 2016 1/8
OPEN ACCESS
Citation: OBrien KM, Nonnenmann MW (2016)
Airborne Influenza A Is Detected in the Personal
Breathing Zone of Swine Veterinarians. PLoS ONE
11(2): e0149083. doi:10.1371/journal.pone.0149083
Editor: Hui-Ling Yen, The University of Hong Kong,
HONG KONG
Received: October 7, 2015
Accepted: January 26, 2016
Published: February 11, 2016
Copyright: © 2016 OBrien, Nonnenmann. This is an
open access article distributed under the terms of the
Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any
medium, provided the original author and source are
credited.
Data Availability Statement: All relevant data are
within the paper.
Funding: The research was funded by the University
of Iowa College of Public Health New Investigator
Award-MWN. The funder has no role in study design,
data collection and analysis, decision to publish, or
preparation of the manuscript.
Competing Interests: The authors have declared
that no competing interests exist.
avian-like lineage, and North American triple reassortment lineage.[6,13] Clearly, reassortment
of the influenza virus genome occurs in production animal populations. This reassortment
places both human and animal populations at risk for the emergence of a highly pathogenic
strain of influenza, as is currently ongoing in the poultry industry with the H5N2 outbreak.
[14,15] Therefore, determining routes of zoonotic transmission is critical for the prevention of
influenza virus transmission.
Swine influenza is endemic throughout the United States and causes a high morbidity rate
among swine herds.[16] At the present time, the influenza A subtypes (H1N1, H3N2, and
H1N2) are the most common infection circulating in swine.[16] The zoonotic transmission of
swine influenza can occur via the direct, indirect, or airborne route. The direct and indirect
route has been well documented, but the airborne route of influenza A infection is not well
understood.[17] Corzo et al demonstrated that airborne influenza A particles at a concentra-
tion of 3.20X10
5
RNA copies/m
3
and 8.58X10
3
RNA copies/m
3
can be detected inside the
swine facilities and at most 2.1 km downwind of an infected swine herd.[18] Furthermore,
aerosolized influenza A virus detection was dependent upon viral shedding in the swine herds
nasal secretion and density of swine infected.[19] However, these studies collected area air sam-
ples from one central location, and did not measure aerosols in swine veterinarianspersonal
breathing zone.[18,19] Therefore, the personal inhalation exposure of influenza A virus among
swine veterinarians needs to be characterized.
Swine workers and their families have a significantly higher risk of influenza A infection
than their non-exposed neighbors.[20] Also, swine workers have elevated antibody titers
against circulating swine influenza virus variants and higher prevalence of seroconversion than
the local communities.[20,21] The protection of agricultural workers and swine from zoonotic
transmission of influenza A virus is relevant to both public health and the swine production
industry.
The aim of this study was to determine the concentration of influenza A virus in the per-
sonal breathing zone of personnel working with infected swine herds.
Methods
Sample Population
Two swine veterinarians (veterinarian 1:Farms 12 and veterinarian 2:Farms 35) were
recruited for this study. The veterinarians treated infected swine herds on private farms
throughout the State of Iowa. Due to confidentiality, the specific geographical location of the
private farms in the State of Iowa cannot be disclosed. Swine veterinarians were called to a swine
farm when there was a suspected influenza A infection among the herd. The swine veterinarian
took either oral or nasopharyngeal fluid samples. Once a swine herd tested positive for influenza
A virus, the veterinarian contacted the research team. This study was carried out with approval
from the University of Iowa Institutional Review Board in the Human Subjects Office. Written
consent was received from all swine veterinarians that participated in the study.
Personal sampling of aerosolized influenza A
Study participants were equipped with a backpack containing two aerosol samplers, the
National Institute of Occupational and Safety Health (NIOSH) bioaerosol sampler BC251
(NIOSH; Atlanta, GA) and the personal high-flow inhalable sampler head (PHISH),[22,23]
and two air pumps, AirChek XR5000 (SKC Inc.; Eighty Four, PA) and Omni (BGI; Waltham,
MA). The NIOSH bioaerosol sampler and PHISH were calibrated to an air flow rate of 3.5 L/
min and 10 L/min, respectively. The NIOSH bioaerosol sampler contained a 15 mL conical
tube (Fisher Scientific; Pittsburgh, PA), a 1.5 mL microcentrifuge tube (Fisher Scientific;
Characterization of Airborne Swine Influenza
PLOS ONE | DOI:10.1371/journal.pone.0149083 February 11, 2016 2/8
Pittsburgh, PA), and a 37-mm, 0.3 μm pore size polytetrafluoroethylene (PTFE) filter (SKC
Inc.; Eighty Four, PA). The PHISH is a newly designed sampler that uses standard 37 mm filter
material to collect aerosols in the breathing zone that are representative of the inhalable size
fraction (d
50
= 100 μm) at a flow rate greater than other inhalable samplers. For this experi-
ment, the PHISH used a 37-mm, 0.3 μm pore size PTFE filter, which has been recommended
for virus aerosol sampling. The NIOSH and PHISH were placed on the study participants
lapels. During sampling, study participants performed their tasks which included collecting
swine oral or nasopharyngeal samples, walking up and down each pen, and observing the
behavior of the swine. One integer aerosol sample was collected per bioaerosol sampler per
farm. Typically, 3060 minutes were required to accomplish the oral fluid collection and obser-
vation tasks.
Extraction of influenza virus from sampling media
Hanks Balanced Salt Solution (HBSS) (Gibco; Waltham, MA) was added to the PTFE filters (5
ml), 15 ml tube (5 ml) and 1.5 ml conical tube (1.5 ml) and vortexed for five minutes at a low
speed. Samples were aliquoted and stored at -80°C.
Collection of swine oral or nasopharyngeal samples
Due to the time difference between the initial evaluation of an infected swine herd and sam-
pling time, the swine veterinarian collected either an oral or nasopharyngeal sample to confirm
the presence of influenza A virus infection among the swine herd during sampling. For an oral
sample, a cotton rope was hung in the pen. The pigs were allowed to chew on the rope for
approximately 30 minutes. The rope was placed in a plastic bag and squeezed to discharge the
oral fluids. The oral fluids were then poured into a 50 mL conical tube (Fisher Scientific; Pitts-
burgh, PA) and placed on ice. For nasopharyngeal samples, the veterinarian placed a flock
swab (BD; Sparks, MD) into the nasopharynx and rotated the swab twice. The flock swab was
placed into 3 mL of universal viral transport media (BD; Sparks, MD) and placed on ice. Both
oral and nasopharyngeal samples were aliquoted and stored at -80°C for further analysis. The
criteria for swine to test positive for influenza A virus was a reverse transcriptase real time
quantitative polymerase chain reaction (qPCR) Ct value 37 for the oral or nasopharyngeal
swab sample.
Viral RNA isolation and Quantitative Real-time Polymerase Chain
Reaction
Viral RNA was extracted from 1 mL of collected oral, nasal, or aerosol samples using the
QIAamp Viral RNA Mini kit (Qiagen; Valencia, CA) per manufacturers instructions. Viral
RNA was reverse transcribed into complimentary DNA using the SuperScript
1
Platinum One
Step qRT-PCR kit (Life Technologies; Waltham, MA) for a final volume of 25 μL. A 1:4 serial
dilution standard curve was generated using influenza A plasmid DNA (Attostar LLC;
St. Louis, MN) for qRT-PCR. All samples were run in triplicates. Influenza A primer and probe
sequences are as follows: Forward: 5- GCA CGG TCA GCA CTT ATY CTR AG-3Reverse:
5-GTG RGC TGG GTT TTC ATT TGG TC-3and probe: 6FAM-CA GAA TAT ACA TCC
RGT CAC AAT TGG ARA A-BHQ1.[24] Real-time qPCR was performed using TaqMan
reagents (Life Technologies; Waltham, MA) on a QuantStudio 7 Flex (Life Technologies; Wal-
tham, MA) system using the protocol: 50°C for 30 minutes, 95°C for 10 minutes, 45 cycles of
95°C for 15 seconds followed by 55°C for 35 seconds.
Characterization of Airborne Swine Influenza
PLOS ONE | DOI:10.1371/journal.pone.0149083 February 11, 2016 3/8
Data analysis
RNA copies were calculated from the samplesCt values utilizing the linear regression equation
generated from the influenza A plasmid DNA standards. RNA copies per ml were multiplied
by the wash volume (1.5 ml or 5 ml) and divided by the total volume of air collected during
sampling. The data are reported as geometric mean ± geometric standard deviation. The fol-
lowing equations are examples of the calculations used:
Log Viral RNA copiesðÞ¼
CtðsampleÞðyinterceptÞ
slope
Viral RNA copies=m3¼Viral RNA copies
Volume of air sampled
Results
Inhalation exposure to influenza virus aerosol
At the time of sampling, the swine veterinarian took either nasopharyngeal or oral samples to
verify the presence of influenza A infection among the swine herd. Oral and nasal samples
were collected from either swine pens or individual swine that presented with influenza-like
symptoms. Oral samples indicate a positive pen containing at most 30 pigs; whereas, a naso-
pharyngeal swab was collected from individual pigs. Farms 14 had at least one oral and nasal
sample with a Ct value below the required 37 positive threshold limit; thereby, demonstrating
that the swine production facility had infected swine. 46 and 3065 viral RNA copies/mL were
detected in oral samples collected from the pen. There were 145920 and 463 RNA copies/mL in
nasal swabs collect from individual pigs. Farm 5 did not test positive for influenza A. Three out
of the four farms were infected with H3N2 subtype of influenza A. Three farms had natural
ventilation (side wall curtains closed) (Table 1).
The 15 mL conical tube of the NIOSH bioaerosol sampler (particle size selection of >4μm)
collected the majority of viral RNA copies/m
3
(1743 RNA copies/m
3
). The 1.5 mL microcentri-
fuge tube (14μm) and the PHISH filter collected similar amounts of viral RNA copies/m
3
(232 and 545 RNA copies/m
3
). The NIOSH filter (<1μm) of the NIOSH bioaerosol sampler
collected the lowest number of viral particles per volume of air, and influenza RNA viral parti-
cles were undetectable after one-week post-diagnosis (Table 2). Farm 5 nasal swab did not test
Table 1. Summary of the swine farms during sampling. The criteria for a swine to test positive for influenza A virus was a qPCR Ct value 37 among the
swine oral or nasopharyngeal samples. Data is reported as the average RNA copies/mL of either oral or nasal fluid. All samples were collected during the
peak months of influenza A infections. *Room contained 20 sows with 250 piglets. Natural ventilation is not applicable for the sow/nursery farmbecause the
farm is enclosed with solid walls.
Farm Subtype of
inuenza A
RNA copies/
mL
No. Inuenza A qPCR
Positive/No.Tested
Number of
swine
Type of
farm
Month Outside
temperature
Natural
ventilation
1 H1N1 46 oral 1/3 pen 3000 Nursery November -9°C Curtains
closed
2 H3N2 3065 oral 2/3 pen 2500 Finisher October 13°C Curtains open
3 H3N2 145920 nasal 6/7 swine 270*Sow/
Nursery
April 6°C Not applicable
4 H3N2 463 nasal 2/2 swine 2400 Finisher April 8°C Curtains
closed
5 H1N2 Not detected
nasal
0/1 swine 2400 Nursery April 16°C Curtains
closed
doi:10.1371/journal.pone.0149083.t001
Characterization of Airborne Swine Influenza
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positive for influenza A virus, but 582 and 14 viral RNA copies/m
3
were collected in the
NIOSH 15 mL and 1.5 mL tubes (Table 2). However, only one pig was tested at the time of
sampling (Table 1). Also, viable virus was detected in both the NIOSH bioaerosol sampler and
the PHISH sampler from Farm 3.
Discussion
To determine the personal inhalation exposure to airborne influenza A virus among swine vet-
erinarians, study participants wore two personal bioaerosol samplers. The NIOSH bioaerosol
sampler recovered approximately four times more influenza A RNA viral particles than the
novel PHISH sampler (Table 2). We have previously compared these two bioaerosol samplers
in chamber trials by aerosolizing H1N1 influenza A. Similar to our chamber experiments (data
not shown), NIOSH bioaerosol sampler, with the majority of viral aerosol particles collected in
the 1.5 mL microcentrifuge tube (size particle 14μm), recovered more virus than the PHISH.
Unlike our chamber experiments (data not shown), the 15 mL conical tube of the NIOSH
bioaerosol sampler collected 80% of aerosol influenza A particles in the field (Table 2).
Recently, it has been demonstrated that airborne influenza A RNA viral particles can be
detected in particle size ranges from 0.4 to 10 μm, with the majority of the RNA viral particles
and viable influenza A virus greater than 2.1 μm.[25] This study, along with previous research
suggest that airborne influenza A viruses are present in particle sizes greater than 4 μm. [25]
However, a more in-depth analysis (i.e., electron microscopy) is needed to determine the exact
particle sizes of aerosolized influenza A virus particles in the swine facilities.
Considering influenza A virion size is 80120 nm, these results would suggest that airborne
influenza A is bound to organic dust or other particulate matter in the swine barn.[4] Organic
dust promotes the recruitment of innate immune cells via the upregulation of chemoattractant
cytokines (i.e., interleukin-8 and interleukin-6) in the respiratory tract of both humans and
swine.[2628] The innate immune cells, alveolar macrophages, are critical for the defense
against influenza A infection in the swine respiratory tract.[29] H1N1 infected swine depleted
of alveolar macrophages had a 40% higher mortality rate than controlled infected swine herds.
[29] Interestingly, organic dust reduces macrophage phagocytic activity.[30,31] Thereby, sug-
gesting that organic dust exposure increases the susceptibility of the respiratory tract to viral
infection. Viable avian influenza has been detected in dust and other particulates downwind of
Table 2. Influenza A RNA copies/m
3
of air concentrations detected in the swine facilities using two personal bioaerosol samplers. Personal sam-
ples were collected among veterinarians working in swine production facilities that were infected with influenza A (H1N1 or H3N2) virus. Swine veterinarians
were called to the swine facilities during a suspected influenza A infection and collected bodily fluids for a diagnosis. Samples were collected at various time
during or after this initial evaluation of the infected swine herd. The NIOSH bioaerosol sampler and the PHISH collectedsamples at a flow rate of 3.5 L/min
and 10 L/min, respectively. Total RNA copies/m
3
were determined by qPCR. The summary of the data is reported as geometric mean (GM) and geometric
standard deviation (GSD).
Farm Time elapsed after
initial evaluation
NIOSH 15 mL(>4μm)
(RNA copies/m
3
)
NIOSH 1.5 mL (1
4μm) (RNA copies/m
3
)
NIOSH lter (<1μm)
(RNA copies/m
3
)
NIOSH total
(RNA copies/m
3
)
PHISH lter (RNA
copies/m
3
)
1 0 days 5471 767 70 6309 2481
2 2 days 3491 1478 171 5140 -
3 7 days 3708 1193 Not detected 4901 552
4 14 days 390 35 Not detected 425 119
5*14 days 582 14 Not detected 596 Not detected
GM
(GSD)
1742 (3) 232 (9) 110 (2) 2094 (4) 545 (5)
*RT-qPCR Ct values from all Farm 5 samples were outside the linear range of the calibration curve
doi:10.1371/journal.pone.0149083.t002
Characterization of Airborne Swine Influenza
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an infected barn.[32,33] In addition, air samples from a live animal market in Minnesota have
tested positive for viable influenza A virus in the pens of infected swine.[34] These results
would suggest that swine influenza may be bound to organic dust or other particulate matter
and could be transmitted via aerosol. These findings have implications for infection control
within swine or other animal production buildings. The findings also have implications for
virus transmission to other neighboring animal production buildings, farms, animal produc-
tion workers and the public. For example, a boy that had contact with swine at a live animal
market was infected with influenza A virus that had 99%-100% genomic identity to that of the
virus detected in a swine herd.[34] However, additional data are needed to further characterize
these virus aerosols and to determine if these virus aerosols have the potential to cause
infection.
Swine are considered the mixing vesselof influenza A virus, leading to the introduction of
novel variants into the general populace (e.g., 1918 H1N1 and 2009 H1N1).[35] This study sug-
gests that swine workers are inhaling aerosolized influenza virus during the treatment of
infected swine and may be the first to be exposed to novel influenza variants. Therefore, swine
industry biosecurity practices and the usage of personal protective equipment (PPE) among
swine workers is imperative to reduce the risk of zoonotic transmission. Personal protective
equipment usage, especially gloves, has shown to decrease seroconverison among swine work-
ers.[36] However, PPE usage is not universally standardized across either small or large farms,
and workers may not increase the usage of PPE when they suspect that swine herds are ill. [36]
These results from this study suggest that a properly fitted respirator (e.g., N95) should be
worn as a standard operation procedure for swine workers entering a facility that houses swine
with an ongoing influenza virus infection. Furthermore, PPE is considered the least effective
solution to exposure prevention in the industrial hygiene hierarchy of controls.[37] The devel-
opment of engineering controls (e.g., filtration and ultraviolet light) is a more effective solution
to reduce influenza aerosols in swine production, and it would decrease inhalation exposure of
viral aerosols among swine workers and uninfected animals in swine production.[38] However,
aerosolization of influenza A is not the only route of transmission. Therefore, it is imperative
that good hygiene practices are observed to reduce direct and indirect transmission of influenza
A virus in the swine production facility and the neighboring swine facilities.
Acknowledgments
The authors would like to thank the swine veterinarians, Paul Armbrecht DVM and Michael
Male DVM, who willingly informed the researchers about an infected swine barn and wore the
samplers while performing their work. The authors would also like to thank NIOSH and Wil-
liam Lindsley PhD for the use of the NIOSH bioaerosol sampler BC251, and T. Renée Anthony
PhD, CIH, CSP for the use of the personal high-flow inhalable sampler head (PHISH).
Author Contributions
Conceived and designed the experiments: KMO MWN. Performed the experiments: KMO.
Analyzed the data: KMO MWN. Contributed reagents/materials/analysis tools: KMO MWN.
Wrote the paper: KMO MWN.
References
1. Osterholm MT. Preparing for the next pandemic. N Engl J Med. 2005; 352(18):183942. PMID:
15872196
2. Blachere FM, Lindsley WG, Slaven JE, Green BJ, Anderson SE, Chen BT, et al. Bioaerosol sampling
for the detection of aerosolized influenza virus. Influenza Other Respir Viruses. 2007; 1(3):11320. doi:
10.1111/j.1750-2659.2007.00020.x PMID: 19453416
Characterization of Airborne Swine Influenza
PLOS ONE | DOI:10.1371/journal.pone.0149083 February 11, 2016 6/8
3. Connor RJ, Kawaoka Y, Webster RG, Paulson JC. Receptor specificity in human, avian, and equine
H2 and H3 influenza virus isolates. Virology. 1994; 205(1):1723. PMID: 7975212
4. Lamb RA, Krug RM. Orthomyxoviridae: The viruses and their Replication. In: Knipe DM, Howley PM
editors. Fields Virology fourth edition, Philadelphia: Lippincott; 2001, p. 14871532.
5. Shaw M, Cooper L, Xu X, Thompson W, Krauss S, Guan Y, et al. Molecular changes associated with
the transmission of avian influenza a H5N1 and H9N2 viruses to humans. J Med Virol. 2002; 66
(1):10714. PMID: 11748666
6. Garten RJ, Davis CT, Russell CA, Shu B, Lindstrom S, Balish A, et al. Antigenic and genetic character-
istics of swine-origin 2009 A(H1N1) influenza viruses circulating in humans. Science. 2009; 325
(5937):197201. doi: 10.1126/science.1176225 PMID: 19465683
7. Li KS, Guan Y, Wang J, Smith GJ, Xu KM, Duan L, et al. Genesis of a highly pathogenic and potentially
pandemic H5N1 influenza virus in eastern Asia. Nature. 2004; 430(6996):20913. PMID: 15241415
8. Nelli RK, Kuchipudi SV, White GA, Perez BB, Dunham SP, Chang KC. Comparative distribution of
human and avian type sialic acid influenza receptors in the pig. BMC Vet Res. 2010; 6:4. doi: 10.1186/
1746-6148-6-4 PMID: 20105300
9. Steel J, Lowen AC. Influenza A virus reassortment. Curr Top Microbiol Immunol. 2014; 385:377401.
doi: 10.1007/82_2014_395 PMID: 25007845
10. Tao H, Li L, White MC, Steel J, Lowen AC. Influenza A Virus Coinfection through Transmission Can
Support High Levels of Reassortment. J Virol. 2015; 89(16):845361. doi: 10.1128/JVI.01162-15
PMID: 26041285
11. Castrucci MR, Donatelli I, Sidoli L, Barigazzi G, Kawaoka Y, Webster RG. Genetic reassortment
between avian and human influenza A viruses in Italian pigs. Virology. 1993; 193(1):5036. PMID:
8438586
12. Zhou NN, Senne DA, Landgraf JS, Swenson SL, Erickson G, Rossow K, et al. Genetic reassortment of
avian, swine, and human influenza A viruses in American pigs. J Virol. 1999; 73(10):88516. PMID:
10482643
13. Smith GJ, Vijaykrishna D, Bahl J, Lycett SJ, Worobey M, Pybus OG, et al. Origins and evolutionary
genomics of the 2009 swine-origin H1N1 influenza A epidemic. Nature. 2009; 459(7250):11225. doi:
10.1038/nature08182 PMID: 19516283
14. Pasick J, Berhane Y, Joseph T, Bowes V, Hisanaga T, Handel K, et al. Reassortant highly pathogenic
influenza A H5N2 virus containing gene segments related to Eurasian H5N8 in British Columbia, Can-
ada, 2014. Sci Rep. 2015; 5:9484. doi: 10.1038/srep09484 PMID: 25804829
15. Clifford J. Highly Pathogenic Avian Influenza: The Impact on the U.S. Poultry Sector and Protecting U.
S. Poultry Flocks: Hearing before the Committee on Agriculture, Nutrition and Forestry, Senate, 114th
Cong. 2015.
16. Vincent AL, Ma W, Lager KM, Janke BH, Richt JA. Swine influenza viruses: a North American perspec-
tive. Adv Virus Res. 2008; 72:12754. doi: 10.1016/S0065-3527(08)00403-X PMID: 19081490
17. Brankston G, Gitterman L, Hirji Z, Lemieux C, Gardam M. Transmission of influenza A in human beings.
Lancet Infect Dis. 2007; 7(4):25765. PMID: 17376383
18. Corzo CA, Culhane M, Dee S, Morrison RB, Torremorell M. Airborne detection and quantification of
swine influenza a virus in air samples collected inside, outside and downwind from swine barns. PLoS
One. 2013; 8(8):e71444. doi: 10.1371/journal.pone.0071444 PMID: 23951164
19. Corzo CA, Romagosa A, Dee SA, Gramer MR, Morrison RB, Torremorell M. Relationship between air-
borne detection of influenza A virus and the number of infected pigs. Vet J. 2013; 196(2):1715. doi: 10.
1016/j.tvjl.2012.09.024 PMID: 23164957
20. Gray GC, McCarthy T, Capuano AW, Setterquist SF, Olsen CW, Alavanja MC. Swine workers and
swine influenza virus infections. Emerg Infect Dis. 2007; 13(12):18718. doi: 10.3201/eid1312.061323
PMID: 18258038
21. Myers KP, Olsen CW, Setterquist SF, Capuano AW, Donham KJ, Thacker EL, et al. Are swine workers
in the United States at increased risk of infection with zoonotic influenza virus? Clin Infect Dis. 2006; 42
(1):1420. PMID: 16323086
22. Koehler KA, Anthony TR, Van Dyke M, Volckens J. Solid versus liquid particle sampling efficiency of
three personal aerosol samplers when facing the wind. Ann Occup Hyg. 2012; 56(2):194206. doi: 10.
1093/annhyg/mer077 PMID: 21965462
23. Anthony TR, Landazuri AC, Van Dyke M, Volckens J. Design and computational fluid dynamics investi-
gation of a personal, high flow inhalable sampler. Ann Occup Hyg. 2010; 54(4):42742. doi: 10.1093/
annhyg/meq029 PMID: 20418278
Characterization of Airborne Swine Influenza
PLOS ONE | DOI:10.1371/journal.pone.0149083 February 11, 2016 7/8
24. Shu B, Wu KH, Emery S, Villanueva J, Johnson R, Guthrie E, et al. Design and performance of the
CDC real-time reverse transcriptase PCR swine flu panel for detection of 2009 A (H1N1) pandemic
influenza virus. J Clin Microbiol. 2011; 49(7):26149. doi: 10.1128/JCM.02636-10 PMID: 21593260
25. Alonso C, Raynor PC, Davies PR, Torremorell M. Concentration, Size Distribution, and Infectivity of Air-
borne Particles Carrying Swine Viruses. PloS one. 2015; 10(8):e0135675. doi: 10.1371/journal.pone.
0135675 PMID: 26287616
26. Palmberg L, Larsson BM, Malmberg P, Larsson K. Induction of IL-8 production in human alveolar mac-
rophages and human bronchial epithelial cells in vitro by swine dust. Thorax. 1998; 53(4):2604. PMID:
9741367
27. Wang Z, Larsson K, Palmberg L, Malmberg P, Larsson P, Larsson L. Inhalation of swine dust induces
cytokine release in the upper and lower airways. Eur Respir J. 1997; 10(2):3817. PMID: 9042636
28. Urbain B, Mast J, Beerens D, N'Guyen TQ, Goddeeris B, Ansay M, et al. Effects of inhalation of dust
and endotoxin on respiratory tracts of pigs. Am J Vet Res. 1999; 60(9):105560. PMID: 10490071
29. Kim HM, Lee YW, Lee KJ, Kim HS, Cho SW, van Rooijen N, et al. Alveolar macrophages are indispens-
able for controlling influenza viruses in lungs of pigs. J Virol. 2008; 82(9):426574. doi: 10.1128/JVI.
02602-07 PMID: 18287245
30. Knetter SM, Tuggle CK, Wannemuehler MJ, Ramer-Tait AE. Organic barn dust extract exposure
impairs porcine macrophage function in vitro: Implications for respiratory health. Vet Immunol Immu-
nop. 2014; 157(12):2030.
31. Poole JA, Alexis NE, Parks C, MacInnes AK, Gentry-Nielsen MJ, Fey PD, et al. Repetitive organic dust
exposure in vitro impairs macrophage differentiation and function. J Allergy Clin Immun. 2008; 122
(2):37582.e4. doi: 10.1016/j.jaci.2008.05.023 PMID: 18585769
32. Schofield L, Ho J, Kournikakis B. Avian Influenza Aerosol Sampling Campaign in the British columbia
Fraser Valley, 919 April 2004. National Microbiology Laboratory PaPHB, Health Canada; 2005: http://
dycorusa.com/avian%20flu%20final.pdf.
33. Chen PS, Tsai FT, Lin CK, Yang CY, Chan CC, Young CY, et al. Ambient influenza and avian influenza
virus during dust storm days and background days. Environ Health Perspect. 2010; 118(9):12116.
doi: 10.1289/ehp.0901782 PMID: 20435545
34. Choi MJ, Torremorell M, Bender JB, Smith K, Boxrud D, Ertl JR, et al. Live Animal Markets in Minne-
sota: A Potential Source for Emergence of Novel Influenza A Viruses and Interspecies Transmission.
Clin Infect Dis. 2015; 61(9):135562. doi: 10.1093/cid/civ618 PMID: 26223994
35. Ma W, Kahn RE, Richt JA. The pig as a mixing vessel for influenza viruses: Human and veterinaryimpli-
cations. J Mol Genet Med. 2008; 3(1):15866. PMID: 19565018
36. Rabinowitz P, Fowler H, Odofin LO, Messinger C, Sparer J, Vegso S. Swine worker awareness and
behavior regarding prevention of zoonotic influenza transmission. J Agromedicine. 2013; 18(4):304
11. doi: 10.1080/1059924X.2013.826603 PMID: 24125045
37. Roelofs CR, Barbeau EM, Ellenbecker MJ, Moure-Eraso R. Prevention strategies in industrial hygiene:
a critical literature review. AIHA J. 2003; 64(1):627.
38. Ellenbecker MJ. Engineering controls as an intervention to reduce worker exposure. Am J Ind Med.
1996; 29(4):3037. PMID: 8728129
Characterization of Airborne Swine Influenza
PLOS ONE | DOI:10.1371/journal.pone.0149083 February 11, 2016 8/8
... Bioaerosol samples were also collected 25 m upwind and downwind from barns but none of them was IAV positive. [245] n/a; n/a Iowa n/a Real-time RT-PCR Two samplers (NIOSH bioaerosol sampler BC251 and PHISH) were used for assessing the personal exposure of veterinarians in infected barns. The geometric mean IAV concentration was 2094 copies m −3 using the NIOSH sampler and 545 copies m −3 using the PHISH sampler. ...
... Sampling methods affect measurement results. Ref. [245] reported that higher IAV concentrations were derived from a NIOSH BC251 bioaerosol sampler than from a PHISH sampler. Ref. [246] compared an Andersen eight-stage non-viable cascade impactor with a Tisch four-stage non-viable cascade impactor and found the Tisch yield higher airborne viral concentrations than the Andersen impactor. ...
... Limited information is available regarding the size distribution of airborne porcine viruses. Only two studies conducted size-segregated viral measurement [245,246]. Both studies reported that the majority of airborne viruses (IAV, PRRSV, and PEDV) were associated with coarse PM (>4 µm). ...
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Particulate matter (PM) represents an air quality management challenge for confined swine production systems. Due to the limited space and ventilation rate, PM can reach relatively high concentrations in swine barns. PM in swine barns possesses different physical, chemical, and biological characteristics than that in the atmosphere and other indoor environments. As a result, it exerts different environmental and health effects and creates some unique challenges regarding PM measurement and mitigation. Numerous research efforts have been made, generating massive data and information. However, relevant review reports are sporadic. This study aims to provide an updated comprehensive review of swine barn PM, focusing on publications since 1990. It covers various topics including PM characteristics, sources, measurement methods, and in-barn mitigation technologies. As PM in swine barns is primarily of biological origins, bioaerosols are reviewed in great detail. Relevant topics include bacterial/fungal counts, viruses, microbial community composition, antibiotic-resistant bacteria, antibiotic resistance genes, endotoxins, and (1®3)-β-D-glucans. For each topic, existing knowledge is summarized and discussed and knowledge gaps are identified. Overall, PM in swine barns is complicated in chemical and biological composition and highly variable in mass concentrations, size, and microbial abundance. Feed, feces, and skins constitute the major PM sources. Regarding in-barn PM mitigation, four technologies (oil/water sprinkling, ionization, alternation of feed and feeders, and recirculating air filtration) are dominant. However, none of them have been widely used in commercial barns. A collective discussion of major knowledge gaps and future research needs is offered at the end of the report.
... Emerging evidence suggests that airborne transmission is one of the major routes for the spread of viral diseases in animals, such as influenza a virus (IAV) [20,30,31], foot-and mouth disease virus (FMDV) [21,22,32], porcine reproductive and respiratory syndrome virus (PRRSV) [33,34], porcine epidemic diarrhea virus (PEDV) [35], and bovine herpesvirus 1 (BHV-1) [36]. As for pestivirus infection, airborne transmission of CSFV and BVDV is feasible under experimental conditions although they have not been reported in field situations [37,38], suggesting that airborne transmission may contribute to the spread of pestivirus infection. ...
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Background: As a pestivirus of the Flaviviridae family, bovine viral diarrhea virus (BVDV), has imposed a large burden on animal husbandry worldwide, and such virus can be transmitted mainly through direct contact with other infected animals and probably via aerosols. In the present study, we aimed to develop a real-time RT-PCR method for detection of BVDV-1 in aerosol samples. Methods: A pair of primers specific for highly conserved regions of the BVDV-1 5'-UTR was designed. The standard curve and sensitivity of the developed assay were assessed based on 10-fold serial dilutions of RNA molecular standard. The specificity of the assay was evaluated with other pestiviruses and infectious bovine viruses. The clinical performance was examined by testing 169 aerosol samples. Results: The results showed that a good linear relationship existed between the standard curve and the concentration of template. The lowest detection limit was 5.2 RNA molecules per reaction. This assay was specific for detection of BVDV-1, and no amplification was found for other pestiviruses such as classical swine fever virus (CSFV), border disease virus (BDV), and common infectious bovine viruses, including BVDV-2, infectious bovine rhinotracheitis virus (IBRV), bovine parainfluenza virus type 3 (BPIV-3), bovine respiratory syncytial virus (BRSV), bovine ephemeral fever virus (BEFV) and bovine coronavirus (BcoV). The assay was highly reproducible with low variation coefficient values (CVs) for intra-assay and inter-assay. A total of 169 aerosol samples collected from six dairy herds were tested using this method. The results showed that the positive detection rate of BVDV-1 was 17.2% (29/169), which was significantly higher compared with the conventional RT-PCR. Additionally, the positive samples (n = 29) detected by real-time RT-PCR were verified by BVDV RPA-LFD, and a concordance rate of 100% was obtained between them. Conclusions: Taken together, we developed a real-time RT-PCR assay for quantitative analysis of BVDV-1 in aerosol samples, and our finding provided valuable insights into the risk on aerosol transmission of BVDV-1.
... [15][16][17] Clinical and environmental studies have TA B L E 1 Summary of characteristics, inclusion rationale, and recommendations for the polytetrafluoroethylene (PTFE) filter, NIOSH cyclone sampler, and Andersen impactor 21,32 utilized a range of instruments to determine the risk of exposure to virus-laden bioaerosols in health care and agriculture. [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] Limited study sizes underscore the need for consistent approaches across studies in similar settings in order to generate robust comparative data to form clearer conclusions. Bioaerosol sampling devices are essential to the investigation and characterization of IAV bioaerosol emissions and transmission. ...
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Background: Bioaerosol sampling devices are necessary for the characterization of infectious bioaerosols emitted by naturally-infected hosts with acute respiratory virus infections. Assessment of these devices under multiple experimental conditions will provide insight for device use. Objectives: The primary objective of this study was to assess and compare bioaerosol sampling devices using a) an in vitro, environmentally-controlled artificial bioaerosol system at a range of different RH conditions and b) an in vivo bioaerosol system of influenza virus-infected ferrets under controlled environmental conditions. Secondarily, we also sought to examine the impact of NSAIDs on bioaerosol emission in influenza virus-infected ferrets to address its potential as a determinant of bioaerosol emission. Methods: We examined the performance of low and moderate volume bioaerosol samplers for the collection of viral RNA and infectious influenza virus in vitroand in vivo using artificial bioaerosols and the ferret model of influenza virus infection. The following samplers were tested: the polytetrafluoroethylene filter (PTFE filter), the 2-stage National Institute of Occupational Safety and Health cyclone sampler (NIOSH cyclone sampler) and the 6-stage viable Andersen impactor (Andersen impactor). Results: The PTFE filter and NIOSH cyclone sampler collected similar amounts of viral RNA and infectious virus from artificially-generated aerosols under a range of relative humidities (RH). Using the ferret model, the PTFE filter, NIOSH cyclone sampler and the Andersen impactor collected up to 3.66 log10 copies of RNA/L air, 3.84 log10 copies of RNA/L air and 6.09 log10 copies of RNA/L air respectively at peak recovery. Infectious virus was recovered from the PTFE filter and NIOSH cyclone samplers on the peak day of viral RNA recovery. Conclusion: The PTFE filter and NIOSH cyclone sampler are useful for influenza virus RNA and infectious virus collection and may be considered for clinical and environmental settings.
... In fact, only a few studies have looked at the particle size of airborne viruses that can be found in the environment. Anderson 6 stage cascade impactors, National Institute for Occupational Safety and Health (NIOSH) two-stage bioaerosols cyclone samplers [7][8][9], and Sioutas personal cascade impactors [10,11] have been used in agricultural and hospital settings. In all these studies, viruses were found in all air sample stages, meaning that large particles as well as small particles can carry viruses. ...
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Background: The importance of aerosols in the spread of viruses like influenza is still a subject of debate. Indeed, most viruses can also be transmitted through direct contact and droplets. Therefore, the importance of the airborne route in a clinical context is difficult to determine. The aim of this study was to design a chamber system to study the airborne transmission of viruses between ferrets. Methods: A system composed of three chambers connected in series, each one housing one ferret and preventing direct contact, was designed. The chambers were designed to house the ferrets for several days and to study the transmission of viruses from an infected (index) ferret to two naïve ferrets via aerosols and droplets or aerosols only. A particle separator was designed that can be used to modulate the size of the particles traveling between the chambers. The chamber system was validated using standard dust as well as with ferrets infected with influenza A virus. Conclusions: The 50% efficiency cut-off of the separator could be modulated between a 5-µm and an 8-µm aerodynamic diameter. In the described setup, influenza A virus was transmitted through the aerosol route in two out of three experiments, and through aerosols and droplets in all three experiments.
... In fact, a recent study indicates airborne influenza A virion (80-120 nm) bound to organic dust or other particulate matter in the swine barn. 43 To determine the relevance of Type I IFN production, we examined the mRNA expression levels of Type I IFNs (IFN-b, -a) and downstream IFIT1. No significant induction of either was observed similar to responses seen in BEAS-2B cells ( Figure 3E). ...
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Exacerbated inflammation upon persistent barn organic dust exposure is a key contributor to the pathogenesis of lung inflammation and lung function decline. Barn dust constituents and the mechanisms contributing to the exacerbated inflammation are not clearly known. We set out to understand the inflammatory effects of Swine Barn Dust Extracts (SBDE) on human lung epithelial (BEAS2B) and macrophage (THP-1 monocyte derived) cell lines on a kinome array to determine phosphorylation events in the inflammatory signaling pathways. Upon identifying events unique to SBDE or those induced by innate immune ligands in each cell line, we validated the signaling pathway activation by transcriptional analyses of downstream inflammatory cytokines. Our findings indicate that SBDE-mediated pro-inflammatory effects are predominantly due to the induction of neutrophilic chemokine IL-8. Differentially phosphorylated peptides implicated in IL-8 induction in BEAS2B cell line include, TLR2, 4, 5, 7, 8, 9, PKC, MAP kinases (p38, JNK), inflammasomes (NLRP1, NLRP3), NF-κB and AP-1. In the THP-1 cell line, in addition to the aforementioned peptides, peptides corresponding to RIG-I-like receptors (RIG-I, MDA5) were found. This is the first report to demonstrate the application of a kinome array to delineate key inflammatory signaling pathways activated upon SBDE exposure in vitro.
... In farms and abattoirs, samplers were fixed to a tripod roughly one meter above the ground near an active pig pen and run for a minimum of 30 minutes. At the animal markets, mobile bioaerosol sampling localized to animal vendors where nasal washes were collected was conducted by a researcher equipped with a backpack containing the SKC pump with the NIOSH two-stage sampler fixed to one front strap for a minimum of one hour [11]. Mobile bioaerosol sampling was also conducted at the animal markets in the absence of other sampling types; this sampling was generalized, encircling the entire market to mimic a consumer walking up and down aisles of animal and vegetable products. ...
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Background The large livestock operations and dense human population of Southeast Asia are considered a hot-spot for emerging viruses. Objectives To determine if the pathogens adenovirus (ADV), coronavirus (CoV), encephalomyocarditis virus (EMCV), enterovirus (EV), influenza A-D (IAV, IBV, ICV, and IDV), porcine circovirus 2 (PCV2), and porcine rotaviruses A and C (RVA and RVC), are aerosolized at the animal-interface, and if humans working in these environments are carrying these viruses in their nasal airways. Study This cross-sectional study took place in Sarawak, Malaysia among 11 pig farms, 2 abattoirs, and 3 animal markets in June and July of 2017. Pig feces, pig oral secretions, bioaerosols, and worker nasal wash samples were collected and analyzed via rPCR and rRT-PCR for respiratory and diarrheal viruses. Results In all, 55 pig fecal, 49 pig oral or water, 45 bioaerosol, and 78 worker nasal wash samples were collected across 16 sites. PCV2 was detected in 21 pig fecal, 43 pig oral or water, 3 bioaerosol, and 4 worker nasal wash samples. In addition, one or more bioaerosol or pig samples were positive for EV, IAV, and RVC, and one or more worker samples were positive for ADV, CoV, IBV, and IDV. Conclusions This study demonstrates that nucleic acids from a number of targeted viruses were present in pig oral secretions and pig fecal samples, and that several viruses were detected in bioaerosol samples or in the nasal passages of humans with occupational exposure to pigs. These results demonstrate the need for future research in strengthening viral surveillance at the human-animal interface, specifically through expanded bioaerosol sampling efforts and a seroepidemiological study of individuals with exposure to pigs in this region for PCV2 infection.
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Hvordan bør vi indrette vores boliger, kontorer og bygninger i fremtiden, så de bliver mere robuste ift. COVID-19 og kommende pandemier? Det har medicinere fra bl.a. Statens Seruminstitut, ventilationsteknikere og arkitekter sat sig for at undersøge. (How should we design our homes, offices and buildings in the future so that they become more robust in relation to COVID-19 and future pandemics? It has medics from The Statens Seruminstitut, ventilation technicians and architects set out to investigate.)
Chapter
This chapter aims to address the information needs and to encourage the interests of industrial hygienists to apply their skills and knowledge to the population of workers employed in the industrial sectors of agriculture, forestry, and fishing (AFF). Worker health and safety efforts in these three sectors are often lumped together under the category of agricultural health and safety or AFF workers as defined by NIOSH. Other agricultural health and safety reviews have been aimed at health professionals or a more general industrial health and safety professional audience. Herein, we bring the essentials of this subject to an Industrial Hygiene audience, as compared to a general health and safety audience. In order to assist the reader, we organized the sections by the hygienist's paradigm – anticipation, recognition, evaluation, and control. We also discuss how the information provided might be applied to potential policies to stimulate industrial hygiene and safety activity in AFF sectors.
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Der vorliegende Bericht sichtet die weltweit verfügbare Literatur zu Methoden und Ergebnissen von Bioaerosoluntersuchungen in und um Landwirtschaftliche Nutztierhaltung und fasst die wichtigsten Punkte zusammen. Der weltweite Trend der Industrialisierung der Tierproduktion mit regionaler Konzentrierung von Betrieben sowie steigenden Tierzahlen und Besatzdichten führt zu einem Anstieg der Bioaerosolemissionen. Wesentliche Quellen der Bioaerosole sind vor allem die Mikroorganismen auf den Tieren, in ihren Fäkalien, in der Einstreu und im Futter. Werden sie aufgewirbelt emittieren sie mit der Abluft aus den Ställen heraus auch in die Umwelt. Daher wächst die Besorgnis über eine gesundheitliche Beeinträchtigung der Bevölkerung im Umfeld von großen Tierhaltungsanlagen. In der landwirtschaftlichen Nutztierhaltung sind weltweit hunderte verschiedener Viren-, Bakterien- und Schimmelpilzarten nachgewiesen worden, wobei Vertreter der Bakteriengruppe Staphylococcaceae besonders häufig in großer Zahl gefunden wurden. Diese Gruppe scheint somit als spezifischer Leitparameter für Bioaerosole aus der Tierhaltung geeignet. Bioaerosole können Online mit Partikelspektrometern und Offline mit klassischen Methoden gemessen werden, d. h. Probenahme vor Ort mit anschließender Auswertung über kulturbasierte oder molekularbiologische Methoden im Labor. Aufgrund des komplexen Aufbaus von Bioaerosolpartikeln in der landwirtschaftlichen Nutztierhaltung sind Partikelspektrometer nur bedingt zu deren Klassifizierung einsetzbar. Die klassischen Nachweisverfahren sind vor allem zur Detektion von Mikroorganismen besser geeignet. Dabei sollte die Probenahme aufgrund einer Vielzahl unterschiedlicher Sammelverfahren möglichst mit standardisierten Systemen durchgeführt werden, um eine Vergleichbarkeit der Daten zu gewährleisten. Die Systeme sollten zudem eine möglichst hohe physikalische und biologische Sammeleffizienz haben. Die Auswahl eines geeigneten Sammelsystems sollte primär abhängig von der Fragestellung erfolgen. Nach der Sammlung der Bioaerosole erfolgt die Auswertung der Proben meist über Kultivierung von Mikroorganismen und/oder verschiedene biochemische und molekularbiologische Tests. Besonders letztere erlauben, vor allem in Kombination mit kulturbasierten Verfahren, einen detaillierten Einblick in die Zusammensetzung von Bioaerosolen. Hier ist jedoch noch eine weitere Standardisierung der für Bioaerosole geeigneten Methoden notwendig. Endotoxine als Bestandteile von Bioaerosolen werden überwiegend mit dem LAL-Test nachgewiesen, der jedoch relativ störanfällig ist. Die meisten Daten zu Bioaerosolmessungen in der landwirtschaftlichen Nutztierhaltung stehen aus den USA und Deutschland zur Verfügung. Hier wurden in den Ställen von Schweinen, Rindern und Hühnern vor allem die Konzentrationen von Bakterien, Schimmelpilzen und Endotoxinen gemessen. Bei relativ großen Schwankungsbreiten der Ergebnisse bei allen Tierarten wurden die höchsten Konzentrationen luftgetragener Bakterien in Haltungssystemen für Hühner gefunden, gefolgt von Puten, Enten, Schafen, Ziegen, Schweine, Rinder, Pferde und Kaninchen, wobei die verschiedenen Haltungsverfahren und Produktionsstadien einen deutlichen Einfluss auf die Höhe der Konzentrationen haben. Auch publizierte Emissionsfaktoren für luftgetragene Mikroorganismen unterscheiden sich für dieselbe Tierart und Haltungsform teilweise erheblich, hervorgerufen auch durch unterschiedliche Probenahmebedingungen, Sammelmethoden und verschiedene Verfahren zur Bestimmung der Konzentrationen. Bioaerosole wurden bisher ausschließlich Tagsüber gemessen. In den Tierställen können die Konzentrationsunterschiede luftgetragener Bakterien zwischen Tag und Nacht jedoch erheblich sein. Emissionsfaktoren können sich sogar um bis zu 3 Zehnerpotenzen unterscheiden, abhängig von der Tierart. Dies sollte in Zukunft z. B. bei der Berechnung von Jahresmittelwerten berücksichtigt werden. Bei der Transmission, also dem Transport der Bioaerosole über die Luft, sind die Mikroorganismen weitgehend ungeschützt Wind und Wetter ausgesetzt. Wie weit sie getragen werden, ist neben den meteorologischen Bedingungen primär von zwei Parametern abhängig: Die Tenazität, also die Fähigkeit den luftgetragenen Zustand zu Überleben und dem aerodynamischen Durchmesser der Bioaerosolpartikel, der z. B. bestimmt wie schnell diese sedimentieren. Wie lange Mikroorganismen in der Luft lebensfähig bleiben ist wiederum von vielen Faktoren abhängig und nur unzureichend untersucht, letzteres vor allem aufgrund der bisher eingesetzten und nur bedingt geeigneten Testsysteme. Bezüglich der Partikelgröße werden in der landwirtschaftlichen Nutztierhaltung die meisten luftgetragenen Mikroorganismen in deutlich größeren Partikelfraktionen gefunden, als es die Größe der Einzelzellen der Organismen vermuten lässt. Dabei sind 30 % bis 70 % der Bakterien auf Partikeln > 10 µm zu finden, wobei die Verteilung der verschiedenen Bioaerosolbestandteile sehr unterschiedlich sein kann. Auch korreliert die Größenverteilung der Mikroorganismen nicht unbedingt mit der Größenverteilung von Staubpartikeln. Die Konzentrationen von Bioaerosolen in der Immission fallen exponentiell mit der Entfernung zur Emissionsquelle ab. Dies ist primär abhängig von der Partikelgröße und meteorologischen Bedingungen. Anstelle aufwändiger Messungen kann die Ausbreitung von Bioaerosolen auch mit Computermodellen simuliert werden. Bisher überschätzen die Modelle die tatsächlichen Immissionen jedoch meist um ein Vielfaches, da Nachtabsenkung, Partikelgrößenverteilungen und Absterberaten der Mikroorganismen nicht berücksichtigt werden. Aus einer Vielzahl von Publikationen ist seit langem bekannt, dass Bioaerosole, vermutlich synergistisch mit anderen Luftschadstoffen, in Tierställen die Gesundheit des dort arbeitenden Personals und auch der Tiere negativ beeinflussen. Dabei wurde bisher, bis auf die Endotoxine, keine eindeutige Dosis-Wirkungs-Beziehung festgestellt. Es konnte bis heute auch keine eindeutige Aussage über eine etwaige Gefährdung von Anwohnern von Tierhaltungen getroffen werden. Daher sind bisher für Bioaerosole, außer Endotoxine, keine allgemeinen Grenzwerte formuliert, bei deren Überschreitung mit einer schädlichen Wirkung auf die Gesundheit gerechnet werden kann. Stattdessen findet das Vorsorgeprinzip Anwendung und es findet meist eine umweltmedizinische Bewertung von Einzelfällen statt. Um die Bioaerosolemissionen vorsorglich zu reduzieren stehen verschiedene Maßnahmen zur Verfügung. Durch ein gutes Stallmanagement und Hygienekonzept unterstützt durch technische Lösungen wie z. B. die Abluftreinigung kann eine deutliche Reduktion von stallspezifischen Bioaerosolen von weit über 90 % erreicht werden. Ob in Zukunft die Ableitung einer Dosis-/Wirkungsbeziehung für Bioaerosole oder zumindest eine auf validen Daten basierte umweltmedizinische Bewertung der Emissionen gelingt ist offen. Helfen könnten evtl. das Überdenken der stallspezifischen Leitparameter und eine zukünfigt verstärkte Untersuchung von Viren. Dazu gehört auch die Validierung und Weiterentwicklung von High-Volume Sammlern für Bioaerosole, die mit den klassischen Probenahmesystemen nur schwer zu erfassen sind. Bei Ausbreitungsprognosen sollten künftig die Partikelgrößenverteilungen der Mikroorganismen und die unterschiedliche Höhe der Emissionen zwischen Tag und Nacht berücksichtigt werden. Das gilt ebenso für die Tenazität, wobei hier erst neue Messsysteme entwickelt werden sollten, um zu aussagekräftigen Daten zu kommen. Es sollte ebenfalls ein mittelfristiges Ziel sein, die Bioaerosolkonzentrationen bereits im Stall zu senken. Hierzu stehen Konzepte für angepasste Abluftreinigungsanlagen zur Verfügung, die Zusammen mit weiteren Maßnahmen zu einer Reduktion von ein bis zwei Zehnerpotenzen führen können.
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When pathogens become airborne, they travel associated with particles of different size and composition. Particle size determines the distance across which pathogens can be transported, as well as the site of deposition and the survivability of the pathogen. Despite the importance of this information, the size distribution of particles bearing viruses emitted by infectious animals remains unknown. In this study we characterized the concentration and size distribution of inhalable particles that transport influenza A virus (IAV), porcine reproductive and respiratory syndrome virus (PRRSV), and porcine epidemic diarrhea virus (PEDV) generated by acutely infected pigs and assessed virus viability for each particle size range. Aerosols from experimentally infected pigs were sampled for 24 days using an Andersen cascade impactor able to separate particles by size (ranging from 0.4 to 10 micrometer (μm) in diameter). Air samples collected for the first 9, 20 and the last 3 days of the study were analyzed for IAV, PRRSV and PEDV, respectively, using quantitative reverse transcription polymerase chain reaction (RT-PCR) and quantified as geometric mean copies/m3 within each size range. IAV was detected in all particle size ranges in quantities ranging from 5.5x102 (in particles ranging from 1.1 to 2.1μm) to 4.3x105 RNA copies/m3 in the largest particles (9.0-10.0μm). PRRSV was detected in all size ranges except particles between 0.7 and 2.1μm in quantities ranging from 6x102 (0.4-0.7μm) to 5.1x104 RNA copies/m3 (9.0-10.0μm). PEDV, an enteric virus, was detected in all particle sizes and in higher quantities than IAV and PRRSV (p < 0.0001) ranging from 1.3x106 (0.4-0.7μm) to 3.5x108 RNA copies/m3 (9.0-10.0μm). Infectious status was demonstrated for the 3 viruses, and in the case of IAV and PRRSV, viruses were isolated from particles larger than 2.1μm. In summary, our results indicated that airborne PEDV, IAV and PRRSV can be found in a wide range of particle sizes. However, virus viability is particle size dependent.
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Background: Live animal markets have been implicated in transmission of influenza A viruses (IAVs) from animals to people. We sought to characterize IAVs at 2 live animal markets in Minnesota to assess potential routes of occupational exposure and risk for interspecies transmission. Methods: We implemented surveillance for IAVs among employees, swine, and environment (air and surfaces) during a 12-week period (October 2012-January 2013) at 2 markets epidemiologically associated with persons with swine-origin IAV (variant) infections. Real-time reverse transcription polymerase chain reaction (rRT-PCR), viral culture, and whole-genome sequencing were performed on respiratory and environmental specimens, and serology on sera from employees at beginning and end of surveillance. Results: Nasal swabs from 11 of 17 (65%) employees tested positive for IAVs by rRT-PCR; 7 employees tested positive on multiple occasions and 1 employee reported influenza-like illness. Eleven of 15 (73%) employees had baseline hemagglutination inhibition antibody titers ≥40 to swine-origin IAVs, but only 1 demonstrated a 4-fold titer increase to both swine-origin and pandemic A/Mexico/4108/2009 IAVs. IAVs were isolated from swine (72/84), air (30/45), and pen railings (5/21). Whole-genome sequencing of 122 IAVs isolated from swine and environmental specimens revealed multiple strains and subtype codetections. Multiple gene segment exchanges among and within subtypes were observed, resulting in new genetic constellations and reassortant viruses. Genetic sequence similarities of 99%-100% among IAVs of 1 market customer and swine indicated interspecies transmission. Conclusions: At markets where swine and persons are in close contact, swine-origin IAVs are prevalent and potentially provide conditions for novel IAV emergence.
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