This is the question that Drs. Carmen Alonso, Sagar Goyal, Peter Davies, and Montse Torremorell from the College of Veterinary Medicine studied in collaboration with Drs. Bernard Olson and Peter Raynor from the College of Science and Engineering and the School of Public Health respectively, in the following paper published in Aerosol Science and Technology this past month.
In this study, the team form the University of Minnesota compared the capacity of two different air samplers to detect PRRSv and SIV in an experimental setting. The challenge to detect viral aerosol is to find a technique capable of capturing small amount of virus in a large amount of air. This experiment found that the particle size, the media used for collection as well as the extraction technique (passive or active) all had a significant effect on the detection of the viruses.
Abstract: Detection and quantification of dilute viral aerosols, as encountered outside animal housing facilities, requires methods that are able to detect small numbers of viruses in large volumes of air. This study compared the performance of two size-differentiating cascade impactors; an Andersen 8-stage (ACI; 28.3 L/min) and a high volume Tisch (TCI; 1,133 L/min) to assess sampling efficiency for detecting porcine reproductive and respiratory syndrome virus (PRRSV) and influenza A virus (IAV). Samples of particles sorted by aerodynamic diameter were analyzed by quantitative polymerase chain reaction (qPCR) and collection efficiency was assessed by particle size. Collection media (minimum essential medium [MEM] and beef extract [BE]), elution technique (active versus passive), and sampling times (10, 20, and 30 min) were variables assessed for the TCI sampler. Extraction efficiency was 35% higher with BE as compared to that of MEM (p = 0.0007); active extraction technique was 19% more efficient than the passive technique (p = 0.03); time of sampling did not significantly affect the amount of virus recovered. The ACI sampler was more efficient in detecting both viruses from small and medium sized airborne particles (≤3 μm) as compared to the TCI sampler (p < 0.001). The latter sampler, however, was more efficient at IAV detection from large airborne particles (>3 μm) (p = 0.0025) indicating the potential of this sampler in detecting the presence of small amounts of viruses in aerosols under field conditions.
In 2015, the Midwestern part of the United States was the theater of an outbreak of a highly pathogenic strain of avian influenza. Drs. Torremorell, Alonso and Davies from the University of Minnesota were involved during the epidemic and just published in Avian Diseases and their findings concerning the airborne transmission of the virus were just published in Avian Diseases.
The study showed that the air exhausted from an infected poultry facility was a source of contamination for the environment but also a risk of transmission for Highly Pathogenic Avian Influenza (HPAI) that needs to be seriously taken into consideration. Indeed, live and infectious virus was found at a distance up to 70m (76.5 yards) from the farm facilities.
Abstract: We investigated the plausibility of aerosol transmission of H5N2 highly pathogenic avian influenza (HPAI) virus during the 2015 spring outbreaks that occurred in the U.S. midwest. Air samples were collected inside and outside of infected turkey and layer facilities. Samples were tested to assess HPAI virus concentration (RNA copies/m3 of air), virus viability, and virus distribution by particle size. HPAI virus RNA was detected inside and up to 1000 m from infected facilities. HPAI virus was isolated from air samples collected inside, immediately outside, up to 70 m from infected facilities, and in aerosol particles larger than 2.1 lm. Direct exposure to exhausted aerosols proved to be a significant source of environmental contamination. These findings demonstrate HPAI virus aerosolization from infected flocks, and that both the transport of infectious aerosolized particles and the deposition of particles on surfaces around infected premises represent a potential risk for the spread of HPAI.
Dr. Alonso who just graduated from her PhD at the University of Minnesota, published in collaboration with Drs. Davies, Morrison and Torremorell an article evaluating the electrostatic particle ionization (EPI) technology as a technique to reduce particle load in the air. The results showed that EPI was the most efficient when the system was close to the particle source and when the particle size was between 3.3 and 9 μm no matter what swine pathogen was evaluated. This technique could be promising in decreasing the risk of disease transmission between swine facilities.
Abstract Influenza A virus (IAV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine epidemic diarrhea virus (PEDV) and Staphylococcus aureus are important swine pathogens capable of being transmitted via aerosols. The electrostatic particle ionization system (EPI) consists of a conductive line that emits negative ions that charge particles electrically resulting in the settling of airborne particles onto surface s and potentially decreasing the risk of pathogen dissemination. The objectives of this study were to determine the effect of the EPI system on the quantity and viability of IAV, PRRSV, PEDV and S. aureus in experimentally generated aerosols and in aerosols generated by infected animals. Efficiency at removing airborne particles was evaluated as a function of particle size (ranging from 0.4 to 10 μm), distance from the source of ions (1, 2 and 3 m) and relative air humidity (RH 30 vs. 70 %). Aerosols were sampled with the EPI system ‘‘off’’ and ‘‘on.’’ Removal efficiency was significantly greater for all pathogens when the EPI line was the closest to the source of aerosols. There was a greater reduction for larger particles ranging between 3.3 and 9 μm, which varied by pathogen. Overall airborne pathogen reduction ranged between 0.5 and 1.9 logs. Viable pathogens were detected with the EPI system ‘‘on,’’ but there was a trend to reducing the quantity of viable PRRSV and IAV. There was not a significant effect on the pathogens removal efficiency based on the RH conditions tested. In summary, distance to the source of ions, type of pathogen and particle size influenced the removal efficiency of the EPI system. The reduction in inf ectious agents in the air by the EPI technology could potentially decrease the microbial exposure for pigs and people in confinement livestock facilities.
One flu, many colors: that is the title of the latest article published in the National Hog Farmer by two faculty members from the University of Minnesota, Drs. Culhane and Rovira. If it is common to talk about one influenza especially in the One Health initiative which reminds us that human and animal health are intricately related, the authors also emphasize that there are “many variants of influenza A viruses [which] paint a complicated picture, sometimes with colors too numerous to grasp with quick glances.”
Because influenza is common to swine, poultry, and human, there are many differences among the strains, enhanced by the variations found between and within geographic locations. This is why our experts recommend to characterize the virus, and go one step further than the one test common to all influenza A.
As they put it themselves, “Influenza A viruses are fascinating, challenging and dynamic” and it is important to determine their colors.
Dr. Torremorell, director of the Swine Disease Eradication Center published a new study on the persistence of Influenza A virus in air and on surfaces of swine production facilities.
Abstract: Indirect transmission of influenza A virus (IAV) in swine is poorly understood and information is lacking on levels of environmental exposure encountered by swine and people during outbreaks of IAV in swine barns. We characterized viral load, viability and persistence of IAV in air and on surfaces during outbreaks in swine barns. IAV was detected in pigs, air and surfaces from five confirmed outbreaks with 48% (47/98) of oral fluid, 38% (32/84) of pen railing and 43% (35/82) of indoor air samples testing positive by IAV RT-PCR. IAV was isolated from air and oral fluids yielding a mixture of subtypes (H1N1, H1N2 and H3N2). Detection of IAV RNA from air was sustained during the outbreaks with maximum levels estimated between 7 and 11 days from reported onset. Our results indicate that during outbreaks of IAV in swine, aerosols and surfaces in barns contain significant levels of IAV potentially representing an exposure hazard to both swine and people.