Evaluation of an Air Tester for the Sampling of Aerosolized Equine Herpesvirus-1
Air sampling devices have been developed and are routinely used in pharmaceutical, medical and industrial settings to document the presence of air-borne pathogens. The aim of this study was to evaluate the capability of a commercially available air tester to sample aerosolized equine herpesvirus-1 (EHV-1) for detection by real-time PCR.
A commercial EHV-1 whole virus vaccine (Rhinomune, Pfizer Animal Health, New York, NY, USA) was nebulized at different doses, followed by the collection of air samples and environmental swabs at different distances from the nebulizer (shedding source). Air samples (500 l) were collected using a portable air monitoring system(M Air T, Millipore, Billerica, MA, USA) at 14.5, 9.6, 4.8, 1.5 and 0.5 m from the nebulizer. The principle of the portable air tester used in this study is based on the sampling of a pre-determined air volume through a sieve directly onto a retrievable agar plate. During the entire study event (from the beginning of nebulization to the collection of the last sample) 40 cm rayon swabs(Fox Converting Swabs, Green Bay, WI, USA) previously soaked in PBS were left in the room in a vertical position at 14.5, 9.6, 4.8, 1.5 and 0.5 m from the nebulizer to document environmental contamination with EHV-1. Following the last sample collection, PBS soaked rayon swabs were collected from the gloves, surgical mask, coat and hair from the person performing the experiment. The collected samples (agar plates and swabs) were processed for nucleic acid purification within 1 hour of collection using an automated nucleic acid extraction system (CAS-1820 X-tractor Gene, Corbett Life Science, Sydney, Australia). All purified DNA samples were assayed for the presence of the glycoprotein B (gB) gene of EHV-1 by real-time TaqMan PCR and the results were expressed as EHV-1 gB gene copies per liter of sampled air or whole swab.
The detection of EHV-1 in air samples and swabs correlated directly with the nebulized dose as well as the distance at which the samples were collected. Swabs collected from gloves, mask and coat of the person performing the experiment tested PCR positive for EHV-1 when high doses of EHV-1 were nebulized.
In conclusion, the study results have shown that aerosolized EHV-1 can be sampled from the air via a commercial air tester for real-time PCR detection. The air sampling protocol used for the study will require more validation and optimization for detection limits using naturally or experimentally infected horses in the future. The study has also shown that environmental swabs may capture aerosolized EHV-1 virus and that the virus may be detected from gloves, coat and mask of attending personnel. The risk of contaminated environment and personnel needs to be further investigated as possible transmission source.