Design, construction and validation of a nose-only inhalation exposure system to measure infectivity of filtered bioaerosols in mice.

AIMS The aim of this project was to validate a method to deliver a reproducible, selected dose of infective bioaerosol through a respiratory protective technology to an animal that exhibits a proportional clinical response. METHODS AND RESULTS The Controlled Aerosol Test System (CATS) was designed to generate and condition a viable infective aerosol, pass it through a treatment technology and thence to the breathing zone of a mouse constrained in a Nose-Only Inhalation Exposure System (NOIES). A scanning mobility particle sizer and impingers at sampling ports were used to show that viability is preserved and particle size distribution (PSD) is acceptably uniform throughout the open CATS, including the 12 ports of the NOIES, and that a particle filter used caused the expected attenuation of particle counts. CONCLUSIONS Controlled Aerosol Test System delivers uniformly to mice constrained in the NOIES a selectable dose of viral bioaerosol whose PSD and viable counts remain consistent for an hour. SIGNIFICANCE AND IMPACT OF THE STUDY This study's characterization of CATS provides a new test system in which a susceptible small-animal model can be used as the detector in a quantitative method to evaluate the ability of respiratory protective technologies to attenuate the infectivity of an inspired pathogenic aerosol. This provides a major improvement over the use of viable bioaerosol collectors (e.g. impactors and impingers), which provide data that are difficult to relate to the attenuation of pathogenicity.