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As a result of the unprecedented highly pathogenic avian influenza (HPAI) outbreak in the U.S. in 2014-2015, some egg producers in the U.S. started using inlet air filtration to reduce the risk of disease transmission by air into hen houses. The removal efficiency of particulate matter (PM), the carrier of airborne pathogens, by such filtration systems has not been investigated. Therefore, this field study was conducted to evaluate the PM removal efficacy of an electrostatic air filtration system (consisting of a low-grade air filter and an electrostatic particle ionization, or EPI, system) installed at the inlet of a commercial high-rise hen house. The evaluation was performed in two test rounds over a one-year period. Results showed that average PM removal efficiencies in round 1 (spring to summer) and round 2 (late fall to spring) were respectively 66% and 29% for PM1, 66% and 30% for PM2.5, 66% and 31% for PM4, 68% and 36% for PM10, and 68% and 45% for total PM. Removal efficiency became unstable when the EPI system was inactive (i.e., when solely relying on the filter for PM removal). House static pressure and ventilation rate indicated considerable clogging of the filter media by dust accumulation and the need for replacement after ~16 weeks of use in the spring-to-summer sampling period (round 1); however, clogging was not an issue during the entire late fall-to-spring sampling period (24 weeks, round 2). The appearance of the filter changed gradually as dust accumulated with time, which can be captured by image analysis and used to judge filter dirtiness and lifespan. The findings of this field study provide insight into the efficacy of PM removal by such a low-cost air filtration system, which will help egg producers in their decision-making for disease prevention strategies. [ABSTRACT FROM AUTHOR]

The airflow in and around poultry houses was studied numerically with the goal of determining the disease spread characteristics and comparing two ventilation schemes. A typical manure-belt laying hen egg production facility was considered. The continuity, momentum, and energy equations were solved for flow both inside and outside poultry houses using the commercial computational fluid dynamics (CFD) code FLUENT. The geometry was constructed by making some simplifying assumptions, such as two-dimensionality. The spread of virus particles was considered analogous to diffusion of a tracer contaminant gas, in this case ammonia (NH3). The effect of thermal plumes produced by the hens in the poultry house was also taken into consideration. Two ventilation schemes with opposite flow directions were compared. Contours of temperature and contaminant mass fraction for both cases were obtained and compared. The analysis shows that ventilation and air quality characteristics were much better for the case in which the airflow was from bottom to top instead of from top to bottom (top to bottom is how most current poultry houses are configured). This has implications for air quality control in the event of epidemic outbreaks. Decreased contaminant spread to downwind poultry houses was observed in the bottom-to-top airflow scheme. [ABSTRACT FROM AUTHOR]