Characterization of Bioaerosols from Cage-housed and Floor-housed Poultry Operations

Abstract

Background. Dust and endotoxin levels are higher in bioaerosols from floor-housed (FH) poultry operations than cage-housed (CH) poultry facilities. Workers from CH operations have reported a greater prevalence of respiratory symptoms than FH workers. The negative respiratory symptoms observed in workers are typically attributed to endotoxin. However, other components of poultry bioaerosols and their effects on human health, such as bacteria, antibiotics and archaea, are poorly understood. Bacteria have been detected in intestinal, fecal, litter, and air samples from poultry operations. Chicken fecal bacteria differ depending on bird age and antibiotic use, which differ between CH and FH facilities. Antibiotics are used in CH and FH poultry operations to lower the likeliness of disease transmission. In FH facilities, antibiotics may also be used at sub-therapeutic levels for growth promotion. Low levels of antibiotic create a selective pressure towards antimicrobial resistance (AMR) in chicken fecal bacteria. Archaea have been detected in ceca, fecal, litter and house fly samples from poultry facilities but have not been investigated in bioaerosols. However, archaea have been detected in swine and dairy bioaerosols and can induce airway inflammation. Further understanding of poultry bioaerosols, with a comparison of those from CH and FH operations, will aid in the development of management practices to reduce worker exposure and response. Objective. The objective of these studies was to compare bioaerosols from CH and FH poultry facilities. Specifically, levels of dust, endotoxin, total bacteria, bacterial species, antimicrobial resistance genes and methanogenic archaea were examined. Methods. Bioaerosols were collected from fifteen CH and fifteen FH poultry operations using stationary area samplers as well as personal sampling devices. Dust was measured by gravimetric analyses. Limulus Amoebocyte Lysate (LAL) assays were used to quantify endotoxin. Bacteria and archaea concentrations were measured by quantitative PCR. Bacterial and archaeal diversity was investigated using PCR followed by denaturing gradient gel electrophoresis (DGGE) and sequencing. AMR genes were detected using end-point PCR. Results. Dust (p<0.001), endotoxin (p<0.05), total bacteria (p<0.05), Enterococcus (p<0.001), E. coli (p<0.001) and Staphylococcus (p<0.001) were more concentrated in bioaerosols from FH poultry operations than CH bioaerosols. Methanogenic archaea (p<0.001) and C. perfringens (p<0.05) were significantly higher in bioaerosols from CH facilities than FH bioaerosols. Zinc bacitracin resistance gene (bcrR), erythromycin resistance gene (ermA), and tetracycline resistance gene (tetA/C), were more prevalent in bioaerosols from FH facilities than CH bioaerosols (p<0.01, p<0.01 and p<0.05, respectively). Conclusions. Bioaerosols from CH and FH poultry operations are significantly different, suggesting that CH and FH workers are exposed to significantly different environments. Bacterial diversity, C. perfringens, archaea, and/or unmeasured components of bioaerosols may be contributing to the greater prevalence of respiratory symptoms observed in CH workers. Each barn type may require specific remediation methods. Future directions. In order to better understand the role of bioaerosols in poultry worker respiratory dysfunction, it will be necessary to examine airway inflammation following exposure to bioaerosols, or components of bioaerosols, from each poultry barn type.