Assessment of bioaerosols at a concentrated dairy operation
Increased bioaerosol loadings in down- wind plumes from concentrated animal feeding oper- ations (CAFOs) may increase the risk for allergy and infection in humans. In this study, we monitored airborne concentrations of culturable bacteria and fungi at upwind (background) and downwind sites at a 10,000 milking cow dairy over the course of a year. The average bacterial concentrations at the upwind site were 8.4 9 10 3 colony forming units (CFU) m -3 and increased to 9.9 9 10 5 CFU m -3 at the down- wind edge of the cattle lots, decreasing to 6.3 9 10 4 CFU m -3 200 m farther downwind. At the same sites, the average fungal concentrations were 515, 945, and 1,010 CFU m -3 , respectively. Significant correla- tions between the ambient weather conditions and airborne fungal and bacterial concentrations were identified. Sequence analysis of PCR-amplified DNA from bacterial clones and fungal isolates revealed genus and species level differences between upwind and downwind sites. Although we could not cultivate gram-negative bacteria, bacterial clones at downwind sites identified as being gram-negative matched with the following genera: Acinetobacter, Bradyrhiz- obium, Escherichia, Idiomarina, Methylobacterium, Ralstonia, and Novosphingobium. Fungal isolates from downwind matched with the following genera: Acremonium, Alternaria, Ascomycte, Aspergillus, Basidiomycete, Cladosporium, Davidiella, Doratomy- ces, Emericella, Lewia, Onygenales, Penicillium, Rhizopus, and Ulocladium. None of the bacterial and fungal sequence matches were affiliated with genera and species known to be pathogenic to humans. Overall, the data suggest that exposure to bioaerosols in the downwind environment decreases with increas- ing distance from the open-lot dairy.