Characterization of Fungal Bioaerosols on Dairy Farms During the Winter Season

Milk production in France represents a major agro-economic sector. Dairy farms provide an environment conducive to the formation and dispersion of fungal bioaerosols originating from various environmental reservoirs present on farms (manure, straw, hay, bedding, silage, etc.), to which both farmers and cattle are potentially exposed. In 2022, the World Health Organization (WHO) published a report identifying certain fungal species as priority pathogens. Among these pathogens are molds commonly detected in aerosols. It is therefore necessary to characterize fungal communities present in dairy farms, including bioaerosols and different matrices. To characterize the mycobiota of air and the different matrices (feed, bedding, manure, water), 12 dairy farms were selected in Normandy and monitored during the winter season when cows remain indoors. Air samples were collected during various farming tasks (feeding, bedding, milking), and the different matrices were also studied. Molds were isolated and identified using microscopic and molecular methods. Physical data (temperature, relative humidity, particles number) were also collected during sampling. Species belonging to the genus Aspergillus (A. fumigatus in bioaerosols; A. tubingensis in feed and bedding), the genus Penicillium and its related species (Talaromyces piceae in bioaerosols; Penicillium series Roquefortorum in feed) and those of the Mucorales order (Mucor in bioaerosols, bedding and manure; Lichtheimia in feed) were the most recurrent species in dairy farms included in our study. Mulching is the activity that generates higher level of particles (p = .025), resulting in exposure mainly to Aspergillus (A. tubingensis: 417.5 CFU/m3) and Mucorales (Lichtheimia: 668.2 CFU/m3, Rhizopus: 131.8 CFU/m3 and Absidia: 127.3 CFU/m3). This study highlighted significant fungal diversity in bioaerosols, feed, bedding, and manure from dairy farms. The issue of fungal aerosolization was also addressed by observing transfer of strains from feed, bedding, and manure into the air during handling.