Mould and farming revisted

Respiratory diseases among grain farmers has already been described in the Middle Ages.  In 1932 Campbell reported farmers’ lung disease occurring in British farmers handling mouldy hay. Pepys identified in 1962 the causal agents of this form of hypersensitivity pneumonitis as spores from thermophilic actinomycetes. These microorganisms are not moulds, but Gram-negative bacteria that resemble moulds by filamentous growth and production of large numbers of spores.  Later studies have shown that numerous fungal species can induce attacks of hypersensitivity in farmers as well as other occupations with exposure to fungal spores.   Farmers are exposed to multiple agents originating from microbial, plant and animal sources.  In spite of this, most epidemiological studies of farmers have only measured exposure a limited number of agents, typically endotoxins, dust and ammonia. Thus the role of other agents is mainly unclear.    In an epidemiological study of Norwegian farmers exposure to a number of bioaerosol agents was estimated and exposure-response modeling demonstrated that fungal spores were most strongly associated with acute mucous irritation symptoms and non-allergic asthma, while atopic asthma showed the strongest negative associations with fungal spores.  Further modeling of long term respiratory outcomes as chronic bronchitis, lung function and COPD was complicated by correlated exposure estimates prohibiting identification of the most important agents.  However, farmers are exposed to fungal spores and endotoxins at levels that vastly exceed proposed guidelines, indicating that these agents are likely to play a role in respiratory diseases in farmers.   In conclusion: Exposure fungal spores are likely to play a role in respiratory diseases among farmers as well as endotoxins and other bioaerosol agents.      This presentation will give an update of the literature on bioaerosol agents involved in respiratory diseases among farmers with special focus on moulds.