The detrimental effects of poor ambient air quality, in particular fine dust (particulate matter), on human respiratory health are extensively studied and well known, in contrast to (farm) animals. Agricultural environments, in particular stables, are important sources of organic dust and emissions of other air pollutants like ammonia. In animals poor air quality induces airway inflammation and pneumonia, but the exact contributing factors and mechanisms are poorly understood. To maintain animals healthy for economic (and welfare) reasons farmers and their vets rely on antimicrobial mass medication. The consequence are high levels of antimicrobial resistance in different farm animal production systems, and Belgium keeps on struggling to rationally reduce this antimicrobial use.

In a previous BOF project (01D25016) of our group, granted to Katharina van Leenen, the worrisome observation was that 40% of Belgian calves suffered from pneumonia, while not detected, and > 80% had neutrophilia in the airways, a sign of inflammation. In that project we also evidenced for the first time that particulate matter and airborne endotoxin, together with other ambient air parameters, are associated with calf pneumonia. This study had a cross-sectional design, which made it impossible to make hard conclusions.

In this follow up project we want to evidence several of the hypotheses raised from the preliminary work. The effects of particulate matter (PM₁₀, PM_2.5, PM_1.0) and endotoxin concentrations on airway inflammation in calves will be studied, both by longitudinal observational studies in field situations as by experimental challenge studies. Focus is on characterization of the inflammatory response to dust exposure (flow cytometry, gene expression,…) in broncho-alveolar lavage fluid. These studies will provide better insights into the complex relationship between air quality, host defenses (innate and acquired immunity) and infectious agents. This information will help to establish recommendations for stable air quality for calves, guidelines for adequate problem herd investigations and evidence-based intervention measures to improve stable climate. This research has great potential to reduce airway inflammation and pneumonia, both by non-infectious as infectious agents, by making effective prevention possible. As a consequence, economic losses and animal suffering will be reduced, as well as irrational antimicrobial use, all contributing to more sustainable cattle farming in Belgium, with renewed societal support.

Interesting spill-over effects to human health are possible. The relationship between farming environments and human respiratory health is ambiguous: some farming situations reduce asthma, while in others the risk for respiratory diseases is increased. Also, spatial planning in Belgium, creates very close contact between farms and surrounding houses, exposing these inhabitants to stable emissions. This project will deliver objective information on stable air quality, which can aid to better characterize occupational exposure for farmers and farm visitors, as well as potential impacts (positive or negative) for families living nearby. The cytological information from repeated invasive sampling (broncho-alveolaire lavage) of animals will also be unique, compared to what is possible in humans.