[Chronic obstructive bronchitis in a fodder farming setting].

Respiratory disease in agricultural workers are dominated both in terms of frequency and severity by chronic obstructive long disease. In the Doubs, in dairy cereal farmers, the prevalence of chronic bronchitis in active farm workers is around 10 per cent, and 6 per cent are non-smokers. It is twice the level of the control population of non-exposed subjects. The frequency is most elevated in the men and increases both with age and with altitude. A longitudinal study of male farm workers aged more than 45 has shown that there is an abnormally rapid loss of forced expired volume in one second (FEV1). Two different studies carried out in the Doubs have revealed epidemiological, respiratory function and immunological arguments in favour of immuno-allergic mechanisms. Notably, obstructive chronic bronchitis (OCB) occurs more frequently in agricultural workers with a previous history of farmer's lung or previous sub-acute delayed symptoms in relation to exposure. On the other hand, there are no close links between OCB and the intensity of antigenic exposure (the total quantity of fodder handled). By contrast, there is a relationship between exposure to thermophillic actinomycetes (antigen of farmer's lung) and OCB. The frequency of serum precipitins is most elevated in farm workers with OCB than in asymptomatic agricultural workers. Finally, non-smokers who are suffering from OCB without evidence of farmer's lung, have a respiratory function profile and also alveolar lavage cell pattern characteristic of extrinsic allergic alveolitis after provocation tests to mouldy hay. These arguments are in favour of immuno-allergic mechanisms in the pathogenesis of chronic bronchitis in farm workers which seems to be well differentiated from chronic bronchitis due to smoking.