Abstract

In a previous issue of the European Respiratory Journal, Dosman et al. 1 reported on four cases of occupational asthma in newly employed workers in the large, recently developed, swine production facilities in Saskatchewan (Canada). All were full-time employees and all developed symptoms suggestive of asthma within a short time of commencing employment. None of the cases had a history of asthma, allergy symptoms or previous exposure to indoor air contaminants of swine confinement facilities. Work in swine buildings has been associated with respiratory symptoms, reductions in mean and across-shift lung function values 2, and increased bronchial responsiveness 3, 4. Asthma has been reported in swine workers, but this has typically occurred in workers with lengthy employment 5, 6.

Cases 1–3 in our initial report showed some reaction to skin-prick allergy tests. While forced expiratory volume in one second (FEV1) for case 1 was relatively stable over time, provocation challenge causing a 20% fall in FEV1 (PC20) was reduced for several months following resignation from the swine barn. Case 1 also experienced symptoms requiring removal from the barn during a re-entry challenge. It was speculated that these cases might exhibit a type of occupational asthma, described by Brooks et al. 7, as "not-so-sudden onset" nonallergic asthma resulting from irritant exposure over a number of months.

Since the initial study 1, we have encountered three additional cases that have been labelled as cases 5, 6 and 7 (table 1). In contrast to the previous four cases, the cases reported herein are all male. Again, none of the cases had a history of asthma or wheeze and none had reported previous regular occupational exposures in a swine confinement facility. Each of the cases developed symptoms within weeks to months of commencing employment and each has had continued sensitivity to exposures in a swine barn.

Case 5 was a 48-yr-old ex-smoker who began working in the swine industry in late 2002. Within 6 months of employment, he began to have respiratory symptoms, which eventually led to a severe episode several months after commencement of work. Pulmonary function showed evidence of mild airways obstruction, but a post-bronchodilator test was not conclusive. He underwent methacholine challenge testing where FEV1 decreased by 18% at 4 mg·mL-1, compatible with a mild increase in airways responsiveness. However, overall PC20 was not calculable because, at 8 mg·mL-1, the decrease in FEV1 was 12%. He exhibited mild skin-prick test reactivity to shellfish and house dust, along with strong reactivity to grain dust. He improved while away from work but continues to work part time at the swine facility.
Case 6 was a 47-yr-old ex-smoker. He began working in the swine barns in early 2003. Shortly after commencing work, he developed respiratory symptoms, which improved away from work. After 1 yr, he resigned from work. FEV1 at the clinic was 3.36 L while PC20 was 1.95 mg·mL-1. He had a mild skin-prick test reaction to house dust mite. Since resigning, he continues to be bothered by cough and wheeze, as well as continuing to use fluticasone propionate b.i.d. (GlaxoWellcome Inc., Mississauga, ON, Canada).

We have less information for case 7, a 30-yr old who had spent 1 yr working in a swine barn 10 yrs ago. He developed cough and wheeze shortly after commencing, which continued after quitting the barn. Allergy skin-prick testing and pulmonary function testing was not completed.

The addition of these new cases to the previous case series 1 leads us to believe that the extent of this condition may be more common than originally suspected, and that some newly employed workers in swine confinement facilities are at risk of developing a form of asthma identified as "not-so-sudden onset asthma" 7. Pre-employment assessments and frequent early employment monitoring of workers may be important tools in addressing early respiratory effects in workers in this industry. Finally, we believe that studying this population would provide further insight into the mechanisms by which occupational asthma occurs among workers in these facili

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