Laboratory animal allergy : allergen exposure assessment and epidemiological study of risk factors

The main objective of the study presented in this thesis was to estimate the prevalence rate of laboratory animal allergy and to determine its association with risk factors, like allergen exposure level, atopy, gender and other host factors. A cross-sectional survey was undertaken among 540 workers at 8 laboratory animal facilities. All participants completed a questionnaire and underwent skin prick testing with common and occupational allergens. Total and specific IgE measures were obtained. Prevalence rates of allergic symptoms (chest tightness (asthma), eye/nose and/or skin) due to working with rats or mice were 19% and 10%, respectively. The most common symptoms were eye/nose symptoms, 17% and 9% and asthmatic symptoms were found in 6% and 3% of the workers, respectively. The prevalence rate of sensitisation to rat or mouse allergens was 18% and I I%. Symptoms and sensitisation were strongly correlated. However, not all symptoms seemed to be IgE mediated. Rat and mouse allergy, defined as allergic symptoms accompanied by sensitisation, was highly associated with elevated total IgE (≥100 kU/1) and positive skin prick response to common allergens. The relationship between rat and mouse allergy and positive skin prick response to common allergens, could be completely explained by a specific response to cat or dog fur allergens.Stationary and personal air sampling was performed to identify determinants of exposure and estimate the animal allergen exposure. Animal caretakers experienced the highest exposure to aeroallergens. However, large variation within each job title was present. This may result from the wide range of tasks performed, of which handling contaminated bedding or conscious rats or mice showed the highest exposure. A relationship between allergen exposure and rat allergy became visible after excluding workers with four or more years of exposure to laboratory animals. This relationship was clearly visible for the atopic workers (having an pet allergy and/or elevated total serum IgE). The effect of exposure on rat allergy varied between atopic and non-atopic workers. Atopy should therefore be considered as an effect modifier of exposure. A higher prevalence rate of rat allergy was also found for men and smokers. However, these associations were not statistically significant.