Laboratory animal allergy, Long-term incidence, effects on lung function, individual risk factors

The aim was to study and prospectively follow symptoms and sensitisation of laboratory animal workers with laboratory animal allergy (LAA) and workers at risk for development of LAA in terms of latency time, incidence, prevalence and possible health selection. Furthermore, the impact of animal positive skin prick tests (SPT) on lung function and individual risk factors for development of LAA was studied. Thirty percent of animal exposed workers had developed LAA symptoms, one third of those had LAA asthma and two thirds were SPT positive to laboratory animals. The retrospective mean latency time before onset of symptoms in SPT positve subjects was about two years. The long-term incidence of LAA symptoms and sensitisation was 2.1 and 0.5 cases per 100 person-years respectively. The level of sensitisation, measured as the weal area of SPT reactions and total serum IgE levels, remained unchanged at follow-up. Sensitisation to laboratory animals did not affect baseline lung function but was associated with increased airway responsiveness. The tendency of health selection in the first study was accelerated during the follow-up period and especially LAA asthma cases stopped working with laboratory animals. Risk factors for developing LAA asthma were parental and childhood allergy, raised total serum IgE levels (>100 kU/L) and positive SPT to environmental allergens. Furthermore, LAA was associated with HLA-DR4 and particular Gm genes and a possible "protective effect" of HLA-B16 was found indicating the polygenic inheritance of the immune response in atopy. The short latency time and the low long-term incidence of LAA suggest an early development of LAA in susceptible individuals.