Farmer´s children and atopy

Research project P 14015 Farmers`s children and atopy Josef RIEDLER 11.10.1999 Allergic diseases in children are on the rise. Some studies have found a lower prevalence of hay fever and allergic asthma in children from rural areas than in children living in an urban environment. Air pollution has been suggested t explain this difference but the scientific evidence is controversial. Recently, we found a lower prevalence of hay fever (3.1% vs 10.3%, p=0.0002), asthma (1.1 % vs 3.9%, p=0.017) and a positive skin prick reactivity to at least one of the common local allergens (18.8% vs 32.7%, p=0.00 1) in children living on a farm than in children from a non-farming environment. In a multivariate logistic regression model, adjusting for genetic background, parent education, living and housing conditions and dietary factors did not change the odds ratio for the association of fanning and allergic sensitisation. Only after including `regular contact with livestock and poultry` into the model did the odds ratio change significantly (cOR 0.48 [95% CI 0.30-0.75] to aOR 0.75 [95% CI 0.37-1.52]) indicating an association between regular contact with farm animals and reduced risk of atopic sensitisation. We speculate that bacteria] wall derived substances like lipopolysaccharides (endotoxin) are more prevalent in the fanning environment and that these substances stimulate the maturation of Th-1 cells and suppress an allergic Th-2 response in children. The aim of the present project is to test the hypothesis that the amount of contact to livestock reflects a different level of exposure to endotoxin and that endotoxin protects against the development of hay fever and allergic asthma. We plan to study 300 farmers` children and 600 non-farmers` children (6- 10 years old) in a collaborative investigation between Munich, Basel and Salzburg. Parents of the selected children will be asked to answer a questionnaire on allergic diseases and living condition of the child. Blood samples will be taken for measurement of specific IgE-antibodies to seven local allergens and for cell stimulation tests with LPS (lipopolysaccharides) + SEB (staphylococcus enterotoxin B). Further, it is aimed to measure the antibody response to various strains of endotoxin in the serum of the children. Finally, dust samples will be collected at different places of the child`s environment and endotoxin, Der p 1, Der f 1, Fel d I and Lol I concentrations measured. The results of this study could shed new light into the mechanisms of the rapid increase in allergic diseases in children and open doors for a potential primary prevention.

In an earlier survey in 1998 we found that children who had been growing up on a farm were three times less likely to develop asthma or hay fever when compared to their peers from the same rural environment. The aim of the present study was to assess potential causal factors for the decreased prevalence of allergic diseases in farmers` children. We asked parents of 2600 children,6-13 years old, to answer a standardised questionnaire on allergic diseases and environmental factors. In 1000 of these children we measured specific serum IgE antibodies to common allergens as well as allergens and endotoxin in the housedust. Exposure to stables and farm milk consumption in the first year of life turned out to be the strongest protective factors for the development of allergies. Children who were not exposed to these protectors were 10 times more likely to develop asthma and four times more likely to get hay fever. Endotoxin in dust of the living room and the child`s mattress was significantly increased in farmer`s children. Cats and dogs contributed substantially to the level of endotoxin. We speculate that early and regular contact to bacterial components like endotoxin might stimulate the developing immune system of growing children and by this mechanism protect against the development of allergic diseases. Our findings have the potential to serve as a model for the increasing prevalence of allergies in the western industrialised society. Further, they could help develop effective primary prevention strategies.