Children living on farms are significantly less likely to develop asthma than their peers, a new study shows. The research was partially supported by two EU-funded projects: GABRIEL ('A multidisciplinary study to identify the genetic and environmental causes of asthma in the European Community') and PARSIFAL ('Prevention of allergy – risk factors for sensitization in children related to farming and anthroposophic life style'). GABRIEL was funded under the 'Life sciences, genomics and biotechnology for health' Thematic area of the Sixth Framework Programme (FP6) and PARSIFAL under the 'Quality of life and management of living resources' Programme of the EU's Fifth Framework Programme (FP5).
The incidence of asthma among children in Europe continues to rise. However, not all children are equally at risk, and several studies published over the past few years have shown that children living on farms will have a smaller chance of developing asthma compared to their peers. An international team of researchers has confirmed this finding in an epidemiological study published in the journal New England Journal of Medicine (NEJM). The study showed that the lower susceptibility of farm children to asthma is largely the result of their exposure to a greater variety of microorganisms compared with other children living in the same region.
Asthma is one of the most prevalent chronic illnesses affecting children in Europe; understanding its causes is important. In order to investigate why farm children should suffer less from this condition, researchers examined a group of schoolchildren from Bavaria in Germany and compared children living on farms with others from the same rural districts who had little direct contact with farms.
They focused their investigation on the microbes present in domestic interiors, collecting household dust from children's bedrooms, and analysing the bacterial and fungal DNAs (deoxyribonucleic acids) in the samples. The results showed that farm children must cope with a much greater range of microorganisms than children who live in other environments. According to the researchers, the bacteria and fungi seem to act as guardians of health and therefore the more diverse the microbial population, the lower the risk of asthma. Exactly how the cells and spores perform this trick remains unclear, but the team put forward a series of possible explanations.
'One possibility is that a particular combination of microbial species stimulates the innate immune system and so prevents it from entering a state that promotes the development of asthma,' suggests Dr Markus Ege from the Children's Surgical Clinic at Ludwig-Maximilians-Universität München (LMU Munich) in Germany. Alternatively, continuous exposure to many different microorganisms may make it more difficult for the species that potentially induce asthma to become the dominant forms in the lower respiratory tract, Dr Ege points out.
However, microbial diversity alone is not enough to prevent asthma. More probably, it takes a particular consortium of species to exert a protective effect, the researchers suggest.
'Within the large spectrum of organisms that we examined, there are some that may be of special interest,' Dr Ege comments. 'Among these are certain species of bacilli and staphylococci — Staphylococcus sciuri, for instance — as well as fungi of the genus Eurotium.'
The researchers plan to examine — at the level of single species — the nature of the link between the microorganisms in household dust and the protective effect, with the long-term goal of identifying candidates that might serve as the basis of a live vaccine against asthma. 'We have a long way to go before we can present new preventive measures, but at least we now have candidates for the development of a vaccine,' Dr Ege concludes.
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