Why Amish children so rarely get asthma: the clue is in their dust

    9 August 2016

    Microbes from farm animals could be used to inoculate children against asthma, according to research published in the New England Journal of Medicine.

    The ‘hygiene hypothesis’ suggests that the condition is becoming more common in children because the environments they live in are too clean, and this study backs up the claim.

    Scientists at the University of Chicago had noticed a stark difference in asthma rates between two American farming communities, the Amish of Indiana and the Hutterites of North Dakota. Only between two and four per cent of Amish children have asthma, compared with 15 to 20 per cent of Hutterite children.

    They found that the difference could be explained by the fact that Amish children grow up in close proximity to barn animals, whereas Hutterite farms are more industrialised and tend not to be attached to the home, reducing the opportunity for exposure. In other ways the two communities live in similar environments.

    The new research suggests that children exposed to microbes that stimulate their immune systems during infancy will be protected against asthma.

    The 30 Amish children involved in the study all had a large proportion of neutrophils — infection-fighting white blood cells. The researchers found that the neutrophils were young, which was evidence that their bodies were regularly reacting to microbial invaders. The Hutterite children studied had far fewer and older neutrophils in their blood.

    Researchers also analysed dust in Amish and Hutterite homes and found a vastly different microbial composition. They then administered the dust to mice. The Amish dust appeared to protect the mice from allergic reactions.

    Dr Talal Chatila, of the University of Harvard, said in an editorial accompanying the research: ‘This is an exciting paper. It is not far-fetched to start thinking of how one could harness those bacteria for a therapeutic intervention.’

    He added that he was not suggesting that people start selling Amish dust to protect children from asthma. ‘But I wouldn’t be surprised if inactive forms of the bacteria could be used.’

    Instant analysis
    The prevalence of asthma and other allergic conditions has greatly increased over the last decades. The reasons for this are becoming clearer, and this paper elucidates them further.

    The authors compared the children of two isolated religious sects in rural North America, the Amish and the Hutterites. One in 20 of the former, and one in four of the latter, suffer from asthma. What is the reason for this enormous difference?

    The Amish still use traditional farming methods while the Hutterites have gone over to modern methods, including the use of pesticides and fungicides. The authors excluded relevant genetic differences between the two groups and found that the homes of the Amish contained many times more allergens than those of the Hutterites.

    It seems, then (what has been suspected before), that early childhood exposure to allergens protects against the development of allergy. Our problem is that we are too clean.
    Research score: 4/5