Farm effect bacteria tied to lower childhood asthma risk in study
A European study links specific barn-air bacteria to lower asthma and allergy risk, tracing a possible immune pathway in children.
By Priya Raghavan · Science Reporter
3 min read
Researchers have identified farm effect bacteria that may help explain why children raised around barns are less likely to develop asthma and allergies. The study, published in NEJM Evidence, matters because it moves the long-running “farm effect” idea from broad exposure to named microbes and biological pathways.
The international team was led by Professor Markus Ege of the Dr. von Hauner Children’s Hospital at LMU University Hospital and the Institute of Asthma and Allergy Prevention at Helmholtz Munich. According to LMU Klinikum München, the work identifies specific bacteria in barn air, the substances associated with them and the human receptors that may help produce protection.
The farm effect refers to the lower rates of asthma, hay fever and allergies seen in children who grow up in farm settings compared with classmates who do not. Earlier observational studies in several countries have linked farm environments with broader microbial exposure, but those studies could not by themselves prove which microbes were responsible.
Which bacteria are linked to the farm effect?
The researchers singled out a small group of Gram-positive bacteria, including Romboutsia timonensis and Glutamicibacter arilaitensis, according to Giulia Pagani, the study’s first author and a bioinformatician at Helmholtz Munich. The team reported that these bacteria together accounted for about two-thirds of the farm effect associated with asthma protection and about half of the effect seen for hay fever and atopic eczema.
LMU Klinikum München said the bacteria originate in cows’ digestive tracts and are found in barn air. The study connects them with compounds including kynurenine, xanthine, alpha-linolenic acid and stearidonic acid.
Those substances can be inhaled and recognized by receptors on airway cells, according to the researchers. The receptors named in the study are AhR and PPARγ, both of which have roles in immune activity and may help restrain excessive inflammatory reactions.
How did the researchers study children and barn dust?
The team analyzed data from more than 1,000 children enrolled in European rural studies. For each child, researchers had nasal swabs and mattress dust samples, and for 47 farm children they also had dust collected from cowsheds.
Scientists examined bacteria and fungi in the samples, compared how microbial groups related to one another and looked for links with asthma protection. The group used genetic and metabolic analyses along with computer modeling, then checked the findings against additional data from France and Finland, according to LMU Klinikum München.
The work also fits into the hygiene hypothesis, an idea first proposed in 1989 after rising rates of childhood allergies, asthma and hay fever in Western industrialized countries. That hypothesis holds that children exposed to too few microbes early in life may have immune systems more likely to overreact.
Ege said previous research had relied heavily on correlations, while the new study lays out more of the proposed chain from cows to barn air, bacterial products, airway receptors and lower inflammatory responses. The study does not report a treatment for children, but the researchers said the findings give laboratory scientists clearer targets for studying how the farm effect works.
According to LMU Klinikum München, that could support future efforts to develop a drug that imitates parts of the farm effect without requiring children to spend time in barns.
This story draws on original reporting from Medical Xpress.