Microbiome environment drives a dairy farmer’s health

According to a study led by the Marshfield Clinic Research Institute, central Wisconsin dairy farmers share many of the same microscopic organisms as their cows, that may lead to greater protection against illnesses like allergic rhinitis, asthma, eczema and diarrheal diseases.

Marshfield Clinic Health System researchers collaborated with the Washington University School of Medicine, to publish one of the largest studies of its kind in the April issue of Nature Microbiology, on the health of dairy workers, from occupational exposure to cow and manure-related microbiome.

Microbiome is the collection of all microbes, such as bacteria, fungi, viruses and their genes, that naturally live in the human body or an environment.

The published study, “Longitudinal dynamics of farmer and livestock nasal, and fecal microbiome and resistomes,” shows that farming is associated with microbiomes containing livestock-associated microbes. This is most apparent in the nasal bacterial community, with farmers harboring a richer and more diverse nasal community, than non-farmers.

Similarly, in the gut microbial communities, researchers identified more shared microbial lineages between cows and farmers from the same farms. Additionally, they found that shared microbes are associated with antibiotic resistance genes.

“Overall, our study demonstrates the interconnectedness of human and animal microbiomes,” said Sanjay Shukla, Ph.D. “It is increasingly evident that billions of microbes that inhabit the human gut, which includes the stomach, intestines and colon, have tremendous opportunity to influence the health of a person.”

Globally, half a billion people are employed in animal agriculture and are directly exposed to associated microorganisms. The extent to which such exposures affect resident human microbiomes is unclear.

The goal of the study was to investigate the effect of dairy microbiome environment on the gastrointestinal and flu-like related health issues of dairy farmers.

Researchers conducted a longitudinal profiling of the nasal and fecal microbiomes of 66 dairy farmers, and 166 dairy cows from 37 central Wisconsin dairy farms, ranging in size from 24 to 1,700 milking cows, over a year-long period. The farmers’ microbiomes were compared to matched healthy human subject controls from the same zip codes, whom researchers collected their stool and nasal swab samples every three months, over a threeyear period.

This in-depth study showed that the farmer nasal microbiome, although distinct, was very similar to the nasal microbiome of cows, but very different from the non-farmer control subjects. Also, there was a shared microbiome architecture between the cows and the farmers, even from different dairy farms, suggesting selection of a unique microbiota in dairy environments.

The sharing of the microbes in nasal passages was from the occupational exposure of the dairy environment. Not surprisingly, there was a higher sharing of bacterial lineages within in a farm between the dairy farmers and cows, than a different farm, suggesting the effect of cohabitation and the livestock driving the sharing.

Dairy farmers’ nasal microbiome samples were enriched with bacteria belonging to families Lactobacillaceae, Aerococcaceae and Enterococcaceae, which are known to provide a barrier to sinus infections.

The effect on the gut microbiome was different. The study showed selection of a host-driven gut microbiome in cows vs. humans. A cow’s gut microbiome was much more diverse than the dairy farmers and non-farmers, reflecting more of the host specific effect.

The study also showed the presence of a high number of antibiotic resistant genes in both cow’s and farmer’s, and nonfarmer’s gut, but the data suggests that dairy farming occupation had little effect on the restructuring of the farmer’s gut resistomes. A resistome is a collection of microbial genes that resists antibiotics, posing challenges in treating infections. Understanding the resistome is important in the battle against antibiotic resistance.

The study, naturally, led the researchers to pose additional questions that must be answered, including how occupational exposures interact with other environmental factors to shape farmer microbiomes.

“Future studies are warranted to determine whether and how, diet and antibiotics facilitate the acquisition, maintenance or amplification, of farm and livestockassociated microbes, as well as their antibiotic resistance genes,” said Shukla. “Ultimately, such a comprehensive understanding of how human-animal interfaces shape the resident human microbiomes, could give rise to novel strategies for mitigating the risks of animal agriculture on farmers and broader public health.”