Many people decide to become dog owners for reasons such as companionship, protection of one’s home, or simply the happiness that is felt every day from being greeted by a furry friend. To add to this list, owning a dog might also change the microbial composition in your gut and alleviate the symptoms of allergies.
Researchers have found that dogs contribute to an increased diversity of bacteria in house dust and exposure to this house dust dampens the allergic response to several allergens such as ovalbumin (a protein in egg whites) and cockroach allergens.
To test this, mice were fed either dog-associated house dust, or house dust from a home with no dogs. The mice that were fed the dog house dust showed significant reduction in airway immune cells, serum immunoglobulin E (IgE), and a decrease in airway responses compared to mice that were fed house dust from a home that did not have dogs. Overactive airway immune responses and high levels of serum IgE early in life are commonly associated with development of childhood allergic diseases. Therefore, exposure to dogs during infancy may reduce the risk of developing diseases such as asthma and atopic dermatitis.
Guts of the “protected” mice were examined by generating a microbiome profile using a phylogenetic microarray. Phylogenetic microarrays evaluate the bacterial community composition based on the presence or absence of microbial genes in a sample. From this, researchers were able to determine if the microbiota composition differed between the groups of treated mice. The genera Lactobacillus, and particularly Lactobacillus johnsonii, were highly enriched in mice which had been fed dog house dust.
Lactobacillus johnsonii is known to reside in the human intestine and is part of the complex of Lactobacillus species that are associated with probiotic activities. In the same study, mice were supplemented with Lactobacillus johnsonii and produced similar results to the mice that were fed dog house dust. They exhibited a diminished airway response to allergens and further, did not show airway hyperresponsiveness when infected with respiratory synctial virus (RSV). RSV infections during infancy can lead to complications and are the leading cause of childhood hospitalizations as well as a risk factor for developing childhood asthma. The findings from this study can lead to development of probiotics for infants that could reduce the risk of developing allergic conditions.
There is still a lack of evidence to suggest that the putative probiotic did in fact originate from the house dust. Further studies will focus on identifying the organisms in the dust samples and determining if the dust microbes are themselves playing a role in airway protection or if components in the dust (such as allergens) are changing the composition of the already existing microbiota and if these beneficial effects can also be witnessed in humans. In the meantime, dog owners may just have a good enough reason to dust their houses a little less often.
Written by Alani Barajas
Alani Barajas is a Research and Development Technician at Hardy Diagnostics. She earned her bachelor’s degree in Microbiology at Cal Poly, San Luis Obispo. During her studies at Cal Poly, much of her time was spent as part of the undergraduate research team for the Cal Poly Dairy Products Technology Center studying spore-forming bacteria in dairy products. Currently she is working on new chromogenic media formulations for Hardy Diagnostics, both in the prepared and powdered forms.