The Impact of Prenatal Dog Keeping on Infant Gut Microbiota Development

Numerous studies have demonstrated the association between early exposure to indoor pets and lower risk of atopic conditions. Alteration of the early gut microbiome is a potential link between pet exposure and disease risk. The purpose of this study is to examine the effects of prenatal and early-life dog exposure on the development of the infant gut microbiome.The study included mother-child pairs from southeastern Michigan enrolled in the MAAP birth cohort. Inclusion criteria required either regular exposure to an indoor dog or living in a pet-free home.Mothers completed a series of questionnaires during the study period regarding their infant’s health, diet, and pertinent exposures. Infant and maternal stool samples were collected at 1 week, 1 month, 3 months, 6 months, and 18 months. Of infants, 131 provided at least 1 stool sample that was successfully sequenced. Bacterial DNA was extracted from samples using 16S ribosomal RNA sequencing, then sorted into operational taxonomic units.There were 141 mother-child pairs included in this study. The infant microbiota resembled the maternal vaginal and rectal microbiome at birth and became more similar to maternal gut microbiota with age. Dog exposure was associated with significantly greater alpha-diversity (number of taxa and relative abundance) of infants’ microbiomes when averaged across all ages and adjusted for race and delivery mode. This effect was strongest at 3 and 6 months but had diminished by 18 months. Dog exposure significantly increased beta-diversity (identity of taxa observed) only in formula-fed infants.Early dog exposure was associated with a statistically significant increase in infant gut microbial diversity at 3 months and 6 months. Dog-exposed, formula-fed infants had a statistically significant increase in certain bacteria that have been previously linked to increased anti-inflammatory factors. These data support gut microbiome alterations as a potential link between dogs and lower risk of atopy, inviting further investigation.No causal mechanism between early dog exposure and reduction in atopy risk has been identified. This is the first longitudinal controlled study evaluating a potential association between early dog exposure and changes in the infant gut microbiome. Additional studies with larger sample sizes are needed to validate these findings. Further investigation of the proposed anti-inflammatory properties of select gut microbiota and the relationship with allergic and inflammatory conditions is warranted.