The study comes from the University of Alberta and the basis is alterations to gut immunity and the microbiome. The microbiome refers to the mix of microorganisms in a given space (in this case the human gut). Various research strands point to the balance between different species, especially so-termed beneficial bacteria, as having a major influence upon human health and disease.
The finding is based on an analysis of fecal samples collected from infants. The samples were assessed as part of a major project called the Canadian Healthy Infant Longitudinal Development study, which has been running for over 20 years. The samples were studied by Dr. Anita Kozyrskyj. The line of inquiry was to understand why children who grow up in homes that have dogs have lower rates of asthma.
The reason for the lower asthma rates, which indicates a lower response to allergens, fits in with the hygiene hypothesis. This theory is based on exposure to dirt and bacteria early in life (such as from dog or cat fur and paws) leads to a higher level of immunity at an early age.
With the new research, although there is a benefit from keeping pets, the window of time where this makes a positive contribution is fairly narrow. This means that the effects are greatest if a baby is brought up in a home that already has pets. This is based on tracking the microbial composition of babies three months after birth and then later as infants. It seems that homes with pets leads to infants having a higher level of two bacteria: Ruminococcus and Oscillospira, compared with infants who are raised in homes without pets. The two microbes are linked with reduced childhood allergies and lower rates of obesity.
According to Dr. Kozyrskyj: “The abundance of these two bacteria were increased twofold when there was a pet in the house.” Some of the transfer of the organisms comes directly from the pet and the other part via the mother, including some organisms transferred through the birth process (be that C-section or vaginal delivery).
The research is published in the journal Microbiome, in a paper titled “Exposure to household furry pets influences the gut microbiota of infant at 3–4 months following various birth scenarios.”
