Babies from families with pets – 70% of which were dogs – showed higher levels of two types of microbes associated with lower risks of allergic disease and obesity, found a University of Alberta study.
But don’t rush out to adopt a furry friend just yet. “There’s definitely a critical window of time when gut immunity and microbes co-develop, and when disruptions to the process result in changes to gut immunity,” said Dr Anita Kozyrskyj, a U of A paediatric epidemiologist and one of the world’s leading researchers on gut microbes – micro-organisms or bacteria that live in the digestive tracts of humans and animals.
The latest findings from Kozyrskyj and her team’s work on faecal samples collected from infants registered in the Canadian Healthy Infant Longitudinal Development study build on two decades of research that show children who grow up with dogs have lower rates of asthma.
The theory is that exposure to dirt and bacteria early in life – for example, in a dog’s fur and on its paws – can create early immunity, though researchers aren’t sure whether the effect occurs from bacteria on the furry friends or from human transfer by touching the pets, said Kozyrskyj.
Her team of 12, including study co-author and U of A post-doctoral fellow Hein Min Tun, take the science one step closer to understanding the connection by identifying that exposure to pets in the womb or up to three months after birth increases the abundance of two bacteria, Ruminococcus and Oscillospira, which have been linked with reduced childhood allergies and obesity, respectively.
“The abundance of these two bacteria were increased twofold when there was a pet in the house,” said Kozyrskyj, adding that the pet exposure was shown to affect the gut microbiome indirectly – from dog to mother to unborn baby – during pregnancy as well as during the first three months of the baby’s life. In other words, even if the dog had been given away for adoption just before the woman gave birth, the healthy microbiome exchange could still take place.
The study also showed that the immunity-boosting exchange occurred even in three birth scenarios known for reducing immunity, as shown in Kozyrskyj’s previous work: C-section versus vaginal delivery, antibiotics during birth and lack of breastfeeding.
What’s more, Kozyrskyj’s study suggested that the presence of pets in the house reduced the likelihood of the transmission of vaginal GBS (group B Strep) during birth, which causes pneumonia in newborns and is prevented by giving mothers antibiotics during delivery.
It’s far too early to predict how this finding will play out in the future, but Kozyrskyj doesn’t rule out the concept of a “dog in a pill” as a preventive tool for allergies and obesity.
“It’s not far-fetched that the pharmaceutical industry will try to create a supplement of these microbiomes, much like was done with probiotics,” she said.
Background: Early-life exposure to household pets has the capacity to reduce risk for overweight and allergic disease, especially following caesarean delivery. Since there is some evidence that pets also alter the gut microbial composition of infants, changes to the gut microbiome are putative pathways by which pet exposure can reduce these risks to health. To investigate the impact of pre- and postnatal pet exposure on infant gut microbiota following various birth scenarios, this study employed a large subsample of 746 infants from the Canadian Healthy Infant Longitudinal Development Study (CHILD) cohort, whose mothers were enrolled during pregnancy between 2009 and 2012. Participating mothers were asked to report on household pet ownership at recruitment during the second or third trimester and 3 months postpartum. Infant gut microbiota were profiled with 16S rRNA sequencing from faecal samples collected at the mean age of 3.3 months. Two categories of pet exposure (i) only during pregnancy and (ii) pre- and postnatally were compared to no pet exposure under different birth scenarios.
Results: Over half of studied infants were exposed to at least one furry pet in the prenatal and/or postnatal periods, of which 8% were exposed in pregnancy alone and 46.8% had exposure during both time periods. As a common effect in all birth scenarios, pre- and postnatal pet exposure enriched the abundance of Oscillospira and/or Ruminococcus (P < 0.05) with more than a twofold greater likelihood of high abundance. Among vaginally born infants with maternal intrapartum antibiotic prophylaxis exposure, Streptococcaceae were substantially and significantly reduced by pet exposure (P < 0.001, FDRp = 0.03), reflecting an 80% decreased likelihood of high abundance (OR 0.20, 95%CI, 0.06–0.70) for pet exposure during pregnancy alone and a 69% reduced likelihood (OR 0.31, 95%CI, 0.16–0.58) for exposure in the pre- and postnatal time periods. All of these associations were independent of maternal asthma/allergy status, siblingship, breastfeeding exclusivity and other home characteristics.
Conclusions: The impact of pet ownership varies under different birth scenarios; however, in common, exposure to pets increased the abundance of two bacteria, Ruminococcus and Oscillospira, which have been negatively associated with childhood atopy and obesity.
Hein M Tun, Theodore Konya, Tim K Takaro, Jeffrey R Brook, Radha Chari, Catherine J Field, David S Guttman, Allan B Becker, Piush J Mandhane, Stuart E Turvey, Padmaja Subbarao, Malcolm R Sears, James A Scott, Anita L Kozyrskyj