Horse owners know the list of potential triggers for recurrent airway obstruction (RAO or heaves) well—an unclean environment, lack of fresh air, dusty hay, and more. But could we soon add microbiomes, or microbial communities, in the airway to that list? A team of researchers from Canada recently took a look to find out.

A microbiome is, essentially, the different microbial "communities" living on or in different sites of an organism’s body. Scientists believe that microbiomes in the airways could play a role in chronic inflammatory disease development, so Julia Montgomery, DVM, PhD, Dipl. ACVIM, and colleagues studied whether microbiomes could play a role in equine recurrent airway obstruction (RAO or heaves).

Montgomery, an assistant professor of large animal medicine at the University of Saskatchewan’s Western College of Veterinary Medicine, presented the team’s results at the 2015 American College of Veterinary Internal Medicine Forum, held June 4-6 in Indianapolis, Indiana. Katharina Lohmann, MedVet, PhD, Dipl. ACVIM, an associate professor of large animal medicine, and Janet Hill, BSc (Hon), PhD, associate professor and graduate chair of veterinary microbiology—both from the Western College of Veterinary Medicine—worked with Montgomery on the study.

In their pilot study, the team evaluated the tracheal microbiomes—the microbial communities residing in the horse’s trachea—of three healthy horses and five with heaves (two with active disease at the time of sampling and three in remission) on two occasions, about two weeks apart. They collected tracheal aspirates and determined the total genomic DNA included in those samples. Specifically, the team estimated the samples’ total bacterial load using quantitative polymerase chain reaction testing; then they organized the DNA sequences they found into operational taxonomic units (OTUs). Essentially, researchers use OTUs to classify microbial communities at the phylum level (the second-largest standard unit of biological classification) and to identify “nearest neighbors” based on known sequences at the species level