Healthy Cats May Have a Richer Skin Microbiome Than Allergic Cats

A beautiful coat on a healthy cat can be irresistible, but when a cat suffers from skin issues such as allergic dermatitis it can be distressful to pet and owner alike. In new research comparing the skin of healthy cats to those with cutaneous disorders, a team of veterinary researchers has discovered that healthy cats have a richer diversity of fungal microbiota in their skin than cats with allergic skin conditions, shedding light on the role of a cat’s skin microbiome in the pathogenesis of skin diseases.

In their new study published in the journal Veterinary Dermatology, researchers from Texas A&M University and University of Minnesota discuss the distribution of bacterial and fungal microbiota, or mycobiota, across the body of both humans and canines. Studies using next generation sequencing (NGS) technology have revealed much about the microbiota of the skin of people and dogs, showing bacterial and fungal dysbiosis in human atopic dermatitis and canine allergic dermatitis. The researchers in this study note that little is known about the skin microbiota of cats with nonflea nonfood-induced hypersensitivity dermatitis (NFNFIHD), and their goal was to use NGS to investigate the mycobiota of cats with feline allergic skin diseases.

Allergic dermatitis in cats can occur from reactions to food, fleas, and environmental allergens. Reactions in the skin can include itching, red bumps, foul odor, and thinning or loss of hair. Cats who scratch or lick themselves frequently and show changes to their skin or coat may be experiencing an allergy.

Enrolled in the study’s healthy group were eleven cats with no prior dermatological conditions; five neutered males and six spayed females ranging in age from 2 to 17 years. Nine cats with hypersensitivity dermatitis made up the allergic group, including four neutered males and five spayed females ranging in age from 4 to 11 years. Of the 20 cats enrolled in the study, 13 lived entirely indoors. In the allergic group, the most common symptoms were pruritus and alopecia. The researchers examined sites around the bodies of each cat, taking samples with sterile skin swabs from the axilla, ear canal, dorsum, groin, interdigital space, and nostril areas. They collected 132 samples from the healthy cats and 54 from the allergic cats and analyzed them using a desktop genetic sequencer, looking for both alpha diversity (mycobiota diversity within a sample) and beta diversity (mycobiota diversity between samples).

Of the fungal phylums found in the cats, Ascomycota made up almost 80 percent of the fungal sequences in both the healthy cats and allergic cats. Of those, Dothideomycetes was the most abundant class, accounting for nearly half of the sequences in healthy cats and more than a third in the allergic cats. The researchers noted that the conjunctiva and reproductive tract sites of healthy cats were the least diverse body sites, whereas the preaural space was the richest and most diverse. Mucosal sites including conjunctiva, nostril, and reproductive tract sites were significantly less diverse than oral, sebaceous (chin), and haired sites.

When the researchers compared their findings from the healthy and allergic cat groups, estimated alpha diversities and beta diversities were not significantly different between groups. Within their analysis though, the researchers found that nine taxa were significantly more abundant in the healthy group, whereas the two classes Agaricomycetes and Sordariomycetes were significantly more abundant in the allergic group. In comparing the presence of shared fungal taxa between samples, the axilla and the interdigital space showed the most significant difference between the healthy and allergic groups.

With these initial findings, many questions remain for the researchers in the study on the role of grooming habits, environmental conditions, and other factors that may influence mycobiota diversity and distribution in cats.