Meason-Smith C, Diesel A, Rodriguez Hoffman A, et al. Characterization of the cutaneous mycobiota in healthy and allergic cats using next generation sequencing. Vet Dermatol. 2016 Aug 23. (Winn funded study)
Studies have indicated that newer methodologies such as next generation sequencing (NGS) have characterized host-associated microbial communities (microbiota) in more detail and this had led to evidence that a more diverse microbiota is in existence than previously thought. In humans, skin-associated bacterial microbiota are distributed according to physiological niches (dry, moist, and sebaceous microenvironments), yet the distribution of the fungal microbiota (mycobiota) is more dependent upon body site location. In dogs, on the other hand, the bacterial microbiota of canine skin are influenced by body site location. The mycobiota are more likely to be distributed evenly across body sites within a dog and significant differences in mycobiota are observed between dogs. Until this current study, the skin of cats had not been examined using NGS.
The investigators in this study hypothesized that the fungal microbiota (mycobiota) would be similar to that of dogs, include a predominance of environmental fungi, and that fungal dysbiosis would be present on the skin of allergic cats. The study included eleven healthy cats and nine cats diagnosed with one or more cutaneous hypersensitivity disorders (to include flea bite, food-induced and nonflea nonfood-induced hypersensitivity). Healthy cats were sampled at twelve body sites (axilla, chin, conjunctiva, dorsal nose, dorsum, ear canal, groin, interdigital space, nostril, oral cavity, preaural space and vulva or prepuce) and allergic cats at six sites (axilla, dorsum, ear canal, groin, interdigital space, and nostril).
Cats are reported to suffer from a poorly understood allergic dermatitis often resembling human and canine allergic dermatitis. This condition is known as nonflea nonfood-induced hypersensitivity dermatitis (NFNFIHD) that the authors believe suggests that environmental allergens are the triggers for these cases.
The results from the fungal sequences showed the most abundant from the skin of all cats were classified as Cladosporium and Alternaria. The sites with the fewest number of fungi were the mucosal sites, including nostril, conjunctiva and reproductive tracts). The pre-aural space had the most. In analyzing the allergic feline skin, there were significantly greater amounts of Agaricomycetes and Sordariomycetes present, and significantly less Epicoccum compared to healthy feline skin.
The study additionally demonstrated that fungi colonizing the skin of cats tend to be similar across the entire body of the cat. Differences are observed between cats. The authors comment that grooming habits of cats may influence the dissemination of mycobiota across the entire body. Yet, unlike in dogs with allergic dermatitis, there was not an overall reduction in fungal diversity in the allergic cat group.
One other interesting note was that one cat was diagnosed with dermatophytosis a few months prior to collection of the samples. The skin lesions resolved on this cat with application of lime sulfur dips and no clinical lesions were noted at the time of sampling. Samples from this cat revealed significantly higher amounts of the fungus, Arthroderma, which is the sexual state of Microsporum (one cause of dermatophytosis). This raises a question by the authors if dermatophytosis could have a long-standing effect on the skin mycobiota of the entire cat. Also, it raises concern about a potential carrier state in the absence of clinical signs. (VT)
Favrot C, Steffan J, Seewald W, et al. Establishment of diagnostic criteria for feline nonflea-induced hypersensitivity dermatitis. Vet Dermatol. 2012 Feb; 23 (1):45-50.