Generalized dermatophytosis caused by Trichophyton equinum in 8 juvenile black bears in California

Abstract

From 2014–2019, 8 juvenile black bears ( Ursus americanus) from different geographic regions were presented to the California Department of Fish and Wildlife because of emaciation, alopecia, and exfoliative dermatitis that resulted in death or euthanasia. Autopsy and histopathology revealed that all 8 bears had generalized hyperkeratotic dermatitis, folliculitis, and furunculosis. Skin structures were heavily colonized by fungal hyphae and arthrospores; fungal cultures of skin from 7 bears yielded Trichophyton equinum, a zoophilic dermatophyte reported only rarely in non-equid species. Additional skin conditions included mites (5), ticks (2), and coagulase-negative Staphylococcus sp. infections (2). No other causes of morbidity or mortality were identified. Molecular comparisons performed at the University of Texas Fungal Reference Laboratory determined that all isolates produced identical banding patterns, potentially representing a clonal population. Dermatophytosis is commonly localized and limited to the stratum corneum of the epidermis and hair follicles. Generalized disease with dermal involvement is rare in immunocompetent individuals; illness, malnutrition, age, or immunosuppression may increase susceptibility. Underlying causes for the severe disease impact in these bears were not evident after physical or postmortem examination. The mechanism by which bears from different geographic locations had severe, T. equinum–associated dermatophytosis from a potentially clonal dermatophyte could not be explained and warrants further investigation.

Diagnosis and treatment of dermatophytic furunculosis in a polar bear (Ursus maritimus)

“…Underlying immunosuppression or susceptibility to dermatophytosis infection were not identified. 9 The polar bear in this case report was a sub-adult male in a well-kept environment, healthy body condition and good general health.…”

“…7 Dermatophytosis has been described in a small number of bears in the literature. 8,9 M. gypseum was diagnosed in a pet bear (species unknown) and successfully treated with topical iodine. 8 Generalised dermatophytosis with dermal involvement, due to infection with Trichophyton equinum, was described in eight captive juvenile black bears from different locations in California.…”

“…Dermatophytosis has been described in a small number of bears in the literature 8,9 . M. gypseum was diagnosed in a pet bear (species unknown) and successfully treated with topical iodine 8 .…”

Disseminated dermatophytosis and acquired immunodeficiency syndrome:literature review and presentation of clinical experience

“…Adhered to human keratinocytes, the dermatophytes penetrate in the stratum corneum (20) .This process can be facilitated by a change in the structure or environment of the stratum corneum (humidity, trauma), which, together with the environment of the follicular ostium, provide nutrition and proper pH for the dermatophyte to grow. A series of substances that are locally produced by the hosts, such as β-defensins, unsaturated transferrin from sweat and fat, besides long chain unsaturated fatty acids produced by sebaceous glands, inhibit the growth of dermatophytes on the epidermis (21) .…”