Tinea corporis caused by Trichophyton equinum in a rider and review of the literature

[Trichophyton equinum meets Chanel]

The horse is the most common reservoir of Trichophyton (T.) equinum. However, this zoophilic dermatophyte only rarely causes infections in humans. The following case report describes such a case. In addition to epidemiology, treatment is described and the morphological and physiological characteristics of T. equinum are illustrated. Because of its formation of spiral hyphae and nodal organs, which has not been previously documented for this species, the isolated strain was deposited in the German Collection of Microorganisms and Cell Cultures (DSM No. 114196).

[Zoophilic dermatophytes during coronavirus pandemic in Germany]

During the coronavirus pandemic, significantly more pets were probably bought and kept. This study focuses on whether more zoophilic dermatophytes have subsequently been isolated and which species predominate. In the 1‑year period from March 2020 through February 2021, all zoophilic dermatophytes from all submissions to the Mölbis laboratory were recorded. Both the cultural and the molecular evidence of fungal detection from skin scrapings, hair roots, and, in single cases, from nails, were considered. For dermatophyte DNA (Deoxyribonucleic acid) detection, an in-house polymerase chain reaction (PCR) - enzyme-linked immunosorbent assay (ELISA) was used. In distinct cases, identification of dermatophytes was confirmed by sequencing of the internal transcribed spacer (ITS) region of the rDNA, and of the gene of the translation elongation factor (TEF)-1α. In 579 (2.56%) of 22,575 samples studied in the year 2020/2021, zoophilic dermatophytes were detectable with PCR-ELISA and/or by cultivation. In comparison, the proportion of zoophilic dermatophytes was 2.03% in the 1‑year period 2014/2015, and only 1.6% in 2018/2019. The 579 zoophilic dermatophytes were identified as follows: Trichophyton (T.) benhamiae 186 (32.1%), T. mentagrophytes 173 (29.9%), T. quinckeanum 110 (19.0%), Microsporum (M.) canis 78 (13.5%), T. verrucosum 22 (3.8%), Nannizzia (N.) persicolor 8 (1.4%), T. erinacei 1 (0.2%), and T. equinum 1 (0.2%). T. benhamiae had the highest prevalence from June to September 2020, then again in December. T. quinckeanum is associated with a sharp increase in the mice population in Germany in 2020; a significant increase was found in the months September 2020 to January 2021. T. mentagrophytes had a conspicuous peak in September. Compered with that M. canis in November. Up to 50% of the dermatophytoses caused by T. mentagrophytes, T. quinckeanum, and M. canis affected children and adolescents, while in the case of T. benhamiae it was as much as two thirds. Tinea corporis was the most common, followed by tinea faciei and tinea capitis. M. canis infections affected the capillitium more frequently than the face. Zoophilic dermatophytes were increasingly isolated during the coronavirus pandemic in Germany when compared to previous year periods. In first place, the dermatophyte T. benhamiae from guinea pigs was found in children and adolescents. A significant proportion of dermatophytoses concerned adults. T. quinckeanum is an emerging pathogen in Germany with unprecedented high infection rates in 2020.

Concurrent Chorioptic Mange and Dermatophytosis in Dairy Goats: A Case Report

A concurrent chorioptic mange and dermatophytosis outbreak occurred in a goat flock in northwestern Italy. Sanitation of the flock was obtained following pour-on eprinomectin application at a dose of 1 mg/kg; enilconazole was used for environmental disinfection against dermatophyte spores.

Current Topics in Dermatophyte Classification and Clinical Diagnosis

Dermatophytes are highly infectious fungi that cause superficial infections in keratinized tissues in humans and animals. This group of fungi is defined by their ability to digest keratin and encompasses a wide range of species. Classification of many of these species has recently changed due to genetic analysis, potentially affecting clinical diagnosis and disease management. In this review, we discuss dermatophyte classification including name changes for medically important species, current and potential diagnostic techniques for detecting dermatophytes, and an in-depth review of Microsporum canis, a prevalent zoonotic dermatophyte. Fungal culture is still considered the “gold standard” for diagnosing dermatophytosis; however, modern molecular assays have overcome the main disadvantages of culture, allowing for tandem use with cultures. Further investigation into novel molecular assays for dermatophytosis is critical, especially for high-density populations where rapid diagnosis is essential for outbreak prevention. A frequently encountered dermatophyte in clinical settings is M. canis, which causes dermatophytosis in humans and cats. M. canis is adapting to its primary host (cats) as one of its mating types (MAT1-2) appears to be going extinct, leading to a loss of sexual reproduction. Investigating M. canis strains around the world can help elucidate the evolutionary trajectory of this fungi.

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

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.

Human and Zoonotic Dermatophytoses: Epidemiological Aspects

Introduction

Dermatophytes are a group of molds characterized by the ability to produce keratinases, thereby carving out for themselves specific ecological niches. Their traditional division into three genera, Trichophyton, Microsporum, and Epidermophyton has been expanded to nine and the species in each genus were modified. Dermatophytes are among the most prevalent causes of human and animal mycoses. Their epidemiology is influenced by various factors. These factors may be evolutive such as the predilected environment of the fungus, namely, humans (anthropophilic), animals (zoophilic), or environment (geophilic), is evolutionary and thus may require centuries to develop. Many other factors, however, result from a variety of causes, affecting the epidemiology of dermatophytoses within a shorter time frame.

Objective

This review aims at summarizing the factors that have modified the epidemiology of dermatophytoses during the last decades.

Results

Geographic and climatic conditions, demography such as age and gender, migration, socio-economic conditions, lifestyle, and the environment have had an impact on changes in the epidemiology of dermatophytoses, as have changes in the pattern of human interaction with animals, including pets, farm, and wild animals. A typical example of such changes is the increased prevalence of Trichophyton tonsurans, which spread from Latin America to the United States and subsequently becoming a frequent etiological agent of tinea capitis in Africa, Middle East, and other areas.

Conclusion

The comprehension of the epidemiology of dermatophytoses has a major bearing on their prevention and treatment. Since it is undergoing continuous changes, periodic assessments of the most recent developments of this topic are required. This article aims at providing such an overview.

Tinea corporis: an updated review

Background

Tinea corporis is a common fungal infection that mimics many other annular lesions. Physicians must familiarize themselves with this condition and its treatment.

Objective

This article aimed to provide a narrative updated review on the evaluation, diagnosis, and treatment of tinea corporis.

Methods

A PubMed search was performed with Clinical Queries using the key term ‘tinea corporis.’ The search strategy included clinical trials, meta-analyses, randomized controlled trials, observational studies, and reviews. The search was restricted to the English language. The information retrieved from the mentioned search was used in the compilation of the present article.

Results

Tinea corporis typically presents as a well-demarcated, sharply circumscribed, oval or circular, mildly erythematous, scaly patch or plaque with a raised leading edge. Mild pruritus is common. The diagnosis is often clinical but can be difficult with prior use of medications, such as calcineurin inhibitors or corticosteroids. Dermoscopy is a useful and non-invasive diagnostic tool. If necessary, the diagnosis can be confirmed by microscopic examination of potassium hydroxide wet-mount preparations of skin scrapings from the active border of the lesion. Fungal culture is the gold standard to diagnose dermatophytosis especially if the diagnosis is in doubt and results of other tests are inconclusive or the infection is widespread, severe, or resistant to treatment. The standard treatment of tinea corporis is with topical antifungals. Systemic antifungal treatment is indicated if the lesion is multiple, extensive, deep, recurrent, chronic, or unresponsive to topical antifungal treatment, or if the patient is immunodeficient.

Conclusion

The diagnosis of tinea corporis is usually clinical and should pose no problem to the physician provided the lesion is typical. However, many clinical variants of tinea corporis exist, rendering the diagnosis difficult especially with prior use of medications, such as calcineurin inhibitors or corticosteroids. As such, physicians must be familiar with this condition so that an accurate diagnosis can be made and appropriate treatment initiated.

Tinea corporis caused by Trichophyton equinum transmitted from asymptomatic dogs to two siblings

Each year, millions of people worldwide are affected by superficial mycoses, which are frequently caused by dermatophytes having affinity to the scalp, nails, hair and the stratum corneum of the skin. The changing reservoirs of zoophilic dermatophytes, the numerous reports of animal carrier status, and the increasing number of pets make the diagnosis difficult, which is usually impossible based only on medical history. Herein we present a case report of tinea corporis caused by Trichophyton equinum in siblings who had no contact with horses. The routine laboratory diagnostic procedures for identification of isolates were based on phenotypic and genotypic characteristics, especially molecular techniques using rDNA internal transcribed spacer sequences. The results showed that both techniques proved to be insufficiently discriminatory to differentiate two closely related species, i.e. Trichophyton equinum and Trichophyton tonsurans. Introduction of a TEF1 sequence analysis to the diagnostic procedures revealed consistent differences between these two species and facilitated unambiguous identification. Interestingly, dogs that could leave the homestead freely were the source of the infection in children. In conclusion, Trichophyton equinum was considered in the past as a strict zoophilic dermatophyte associated with horses and rarely transmitted to humans. This study revealed that this species can have other reservoirs and live in the fur of asymptomatic animals.

She Loves Me, She Loves Me Not: On the Dualistic Asexual/Sexual Nature of Dermatophyte Fungi

Dermatophytes are ascomycetous fungi whose sexuality is greatly influenced by their ecology. Sexual reproduction is ubiquitous among soil-related geophiles and some animal-associated zoophiles. In contrast, anthropophiles are generally present as a single mating type in the population and appear to reproduce asexually. In this article, the current knowledge on the sexuality of dermatophytes including reproduction modes, mating conditions, mating type distributions and the mating type (MAT) locus is presented in the context of revised taxonomy and discussed from an evolutionary perspective.

Polyphasic Discrimination of Trichophyton tonsurans and T. equinum from Humans and Horses

The anthropophilic dermatophyte Trichophyton tonsurans and its zoophilic counterpart T. equinum are phylogenetically closely related. The barcoding marker rDNA internal transcribed spacer (ITS) shows limited variation between these two species. In the current study, we combined molecular approaches with phenotypic data to determine the species boundaries between T. tonsurans (n = 52) and T. equinum (n = 15) strains originating from humans (n = 40), horses (n = 26), and a mouse (n = 1). Culture characteristics and physiology on Trichophyton agar media 1 and 5 were evaluated. Multi-locus sequencing involving ITS, partial large rDNA subunit (LSU), β-tubulin (TUB), 60S ribosomal protein (RPB), and translation elongation factor-3 (TEF3) genes, and the mating-type (MAT) locus was performed. Amplified fragment length polymorphism data were added. None of the test results showed complete mutual correspondence. With the exception of strains from New Zealand, strains of equine origin required niacin for growth, whereas most strains from human origin did not show this dependence. It is concluded that T. tonsurans and T. equinum incompletely diverged from a common lineage relatively recently. MAT1-1 and MAT1-2 are the main distinguishing genes between the two species.