Prevalence of dermatophytosis in animals and antifungal susceptibility testing of isolated Trichophyton and Microsporum species

Global Dermatophyte Infections Linked to Human and Animal Health: A Scoping Review

Dermatophytes are commonly encountered pathogens in clinical practice causing superficial infections of the skin, hair, and nails. These pathogens are often found on animals such as livestock (e.g., cattle, rabbits) and pets (e.g., cats, hedgehogs) that can lead to spillover infections in human populations. Here, we reviewed published reports (2009-2024) of dermatophyte infections in animals and in humans with a history of animal contact. A literature search was completed in October 2024 using PubMed, Embase (Ovid), and Web of Science (Core Collection), which identified 250 articles. Generally, dermatophytes tend to infect younger animals with long hair and exhibit a species-specific host range. Microsporum canis was the most commonly reported species-linked to cats-that can cause tinea capitis, especially concerning the development of kerion in children. Trichophyton verrucosum is strongly associated with cattle. The Trichophyton mentagrophytes complex shows a diverse range of animal hosts, with rabbits being most frequently reported; however, T. mentagrophytes var. erinacei is almost exclusively isolated from hedgehogs, and T. mentagrophytes var. benhamiae is more commonly found on rodents (e.g., guinea pigs). Lastly, the geophilic Nannizia gypsea has been isolated from both dogs and cats. Managing dermatophyte zoonoses is an ongoing challenge, as healthcare providers may empirically treat with corticosteroids or antibacterial agents due to its atypical inflammatory appearance. Evidence of in vitro resistance against griseofulvin and fluconazole has been documented in multiple zoonotic dermatophyte species. Resistance development against terbinafine and itraconazole is also a possibility, although the number of reports is scarce. Under the principles of the One Health approach, research on human fungal diseases should take animal and environmental factors into account. A renewed call for increased testing efforts is warranted.

Drug-resistance genes and antifungal susceptibility of Trichophyton verrucosum variants isolated from bovine skin lesions and farm environments

Trichophyton verrucosum causes a highly contagious disease in bovines and is occasionally transmitted to humans. Azoles are widely used as antifungal drugs in bovines, and act by targeting the ergosterol biosynthesis pathway. However, cases of treatment failure and recurrence of dermatophyte infections have been associated with mutations at the drug target site. Currently, information on T. verrucosum variants is lacking. This study aimed to classify T. verrucosum variants isolated from animals exhibiting clinical symptoms and cattle environments in the Republic of Korea based on their antifungal susceptibility and the presence or absence of ergosterol biosynthesis (ERG) and subtilisin genes. Of 139 clinical and 39 environmental samples, 86 and 21 were found to be infected, respectively. The positivity rate of calves aged 1-6 months was 73.1%, which was significantly higher than that of calves aged >6 months (55.2%). Twenty-seven T. verrucosum strains were identified as T. album (n = 9), T. ochraceum (n = 6), and T. discoides (n = 12). Antifungal susceptibility testing showed that enilconazole had the lowest geometric mean antifungal activity of 1.08, 1, and 0.94 µg/ml against T. album, T. ochraceum, and T. discoides, respectively. The detection ratios of ERG3 and ERG6 differed significantly among the three variants. In conclusion, our study suggests conducting sample cultures and antifungal susceptibility tests on isolates before administering antifungal drugs. Moreover, the expression profile of ERG appears to have a potential link to drug susceptibility. This information may contribute to the prevention and management of dermatophytosis in cattle.

Dermatophytosis caused by Trichophyton benhamiae in a sea lion. First report

Fungal infections in marine animals, particularly pinnipeds, have seen a notable increase, often linked to compromised immune systems in captive environments. Trichophyton species, while common in terrestrial mammals, have sporadically caused dermatophytosis in pinnipeds. A South American sea lion (Otaria byronia) presented with Trichophyton benhamiae infection, marking the first such case in this species. Effective treatment combined oral terbinafine with topical ozonized oil, supported by silymarin for liver protection. Accurate fungal identification and sensitivity testing were key to the successful management and recovery of the patient.

Human and mouse TLR2 results in different activation of p38 and JNK signal pathway in HaCaT infected by Trichophyton rubrum and Microsporum canis

Introduction

It has long been recognized that inflammation to dermatophyte infection is different among various hosts, but the mechanism underlying is still not well understood. Toll-like receptor (TLR2), mediates the innate immune response against dermatophyte infection and is very important to trigger the inflammatory response to dermatophytes. Considering the different amino acid sequences and structures of TLR2, we speculated that TLR2 from different hosts will activate the downstream signal pathways to varying degrees, resulting in different inflammatory responses to dermatophytes.

Methods

In this study, we constructed the mice-human fusion TLR2 expressed HaCaT (mhTLR2-HaCaT) by replacing the extracellular ligand recognition region of human TLR2 with that of the mouse. Then hTLR2-HaCaT cells and mhTLR2-HaCaT cells were infected with T. rubrum and M. canis for 24 h followed by immunoblotting to asses associated proteins of p38 and JNK signal pathway.

Results

Compared with that of human TLR2 expressed HaCaT (hTLR2-HaCaT), levels of phosphorylated p38 protein were increased in mhTLR2-HaCaT cells stimulated by T. rubrum for 24 h, and levels of phosphorylatedJNK and c-Jun protein were increased in mhTLR2-HaCaT cells whenstimulated with M. canis for 24 h.

Discussion

Compared with hTLR2-HaCaT cells, p38 and JNK signal pathwayswere activated in mhTLR2-HaCaT after being infected by Trichophyton rubrumand Microsporum canis, respectively. Since p38 and JNK are the mainpathways that transduce the signal for host recognition of dermatophytes andmediate the downstream inflammatory response, it suggested that theinterspecific difference of TLR2 ectodomain may be one of the reasons for thedifferent inflammatory manifestations between humans and mice infected bythese two dermatophytes. Quite especially, the mouse-derived TLR2extracellular recognition region is more effective in recognizing T. rubrum andM. canis to activate the downstream signal pathways, resulting in a tenserinflammatory response against these two dermatophytes.

Emerging Fungal Infections: from the Fields to the Clinic, Resistant Aspergillus fumigatus and Dermatophyte Species: a One Health Perspective on an Urgent Public Health Problem

Purpose of Review

For this review, we use a One Health approach to examine two globally emerging public health threats related to antifungal drug resistance: triazole-resistant Aspergillus fumigatus infections, which can cause a life-threatening illness in immunocompromised hosts, and antifungal-resistant dermatophytosis, which is an aggressive skin infection caused by dermatophyte molds. We describe the state of current scientific knowledge and outline necessary public health actions to address each issue.

Recent Findings

Recent evidence has identified the agricultural use of triazole fungicides as an important driver of triazole-resistant A. fumigatus infections. Antifungal-resistant dermatophyte infections are likely driven by the inappropriate use of antifungal drugs and antibacterial and corticosteroid creams.

Summary

This review highlights the need for a One Health approach to address emerging antifungal resistant infections, emphasizing judicious antifungal use to preserve available treatments; strengthened laboratory capacity to identify antifungal resistance; and improved human, animal, and environmental surveillance to detect emerging resistance, monitor trends, and evaluate the effectiveness of efforts to decrease spread.

New taxonomic framework for Arthrodermataceae: a comprehensive analysis based on their phylogenetic reconstruction, divergence time estimation, phylogenetic split network, and phylogeography

The Arthrodermataceae, or dermatophytes, are a major family in the Onygenales and important from a public health safety perspective. Here, based on sequenced and downloaded from GenBank sequences, the evolutionary relationships of Arthrodermataceae were comprehensively studied via phylogenetic reconstruction, divergence time estimation, phylogenetic split network, and phylogeography analysis. These results showed the clades Ctenomyces, Epidermophyton, Guarromyces, Lophophyton, Microsporum, Paraphyton, and Trichophyton were all monophyletic groups, whereas Arthroderma and Nannizzia were polyphyletic. Among them, Arthroderma includes at least four different clades, Arthroderma I, III and IV are new clades in Arthrodermataceae. Nannizzia contains at least two different clades, Nannizzia I and Nannizzia II, but Nannizzia II was a new clade in Arthrodermataceae. The unclassified group, distributed in Japan and India, was incorrectly identified; it should be a new clade in Arthrodermataceae. The phylogenetic split network based on the ITS sequences provided strong support for the true relationships among the lineages in the reconstructed phylogenetic tree. A haplotype phylogenetic network based on the ITS sequences was used to visualize species evolution and geographic lineages relationships in all genera except Trichophyton. The new framework provided here for the phylogeny and taxonomy of Arthrodermataceae will facilitate the rapid identification of species in the family, which should useful for evaluating the results of preventive measures and interventions, as well as for conducting epidemiological studies.

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.

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.