Non-dermatophyte Dermatoses Mimicking Dermatophytoses in Animals

Chrysosporium articulatum mimicking Trichophyton spp. infection in a cat: a case presentation and literature review

BACKGROUND

Dermatophytosis is a common skin infection of cats and many other animals. A reliable diagnosis is crucial because of the zoonotic potential of dermatophytes. The routine mycological diagnostic procedures for dermatophytosis are widely known, but in the case of some isolates, identification based on phenotypic characteristics may be incorrect. Infections caused by Chrysosporium spp. are usually described in reptiles, but in other animals they are uncommon.

CASE PRESENTATION

This study presents a description of a cat with dermatological lesions, that was mistakenly diagnosed with Trichophyton spp. dermatophytosis. Clinical material for mycological examination was collected from alopecic areas on the back of the neck, the ventral abdomen, and the hindlimbs. The initial identification based on phenotypic properties indicated Trichophyton spp. The result of the MALDI-ToF MS allowed the exclusion of the Trichophyton genus. Ultimately, the correct identification as Chrysosporium articulatum was obtained based on the sequencing of ribosomal genes.

CONCLUSIONS

Interpretation of the results of the mycological examination of samples collected from animals' skin or hair shafts is always challenging. Thus, careful consideration of the primary cause of the clinical lesions observed on the skin is mandatory, and the culture results are worth supporting by molecular methods.

Hyphae, pseudohyphae, yeasts, spherules, spores, and more: A review on the morphology and pathology of fungal and oomycete infections in the skin of domestic animals

Fungi are among the most common infectious agents affecting the skin of animals. The skin can serve as a port of entry for fungal infections, which can eventually become disseminated. In some regions of the world, oomycetes, such as Pythium and Lagenidium, are also responsible for a significant number of severe cutaneous infections. Histologic evaluation of fungal morphology, including size, shape, septation, branching, and budding characteristics, combined with the distribution of inflammatory infiltrates within different skin layers can potentially identify etiologic agents, guiding selection of antifungals and additional diagnostics. Fungal infections of the skin surface are typically caused by Malassezia and rarely Candida, with opportunistic fungi also capable of colonizing the skin surface, especially when the barrier is broken. Folliculocentric infections, caused by dermatophytes, result in mild to severe inflammation and can occasionally penetrate deep into the skin. A wide range of fungi, including agents of hyalohyphomycosis, phaeohyphomycosis, and dimorphic fungal infections, as well as oomycetes, result in nodular cutaneous and subcutaneous lesions. With the occasional exception of dimorphic fungi, fungal speciation often requires cultures performed on fresh tissues. However, molecular techniques such as pan-fungal polymerase chain reaction on paraffin blocks is becoming an increasingly useful tool to distinguish between cutaneous fungal pathogens. This review focuses on describing the clinical and histologic features of the most common fungal and oomycete infections affecting the skin of animals, divided according to distribution patterns of lesions and fungal or oomycete morphology.

First record of Trichophyton benhamiae isolated from domestic cats in Russia

We report a first case of Trichophyton benhamiae isolation from domestic cats in Russia. Genetically affiliated to European strains T. benhamiae were deposited in NCBI. T. benhamiae strains formed zonal cream-colored colonies, with reversum pigmentation ranging from intensive yellow to orange-brown in one and orange-brown to chocolate in the second strain. Mycelium is colorless, hyphae are septated, rapidly aging with the formation of arthrospores and microconidia. The formation of macroconidia was recorded after 48 hours. A favorable outcome of treatment was recorded after two weeks.

Bovine ringworm - Detection of Trichophyton verrucosum by SYBR-Green real-time PCR

Trichophyton verrucosum is the most commonly dermatophyte involved in cattle ringworm. This work reported a case of bovine dermatophytosis due to Trichophyton verrucosum detected from the clinical sample by SYBR-Green real-time PCR. The strategy was based on the DNA extraction directly from the infected hair followed by real-time PCR and melting-point analysis. A faster and differential diagnosis was observed when compared to the conventional mycological methodology for detection and identification of Trichophyton verrucosum.

Annular infectious dermatoses

Annular configuration is conspicuous in the clinical manifestation of many skin diseases and can be helpful for the diagnosis and differential diagnosis. Variations may include arciform, ring-form, annular, circinate, serpiginous, gyrated, polycyclic, targeted or figurate forms, in different colors, sizes, and numbers, with various textures and surfaces. In infectious dermatoses, the annular reactions can be specific or nonspecific, while the underlying mechanisms remain largely unknown. In the specific reactions caused by direct invasion of the pathogens, the contest between the centrifugal outspread of the infectious agents and the centripetal impedance of the host immune response is supposed to determine the final conformation. Examples include erythema infectiosum, orf, erythema multiforme, and pityriasis rosea of viral origin. Bacterial infections that may display annular lesions include erythrasma, erythema (chronicum) migrans of Lyme borreliosis, secondary syphilis, cutaneous tuberculosis, and leprosy. Superficial mycosis, such as dermatophytosis, candida intertrigo, tinea imbricata, and subcutaneous mycosis, such as chromoblastomycosis, and algae infection protothecosis, are characterized by annular progression of the skin lesions. The creeping serpiginous extension is an alarming sign for the diagnosis of cutaneous larva migrans. A better understanding of the virulence and pathogenicity of the pathogens and the way and type of immune response will help to clarify the pathogenesis.

Isolation of Dermatophytes from Infected Stray Dogs in Selangor, Malaysia

Background: Dermatophytosis is one of the most common skin diseases that affects cats and dogs. Geographic factors play an important role in determining prevalence, showing high rates of prevalence in warm and humid environments. Purpose: The aim of this study was to determine the macroscopic and microscopic identification of different types of dermatophytes present on stray dogs. Methods: The design of this study was laboratory-based research. Each sample was collected from an infection site (nail, hair, or skin) that was identified by conducting a physical examination of a stray dog that was infected with fungi. The skin scraping, nail clipping, and fur cutting samples were collected from infected dogs and then cultured on Sabouraud Dextrose Agar (SDA). The cultures were incubated at 26°C for five weeks. The isolates of fungi were then examined macroscopically and microscopically. The Lactophenol Cotton Blue (LPCB) staining technique was used for fungi morphology identification. Results: Overall, the most common type of dermatophytes that affected the dogs were Trichophyton spp. (64.70%), Aspergillus spp. (10.10%), Microsporum spp. (7.20%), and Curvularia spp. (5.60%). Conclusion: This study revealed the most common dermatophyte infections found on stray dogs in Selangor, Malaysia. This study can assist investigators in understanding the prevalence of the dermatophyte burden in stray dogs and help prevent further complication, such as the spread of illness, especially zoonotic infection.

Dermatophytosis in companion animals: A review

Dermatophytosis, a zoonotic disease, is caused by fungi of three main genera, namely, Micropsorum, Trichophyton, and Epidermophyton. Specific lesions of dermatophyte infections are localized in the face, legs, and/or tail. Skin lesions in infected animals demonstrate localized alopecia, erythema, and crust, which are more commonly known as ringworm. Factors that affect dermatophytosis include the dermatophyte species; virulence factors of the agent; and the immune status, age, and sex of the host. High levels of cortisol and pro-inflammatory cytokines have also been reported to play an important role in dermatophyte infection. This review aims to explore and understand factors that affect dermatophyte infection with an emphasis on the prevalence, clinical signs, pathogenesis, immune response, and the roles of cortisol and cytokines in companion animals infected by a dermatophyte.

PCR-terminal restriction fragment length polymorphism for direct detection and identification of dermatophytes in veterinary mycology

The biological diagnosis of dermatophytosis in veterinary medicine usually relies on direct microscopic examination and inoculation of the samples on appropriate culture media. However, identification of dermatophytes needs expertise, and cultures which require from days to weeks to be conclusive, may lack of sensitivity because of the quite common overgrowth of contaminants. Here we developed a polymerase chain reaction (PCR) assay based on terminal restriction fragment length polymorphism (TRFLP), which may improve sensitivity of the biological diagnosis and reduce the delay for initiation of treatment. This study was first conducted on pure cultures of various dermatophytes (27 species), yeasts (14 species) and moulds (45 species). After DNA extraction, the internal transcribed spacer (ITS)-28S region of ribosomal DNA was amplified with primers targeting specifically pathogenic dermatophytes, and species of interest were identified by TRFLP with appropriate restriction enzymes. After validation, this assay was applied to veterinary samples and results were compared to those obtained by direct microscopic examination and cultures. All target species were correctly identified, and none of the yeast or mould species was amplified, demonstrating specificity of the assay. Regarding clinical samples, the causative agent was detected by PCR-TRFLP from 97.1% of the samples with both positive direct microscopic examination and cultures. No dermatophytes were detected when both conventional tests were negative. PCR-TRFLP developed here demonstrated to be highly sensitive and specific, allowing rapid detection and direct identification of dermatophytes in veterinary practice. Therefore, this assay is especially suitable for the biological diagnosis of dermatophytosis in different animal species.

Epidemiological investigation and molecular typing of dermatophytosis caused by Microsporum canis in dogs and cats

The objective of the present study was investigate the prevalence of dermatophytes in dogs, cats and environment floor through molecular epidemiology tools to identify the genetic profile of these infectious agents. This was an observational study with cross-sectional surveys design. Sample were collected from the hair and skin of 52 dogs and cats with the clinical suspicion of dermatophytosis, over a period of one year in Maringá, in the state of Paraná, Brazil. Household samples (carpets and floor), were collected from animals that were positive for dermatophytosis by morphological colonies characteristics, and samples of dogs or cats living in the same household as with the positive animals were also collected. After mycological confirmation, molecular typing was performed by random amplified polymorphic DNA (RAPD). Microsporum canis was the unic dermatophyto isolated whose prevalence was 26.9% (14/52) in animals with the clinical suspicion of dermatophytosis and four other animals that lived with positive animals. As some animals had more than one lesion site, there were 22 total positive cultures from samples from animals and another ten from abiotic sources. The majority of the animals that provided positive cultures for M. canis were aged up to five months (77.8%) and were female (66.7%). Molecular typing using the P1 primer revealed genetically distinct profiles in the symptomatic, asymptomatic and environmental animal samples, or the same animal, furthermore, showed that M. canis could have microevolution.

New insights in dermatophyte research

Dermatophyte research has renewed interest because of changing human floras with changing socioeconomic conditions, and because of severe chronic infections in patients with congenital immune disorders. Main taxonomic traits at the generic level have changed considerably, and now fine-tuning at the species level with state-of-the-art technology has become urgent. Research on virulence factors focuses on secreted proteases now has support in genome data. It is speculated that most protease families are used for degrading hard keratin during nitrogen recycling in the environment, while others, such as Sub6 may have emerged as a result of ancestral gene duplication, and are likely to have specific roles during infection. Virulence may differ between mating partners of the same species and concepts of zoo- and anthropophily may require revision in some recently redefined species. Many of these questions benefit from international cooperation and exchange of materials. The aim of the ISHAM Working Group Dermatophytes aims to stimulate and coordinate international networking on these fungi.