Home › Microbiology › Epidemiology and Ecology of Dermatophytes

Epidemiology and Ecology of Dermatophytes

Q: Which pathogens can cause tinea cruris?

Tinea cruris is caused by the anthropophilic fungus Epidermophyton floccosum. Anthropophilic dermatophytes (Epidermophyton floccosum) — predominantly affect the inguinal folds and shins, less commonly interdigital spaces and nails. In clinical material examined via microscopy, this pathogen reveals septate branching mycelium and rectangular arthrospores arranged in chains. By anatomical location, this condition is also classified as a dermatophytosis of the groin (tinea cruris).

Dermatophytosis

For medical students2 min readUpdated 2026-10-10

Dermatophytes are a group of microscopic fungi that cause superficial mycoses. Understanding their ecology and classification into three groups based on their natural reservoir is essential for taking a thorough epidemiological history.

EtiologyAbout 40 species of dermatophytes cause pathological processes in humans.

EcologyAll pathogens are divided into 3 groups: anthropophilic, zoophilic, and geophilic.

Risk FactorsVisiting high-humidity locations: bathhouses, swimming pools, communal showers.

General Principles of Epidemiology

The etiological structure of superficial mycoses is quite diverse: about 40 different species of dermatophytes are capable of causing pathological conditions in humans. Transmission of these fungi occurs through several main routes:

Direct contact: transmission of the pathogen occurs directly through physical contact with an infected person or animal.
Fomite transmission: infection is transmitted indirectly via contaminated everyday objects (combs, shared towels, footwear).
Environmental contact: infection occurs upon interaction with soil harboring spores of pathogenic fungi.

A major risk factor for developing mycoses is the regular visiting of public places with high humidity. These traditionally include bathhouses, shower rooms, and swimming pools, which provide ideal conditions for the survival and transmission of dermatophytes.

Anthropophilic Dermatophytes

Ecological classification divides dermatophytes into three groups depending on the natural reservoir of infection. The first group consists of anthropophilic dermatophytes. Their only reservoir is humans, and transmission occurs exclusively from human to human.

The main anthropophilic pathogens and the diseases they cause include:

Microsporum: caused by fungi such as Microsporum audouinii and Microsporum ferrugineum.
Trichophytosis: etiologic agents include Trichophyton tonsurans and Trichophyton violaceum.
Favus: the classical pathogen is Trichophyton schoenleinii.

Special attention should be given to fungi causing foot and nail infections (onychomycosis):

Trichophyton mentagrophytes var. interdigitale — a primary cause of tinea pedis.
Epidermophyton floccosum — causes tinea cruris as well as nail plate infections.
Trichophyton rubrum — the causative agent of tinea rubrum.

Zoophilic Dermatophytes

The second group is represented by zoophilic dermatophytes. The natural reservoir and source of infection in this case are various animals. Humans become infected through direct contact with an infected animal.

A specific and highly characteristic example of such interaction is Trichophyton verrucosum. This fungus is transmitted from cattle and causes a disease in humans known as "barn itch" or ringworm.

The main zoophilic reservoirs are distributed as follows:

Microsporum:
Microsporum canis — main reservoirs include cats, dogs, and horses.
Microsporum gallinae — affects poultry.
Microsporum nanum — pigs serve as the source of infection.
Trichophytosis:
Trichophyton verrucosum — cattle.
Trichophyton equinum — horses.
Trichophyton mentagrophytes (zoophilic variants) — circulates among rodents, mice, and hedgehogs.

Geophilic Dermatophytes

The third ecological group comprises geophilic dermatophytes. Their natural reservoir and permanent habitat is the soil. Human infection occurs through direct contact with contaminated earth.

A prominent example of geophilic infection is acquisition of the fungus Microsporum gypseum. Transmission of this pathogen frequently occurs during agricultural or gardening work with bare hands, leading to the colloquial term "gardener's microsporum."

Major geophilic fungi capable of causing microsporum infections in humans include species such as Microsporum cookei, Microsporum gypseum, and Microsporum fulvum.

Mnemonic

Ecological groups of dermatophytes are easy to remember by their specific examples: Anthropophiles — humans only (tinea pedis), Zoophiles — animals (T. verrucosum — cattle ringworm), Geophiles — soil (M. gypseum — gardener's ringworm).

Frequently asked questions

What laboratory diagnostic methods are used to detect and identify dermatophytes?

Microscopic, cultural, and several adjunctive methods are used to detect and identify dermatophytes.

Microscopic method — rapid diagnosis of clinical material (scrapings, hairs, nails) after treatment with a 10–15% KOH solution to visualize fungal elements.
Mycological method — inoculation on Sabouraud agar or wort agar for species identification based on colony growth characteristics.
Serological methods — detection of antibodies via complement fixation, hemagglutination inhibition, precipitation, or ELISA.
Allergy testing — intradermal skin tests with fungal allergens.
Biological assay — inoculation of laboratory animals (guinea pigs, mice).

Which pathogens can cause tinea cruris?

Tinea cruris is caused by the anthropophilic fungus Epidermophyton floccosum.

Anthropophilic dermatophytes (Epidermophyton floccosum) — predominantly affect the inguinal folds and shins, less commonly interdigital spaces and nails.

In clinical material examined via microscopy, this pathogen reveals septate branching mycelium and rectangular arthrospores arranged in chains. By anatomical location, this condition is also classified as a dermatophytosis of the groin (tinea cruris).

Which groups of antifungal agents are used for the targeted treatment of dermatophytoses?

Systemic and topical agents from several chemical classes are used for targeted treatment of dermatophytoses.

Azoles (imidazole and triazole derivatives) — clotrimazole, ketoconazole, econazole, miconazole, fluconazole, itraconazole.
Allylamines (N-methylnaphthalene derivatives) — terbinafine, naftifine.
Benzylamine derivatives — butenafine.
Morpholine derivatives — amorolfine.
Undecylenic acid derivatives — undecin, zincundan, mycoseptin.

Griseofulvin is also used in the treatment of superficial mycoses. The choice of drug formulation depends on the localization of the process, and topical therapy is combined with systemic drugs when necessary.

Why is it necessary for a physician to know the ecological classification of dermatophytes when suspecting a mycosis?

This is crucial for taking an accurate epidemiological history. Knowing whether a fungus is an anthropophile, zoophile, or geophile helps precisely identify the source of infection — an infected human, an animal, or contact with soil.

Which pathogens most frequently cause tinea pedis and nail infections?

The primary anthropophilic agents of these conditions are Trichophyton mentagrophytes var. interdigitale (tinea pedis), Epidermophyton floccosum (nail infections, tinea cruris), and Trichophyton rubrum (tinea rubrum).

What is the reservoir for the zoophilic fungus Microsporum canis?

The main source of infection and natural reservoir for Microsporum canis are cats, dogs, and horses.

How does "gardener's microsporum" transmission occur?

The disease is caused by the geophilic dermatophyte Microsporum gypseum. Infection occurs when handling contaminated soil with bare hands.

Go deeper

Clinical presentation of various types of microsporia
Pathophysiologic mechanisms and manifestations of tinea rubrum and favus
Specific laboratory diagnostics of dermatophytoses
Prevention of zoophilic mycoses in agriculture