Trichophyton tonsurans - Pathogenesis, Host Immunity, Risk factors, Epidemiology, Reservoir, Transmission

Pathogenesis of Trichophyton tonsurans

Trichophyton tonsurans infection is typically restricted to upper layers of the epidermis but in some cases, deeper infections may occur. Trichophyton tonsurans grows down into the stratum corneum where it is able to invade keratin. It invades hair and sporulates in the hair shaft. As a result, the infected hair bursts and curls with hair breaking off, resulting in black dots on the scalp.

Dermatophytes such as Trichophyton tonsurans, grow within dead, keratinized tissue and epidermis of its human host. Trichophyton tonsurans are able to produce keratinolytic protease enzyme (keratinase) in vivo which aids the fungi to penetrate into living cells and use keratin as a source of nutrition. This results in arthrospore formation entirely within the hair shaft (endothrix) and breaking off of hair.

In humans, males are more often infected than females.

Host Immunity against Trichophyton tonsurans

Trichophyton tonsurans infection does not elicit strong inflammatory responses. The fungi are able to suppress cellular immune responses including lymphocytes (particularly T cells).

A pathologically important fungal cell wall component is mannan, which also suppresses host immune responses. However, the exact mechanism remains undiscovered.

The fungi have been associated with the induction of an id reaction in which acute dermatitis develops for days or weeks at skin locations that are distant from the infectious site or initial inflammatory area.

Risk factors of Trichophyton tonsurans

Risk factors of Trichophyton tonsurans include diabetes, humid environment, high blood pressure, weak immune system, excessive sweating, cracks in feet, and recurrent hand trauma.

The profession and gender of an individual also determine fungal infection. Farmworkers, machine operators, mechanics, people who work with chemicals, electricity workers, gas workers, and pet owners have a higher incidence of infection while on the basis of gender, more males are infected than females.

Epidemiology of Trichophyton tonsurans

Trichophyton tonsurans are worldwide in distribution. However, it is endemic in Latin America, Mexico, and Africa. It can be both Anthropophilic or Zoophilic.

Reservoir, Source of Trichophyton tonsurans

Humans and animals are natural reservoirs for Trichophyton tonsurans, which can be Anthropophilic or Zoophilic. An infected individual is the source of Anthropophilic Trichophyton tonsurans.

Transmission of Trichophyton tonsurans

Infected companion animals transmit Trichophyton tonsurans to humans due to close proximity living.

Trichophyton tonsurans can be transmitted via contact with infected skin or hair. Fomites such as combs, towels, brushes, barber shop clippers, or scissors are responsible for the transmission of Trichophyton tonsurans from one person to another.

Use of unhygienic common showers, dressing rooms, and swimming pools where desquamated skin is a source of Trichophyton tonsurans infection is responsible for the transmission of athlete’s foot.

Children are more susceptible to Trichophyton tonsurans infection.