dermatophytes

Dermatophytes are fungi that cause skin, hair, and nail infections due to their ability to utilize keratin. Infections caused by these fungi are also sometimes known as "ringworm" or "tinea." Despite the name "ringworm," this infection is not caused by a worm, but by a type of fungus called a dermatophyte. Dermatophytes can live on moist areas of the skin, on environmental surfaces, and on household items such as clothing, towels, and bedding.
Anyone can get a dermatophyte infection, including animals.
The organisms are transmitted by either direct contact with infected host (human or animal) or by direct or indirect contact with infected exfoliated skin or hair in combs, hair brushes, clothing, furniture, theatre seats, caps, bed linens, towels, hotel rugs, and locker room floors.

Depending on the species the organism may be viable in the environment for up to 15 months. There is an increased susceptibility to infection when there is a preexisting injury to the skin such as scares, burns, marching, excessive temperature and humidity.There are many different species of dermatophytes that can cause infection in humans. Two of the most common types are Trichophyton rubrum and Trichophyton tonsurans, which are usually transmitted from person to person. Another common dermatophyte is Microsporum canis, which is transmitted to people from animals such as cats and dogs. Dermatophytes like to live on moist areas of the skin, such as places where there are skin folds. They can also live on household items, such as clothing, towels, and bedding.

Dermatophytes are classified as anthropophilic, zoophilic or geophilic according to their normal habitat.

Anthropophilic dermatophytes are restricted to human hosts and produce a mild, chronic inflammation.

Zoophilic organisms are found primarily in animals and cause marked inflammatory reactions in humans who have contact with infected cats, dogs, cattle, horses, birds, or other animals. This is followed by a rapid termination of the infection.

Geophilic species are usually recovered from the soil but occasionally infect humans and animals. They cause a marked inflammatory reaction, which limits the spread of the infection and may lead to a spontaneous cure but may also leave scars

The dermatophytes consist of three genera:

Epidermophyton produces only macroconidia, no microconidia and consists of 2 species, one of which is a pathogen.
Microsporum - Both microconidia and rough-walled macroconidia characterize Microsporum species. There are 19 described species but only 9 are involved in human or animal infections.
Trichophyton - When produced the macroconidia of Trichophyton species are smooth-walled. There are 22 species, most causing infections in humans or animals.

At the National Centre for Mycology -

about 58% of the dermatophyte species isolated are Trichophyton rubrum
27% are T. mentagrophytes
7% are T. verrucosum
3% are T. tonsurans


Causes of dermatophyte infections

Dermatophyte infections are usually spread through direct contact with an infected person or animal. Clothing, bedding and towels can also become contaminated and spread the infection. Symptoms typically appear between 4 and 14 days following exposure.



Symptoms of dermatophyte infections

Dermatophyte infections can affect the skin on almost any area of the body, such as the scalp, legs, arms, feet groin, and nails. These infections are usually itchy. Redness, scaling, cracking of the skin, or a ring-shaped rash may occur. If the infection involves the scalp or beard, hair may fall out. Infected nails become discolored, thick, and may possibly crumble. More serious infections may lead to an abscess or cellulitis.



Diagnosis of dermatophyte infections

Your doctor may diagnose you based on your symptoms and a physical examination. To confirm the diagnosis, your doctor may take scrapings of affected skin or clippings of affected nails. These can be examined under a microscope and may be sent to a laboratory for a fungal culture.


reatment for dermatophyte infections

The particular medication and duration of treatment depends on the location of the infection. Scalp infections usually require treatment with an oral antifungal medication. Infections of other areas of the skin can be treated with topical antifungal medications. Nail infections can be challenging to treat, and may be treated with oral and/or topical antifungal medications. Courses of treatment may range from 2 to 6 weeks or more, depending on the severity of the infection and your doctor's recommendations.


Risk & Prevention

Who gets dermatophyte infections?

Dermatophyte infections are very common. They can affect anyone, including people who are healthy. Dermatophyte infections may be more common among people with suppressed immune systems, people who use communal baths, and people who are involved in contact sports such as wrestling, and people who have close contact with animals. Some species are found more commonly in hot, humid environments. Outbreaks of infections can occur in schools, households, and institutional settings.
How can I prevent a dermatophyte infection?

Good hygiene, such as regular handwashing, is important. People should avoid sharing hairbrushes, hats, and other articles of clothing that may come into contact with infected areas. Pets with signs of skin disease should be seen by a veterinarian. Beauty salons and barbershops should disinfect instruments with approved disinfectants after each use. Contact your local and/or state health department for specific guidelines and regulations in your area.
There is a ringworm outbreak in my child's school/daycare center. What should I do?

You should contact your local health department. Your local health department may have information about how long children with ringworm should remain out of school/daycare. Tell your child not to share personal items, such as clothing, hairbrushes and hats, with other people. Encourage frequent handwashing. Take your child to a pediatrician if he or she develops symptoms.
My pet has ringworm and I am worried about ringworm in my house. What should I do?

Make sure your pet has been seen by a veterinarian. If you develop symptoms, you should see your doctor. There are no federal guidelines about ringworm and environmental disinfection. Infection may occur through direct contact with an infected person or animal or from contact with contaminated environmental surfaces. Regular cleaning may help remove fungal spores from the home environment. Make sure to use cleaning products according to the manufacturer's labeling, and never mix cleaning products, as harmful fumes may result. For surfaces that are safe to bleach, a quarter-cup of bleach in a gallon of water can be used for disinfection. For fabrics or soft items that are washable, washing with hot water and drying with hot air may help to kill the fungus.