Microsporia: Information & Microsporia Specialists

In most cases, microsporia is caused by the fungus Microsporum canis. This is a filamentous fungus that belongs to the dermatophyte group.

The pathogen is primarily found on the skin of animals. Transmission to humans occurs simply through contact with the animals. The main sources of infection are primarily dogs and cats, but also

• smaller (e.g., guinea pigs) and
• larger (e.g., horses) animals

as well as humans can transmit the parasite. Less commonly, infection can be caused by the pathogens

• Microsporum gypseum (via mold, geophilic microsporia) or
• Microsporum audouinii (from person to person, anthropophilic microsporia)

.

The pathogen: Microsporum canis

The pathogen Microsporum canis is what is known as a dermatophyte. As a parasitic fungus, it primarily causes the disease microsporia in cats and dogs. It therefore belongs to the group of zoophilic dermatophytes.

Since humans and other mammals can also become infected, the fungus is classified as a zoonotic pathogen.

On a suitable culture medium, the fungus forms colonies that are sharply defined and cotton-like in appearance. It is initially creamy white in color and later turns orange-yellowish.

When examined under a microscope, Microsporum canis exhibits septate hyphae. Along these hyphae are some smooth as well as club-shaped microconidia. The microconidia

• are approximately 10 to 25 × 35 to 11 µm in size,
• consist of about 6 to 18 chambers,
• have a thick, rough wall, and nodular ends.

Incubation Period and Epidemiology of Microsporia

Microsporia is highly contagious. The period between infection and the onset of symptoms (incubation period) ranges from a few days to several weeks.

Microsporia is a disease found worldwide. The fungus Microsporum canis is most commonly transmitted from animals to humans.

The group at highest risk for developing microsporia is children who play with infected animals. The disease is relatively rare after puberty.

Consequently, the pathogens can spread in

• daycare centers and preschools,
• schools, or
• children’s homes

.

Infection is facilitated by

• a warm, humid climate,
• existing circulatory disorders,
• heavy sweating,
• diseases such as diabetes mellitus,
• a weakened immune system,
• the use of antibiotics or corticosteroid medications.

The scalp is particularly affected by microsporia in children. This is why it is referred to as a fungal infection of the scalp (tinea capitis).

The most distinctive symptoms of microsporia are round, reddened areas of inflammation. They are covered with fine scales and look as if they have been dusted with flour. In cases of microsporia, the hair breaks off just above the skin’s surface in the affected areas.

In many cases, microsporia also affects the skin

• on the face,
• on the extremities
• as well as on the trunk

. There, microsporia manifests as small, light-red nodules. These develop into itchy, round patches with a clearly defined border. Microsporia on these areas of the skin, like on the scalp, may be accompanied by scaling.

The edges of the lesions are often dotted with pustules. In addition, microsporia can cause severe inflammation in the affected areas.

Skin fungus on the scalp © ZayNyi | AdobeStock

As soon as symptoms suggestive of microsporia are observed, it is essential to consult a dermatologist. Treatment of the condition also serves to prevent further spread.

In general, all species of Microsporum fluoresce greenish-yellow under Wood’s light (a special lamp). Microsporia can therefore be diagnosed during an initial rapid examination.

A positive test result is highly indicative of microsporia. However, a negative result does not necessarily mean that microsporia is absent.

The diagnosis must therefore still be confirmed microscopically. To do this, a fungal culture is prepared after taking a smear. This is the only way to definitively confirm microsporia.

Sometimes the affected areas in microsporia are extremely inflamed. In such cases, the body’s immune system typically responds quickly to fight the infection. As a result, microsporia can often heal on its own.

However, healing without medication can be a lengthy process. Microsporia can be treated more quickly with antifungal medications. These medications can also relieve often bothersome symptoms such as itching and prevent the spread of microsporia.

Depending on the severity of microsporia, topical application of local antifungal medications may be sufficient. These are simply applied to the affected areas of the skin.

Systemic medication is required if

• the patient has a more severe infection and
• the scalp is also affected.

Systemic therapy refers to the treatment of the entire body. Instead of ointments or similar products, the patient receives tablets or an infusion. The active ingredients combat the pathogen throughout the body and also reach the hair follicles.

The active ingredients most commonly used to treat microsporia are

• terbinafine,
• fluconazole,
• griseofulvin, or
• itraconazole

are used.

However, doctors also recommend local treatment for microsporia to speed up recovery. Cutting the hair short can also help speed up the healing process somewhat, especially when the scalp is affected.

Microsporia is generally not a serious condition. However, it is often quite persistent.

It usually places a significant burden on the affected patient due to itching and possible hair loss.

Hair that has fallen out will grow back completely after treatment for microsporia. 

Children, in particular, are at risk of contracting microsporia from stray cats while on vacation in southern countries. Contact with these animals should therefore be avoided whenever possible. Microsporia often shows no symptoms in animals, meaning that even healthy animals can transmit the pathogen.

However, people should also exercise caution on their own farms. Here, too, dogs and cats are particularly prone to microsporia.

Although a vaccine against microsporia is available, primarily for pets, its effectiveness lasts for a maximum of one year and must be regularly renewed. Even with vaccinated animals, infection with microsporia cannot be completely ruled out.