Microsporum gypseum is a geophilic dermatophyte, a type of fungus. It primarily resides in soil, causing superficial infections of the skin, hair, and nails in mammals, including humans and animals. While found globally, its prevalence can vary by region, with some areas like South America reporting it more commonly than others, such as the United States or Europe. This fungus is known for its ability to break down keratin, the protein in skin, hair, and nails, allowing it to establish infections.
Sources and Transmission
The primary habitat of Microsporum gypseum is soil, especially soil rich in organic matter, where it degrades keratinized debris. Direct contact with contaminated soil is the main route of transmission to humans, especially for individuals involved in agricultural work, gardening, or other outdoor activities where exposure to soil is frequent. Children are also susceptible due to playing in dirt.
Transmission can also occur indirectly through animals. Animals such as dogs, cats, horses, and cattle can acquire the fungus from soil and act as carriers, even without showing symptoms. When humans interact with these animals, fungal spores can transfer, leading to infection. Direct person-to-person transmission is uncommon, unlike some other dermatophyte species.
Signs of Infection in Humans and Animals
Infections caused by Microsporum gypseum are known as dermatophytosis or ringworm, affecting the skin, hair, and sometimes nails. In humans, the most frequent manifestation on the body (tinea corporis) typically appears as a single or multiple round or oval, reddish, scaly patches or plaques. These lesions often have a raised, well-defined border and may show central clearing, giving them a ring-like appearance. Itching is a common symptom.
When the scalp is affected (tinea capitis), signs include patches of hair loss with scaling, inflammation, or pustules. Hair in the affected areas may become brittle and break off at the scalp surface. In animals, Microsporum gypseum infections also manifest as patches of hair loss (alopecia), with crusty or scaly skin and redness. These lesions can appear on various parts of the body, including the face, ears, and legs.
Diagnosis and Identification
Diagnosis of Microsporum gypseum infection begins with a visual examination of affected skin or hair by a medical professional. This assessment helps identify characteristic rash patterns consistent with dermatophytosis. A skin or hair scraping is then taken from the active border of the lesion for further investigation.
Samples are examined under a microscope using a potassium hydroxide (KOH) wet-mount preparation. The KOH solution dissolves skin cells and keratin, making fungal elements visible. While the KOH test confirms a fungal infection, a fungal culture is the definitive method to identify the specific species, like Microsporum gypseum. Unlike some other Microsporum species, infected hairs caused by M. gypseum generally do not fluoresce a bright greenish-yellow under a Wood’s lamp, though a dull yellow fluorescence has been occasionally noted.
Medical Treatment Approaches
Treatment for Microsporum gypseum infections depends on severity and location. For localized skin infections (tinea corporis), topical antifungal creams or lotions are the first line of treatment. These medications are applied directly to the affected area and contain agents such as azoles or allylamines. Topical therapy aims to eliminate the fungus on the skin surface.
More extensive infections, or those affecting the scalp (tinea capitis), require prescription oral antifungal medications. Topical creams may not adequately penetrate hair follicles where the fungus resides. Oral medications, such as griseofulvin or terbinafine, work systemically to reach the site of infection. Treatment duration varies, ranging from several weeks to a few months, depending on the medication and patient response.