From the Guidelines
Ringworm is caused by a fungal infection, specifically by dermatophytes such as Trichophyton, Microsporum, and Epidermophyton species, which can be transmitted through direct skin-to-skin contact with an infected person or animal, or by touching contaminated items 1. The infection thrives in warm, moist environments, which is why it commonly affects areas like the groin, feet, and skin folds. Some key points to consider include:
- The characteristic ring-shaped rash develops as the fungus grows outward from the center of infection, creating a clearing in the middle while remaining active at the edges.
- People with weakened immune systems, those who live in hot, humid climates, or individuals who participate in contact sports are at higher risk for developing ringworm infections.
- According to a study published in 2011, skin contact with animals in public settings can also result in human infection, with 15 cases of ringworm infection caused by Trichophyton species and Microsporum gypseum documented among owners and family members who exhibited lambs in Georgia 1.
- Another study found that ringworm in 23 persons and multiple animal species was traced to a Microsporum canis infection in a hand-reared zoo tiger cub 1. Overall, it is essential to practice good hygiene and take precautions when interacting with animals or contaminated items to prevent the spread of ringworm infection.
From the Research
Causes of Ringworm
- Ringworm, also known as tinea infection, is a superficial fungal infection caused by three species of fungi: Epidermophyton, Microsporum, and Trichophyton 2.
- These fungi can spread by direct contact with other people, animals, and soil, as well as indirectly from fomites 2, 3.
- The dermatophytes have the ability to invade keratinized tissue, such as skin, hair, and nails, but are usually restricted to the nonliving cornified layer of the epidermis 4.
- The development of cell-mediated immunity correlated with delayed hypersensitivity and an inflammatory response is associated with clinical cure, whereas the lack of or a defective cell-mediated immunity predisposes the host to chronic or recurrent dermatophyte infection 4.
Types of Fungi that Cause Ringworm
- Trichophyton, Microsporum, and Epidermophyton are the common dermatophyte genera that cause superficial fungal infections in children and adults 3, 4.
- Trichophyton rubrum is the most common cause of chronic dermatophytosis, and it has been found to produce mannan, which suppresses or diminishes the inflammatory response 4.
- A new species of the T. mentagrophytes species complex, Trichophyton indotineae, has recently emerged and is notable for the severe infections it causes and its propensity for antifungal resistance 5.
Transmission and Risk Factors
- Dermatophyte infections can be acquired directly from contact with infected humans or animals or indirectly from exposure to contaminated soil or fomites 3, 4.
- The risk of developing ringworm is higher in people who have weakened immune systems, such as those with diabetes or HIV/AIDS 6.
- The use of certain medications, such as calcineurin inhibitors or corticosteroids, can also increase the risk of developing ringworm 6.