Which infectious agent causes ringworm?

Which infectious agent causes ringworm?

• A. Bacteria
• B. Fungi
• C. Virus
• D. Protozoa

Answer: (B)

Ringworm is caused by fungi—dermatophytes that invade the dead, keratinized layers of skin, hair, and nails. The name ringworm comes from the typical ring-shaped rash rather than any worm involvement. The usual culprits are fungi such as Trichophyton, Microsporum, and Epidermophyton, which feed on keratin and spread through direct contact or contaminated objects and animals, especially in warm, moist environments. Diagnosis is supported by the characteristic appearance and lab tests like a potassium hydroxide prep or fungal culture. Treatment is with antifungal medications such as terbinafine or azoles, sometimes needing longer courses for nail infections. The other infectious agents—bacteria, viruses, and protozoa—cause different skin conditions and do not produce this dermatophyte ringworm pattern.

Ringworm is caused by fungi—dermatophytes that invade the dead, keratinized layers of skin, hair, and nails. The name ringworm comes from the typical ring-shaped rash rather than any worm involvement. The usual culprits are fungi such as Trichophyton, Microsporum, and Epidermophyton, which feed on keratin and spread through direct contact or contaminated objects and animals, especially in warm, moist environments. Diagnosis is supported by the characteristic appearance and lab tests like a potassium hydroxide prep or fungal culture. Treatment is with antifungal medications such as terbinafine or azoles, sometimes needing longer courses for nail infections. The other infectious agents—bacteria, viruses, and protozoa—cause different skin conditions and do not produce this dermatophyte ringworm pattern.