Ringworm is a common skin infection caused by a type of fungus called dermatophytes, which thrive on the dead keratin in skin, hair, and nails. The characteristic circular rash led to the term “ringworm,” though it has no connection to actual worms or parasites. Humans can contract this infection from cattle because it is a zoonotic disease, meaning it can be transmitted between animals and people.
The Specific Fungus and Its Prevalence in Cattle
The fungus Trichophyton verrucosum is the primary cause of ringworm in cattle and the strain most often transmitted to humans. This dermatophyte accounts for over 90% of bovine cases found in infected herds. The infection is common in cattle populations, with prevalence rates sometimes observed between 10% and 20% in farm settings.
Ringworm is particularly widespread among young animals, such as calves, which often lack the developed immunity of adult cattle. The fungal infection typically appears as circular, greyish-white patches that are crusty and raised. These lesions are most frequently observed on the head, neck, and around the eyes, resulting in hair loss.
How Ringworm Spreads from Cow to Human
Transmission of fungal spores from cattle to humans is highly efficient and occurs through two main pathways. The most direct route is physical contact with an infected animal, such as handling a cow with active ringworm lesions. People who work closely with cattle, especially those in farming or veterinary care, have an increased risk from this direct exposure.
The second significant route is indirect transmission through contaminated objects, known as fomites. Fungal spores can be transferred to items like fencing, grooming tools, halters, feed carts, and barn surfaces. The spores of Trichophyton verrucosum are notably resilient and can survive in the environment for many months, sometimes up to a year or more.
This long survival time means a person does not need to touch the animal itself to become infected. Simply handling contaminated equipment or touching surfaces where an infected animal has been rubbing can facilitate the spread. The risk is also heightened when cattle are housed in close quarters, which increases the concentration of spores.
Recognizing and Treating Human Ringworm
When ringworm is contracted from cattle, it most commonly presents as tinea corporis, a fungal infection of the body’s skin. The classic sign is an itchy, reddish rash that forms a circular or ring-shaped pattern. This rash has a slightly raised, scaly border and a clearer center. In adults, lesions are frequently found on the upper limbs and hands due to handling animals.
Diagnosis is often made by a healthcare provider based on the rash’s distinct appearance, though confirmation may involve a skin scraping examined under a microscope. Mild cases are typically treated with over-the-counter topical antifungal creams containing ingredients like clotrimazole or terbinafine. These creams are applied directly to the affected area and usually clear the infection within a few weeks.
More severe or persistent infections may necessitate a prescription for stronger topical agents or oral antifungal medications. Individuals who work with cattle can take specific steps to minimize their risk of exposure, including wearing protective gloves when handling animals, maintaining strict hand hygiene after contact, and regularly cleaning and disinfecting shared farm equipment.