Microsporum equinum

Microsporum equinum is a species of dermatophyte fungus responsible for causing dermatophytosis, commonly known as ringworm, in horses. This pathogen specifically targets keratinized tissues, such as the skin and hair follicles. While it is primarily a disease of horses, it can potentially affect other animals and humans, making it a significant zoonotic concern in stable management.

The infection manifests as circular or irregular patches of alopecia, where the coat appears broken and brittle. As the fungus invades the hair shafts, it disrupts the normal growth cycle, leading to thinning hair and the formation of crusts or scales on the skin surface. These lesions are typically found on the saddle area, face, neck, and limbs, where equipment friction may facilitate fungal entry.

Transmission occurs through direct contact with infected horses or indirect contact with contaminated surfaces. The fungus produces highly resilient spores that can survive in the environment for months, residing in stable walls, wooden fencing, grooming brushes, blankets, and tack. This durability makes environmental contamination the most challenging aspect of managing an outbreak.

Environmental factors play a crucial role in the development and spread of Microsporum equinum. Warm and humid conditions, combined with poor ventilation in horse barns, create an ideal climate for the proliferation of fungal spores. Stress, malnutrition, or pre-existing skin lesions can make individual horses more susceptible to the infection, as the fungus takes advantage of a compromised immune response.

Control measures are centered on breaking the cycle of transmission. Veterinarians typically prescribe topical antifungal therapies, and in severe cases, systemic medication. Essential preventive steps include:

• Strict quarantine for newly introduced animals.
• Daily cleaning and disinfection of grooming tools using appropriate fungicides.
• Minimizing the sharing of tack and blankets between different horses.
• Maintaining dry, well-ventilated housing to discourage fungal growth.