Bit & Bridle

Equine Ringworm (Dermatophytosis)

Other Names

Dermatophytosis, girth itch, saddle rash, barn itch, dermatomycosis. In horses, ringworm is most commonly caused by Trichophyton equinum or Microsporum equinum.

What is Equine Ringworm?

Despite its name, ringworm is not a worm at all — it is a fungal skin infection caused by dermatophytes, a group of fungi that invade and feed on keratin, the structural protein found in skin, hair, and hooves. In horses, ringworm is one of the most common contagious skin diseases encountered in the UK, particularly in stabled horses during autumn and winter when immunity can be lower and warm, humid stable conditions favour fungal growth.

Equine ringworm is caused primarily by two species: Trichophyton equinum (the most common equine-specific species) and Microsporum equinum, though T. verrucosum (a cattle dermatophyte) and M. canis (from cats and dogs) can occasionally infect horses. The infection name “ringworm” derives from the roughly circular, ring-like lesions it can produce, though in horses the lesions are not always ring-shaped.

Ringworm is zoonotic — it can be transmitted from horses to humans. Horse owners, grooms, and riders who handle infected horses are at real risk of developing skin lesions themselves. Prompt treatment and good hygiene are important for public health reasons as well as animal welfare.

The disease is highly contagious between horses and spreads readily through shared equipment. A single infected horse in a yard can quickly expose the entire population if biosecurity measures are not taken promptly.

What Causes Equine Ringworm?

Dermatophyte fungi invade the outer layers of skin and hair follicles, digesting keratin as a food source. They do not invade living tissue or enter the bloodstream. Infection occurs when fungal spores contact the skin — spores can survive for months to years in the environment, particularly in dry conditions such as wooden stable fixtures, leather tack, and grooming equipment.

Transmission routes include:

  • Direct contact: Horse-to-horse contact, particularly at shows, competitions, shared stabling, or through fields where infected horses have grazed
  • Indirect contact: Shared grooming brushes, body brushes, dandy brushes, rugs, numnahs, saddle pads, girths, and bridle components are the most common vectors in equine practice
  • Contaminated environment: Stable walls, fencing, wooden posts, and trailers can harbour viable spores
  • Human hands and clothing: Handlers moving between infected and uninfected horses without changing gloves or washing hands

Young horses (under 5 years) and immunosuppressed horses are most susceptible. Animals with good immunity often resist infection or clear it spontaneously. Stress, nutritional deficiencies (particularly vitamin A), and illness can lower resistance. Overcrowding, poor ventilation, and lack of sunlight (UV light has natural antifungal properties) all favour the spread of ringworm in stable yards.

Symptoms and Signs

Signs typically appear 1–4 weeks after exposure. The early stages can be subtle and easily missed, but lesions typically progress as follows:

  • Early lesions: Small, raised, round areas where the hair stands on end (erect hair), often with a grey or ashy appearance to the skin surface
  • Hair loss (alopecia): Patches of hair loss develop, often beginning in areas where tack sits — the girth area, saddle region, neck, and face are particularly common sites
  • Scabbing and crusting: Circular or irregular lesions with scabs that may be slightly raised; removal of the scab may reveal a raw, moist surface beneath
  • Variable itchiness: Some horses show significant pruritus; others show none. Pruritus is less consistent than in sweet itch or mange
  • Multiple lesions: Lesions may coalesce (merge) as infection spreads
  • Tack-related distribution: Girth and saddle areas are highly characteristic sites given friction and moisture; infection can also spread to any skin surface

Lesions can appear virtually anywhere on the body but are particularly common at points of tack contact (girth, saddle, bridle), the face, and the neck. In young foals, generalised infection across large body areas can occur.

Diagnosis

Diagnosis is based on clinical appearance, history of contagion within a yard, and laboratory confirmation. Your vet may perform the following:

Wood’s lamp examination: Some dermatophytes fluoresce under ultraviolet light (M. canis fluoresces apple-green). However, T. equinum and T. verrucosum do not fluoresce, so a negative Wood’s lamp result does not rule out ringworm in horses.

Hair and scale samples: Samples taken from the active edge of a lesion (not the centre) and submitted for fungal culture. Results take 1–3 weeks. Direct microscopy may provide faster, though less sensitive, results.

Skin biopsy: In cases where diagnosis is uncertain, histopathology can confirm dermatophyte invasion of the hair follicle.

It is worth noting that ringworm lesions can superficially resemble sweet itch lesions, rain scald (Dermatophilus congolensis), and other skin conditions. Accurate diagnosis is important before treatment to avoid inappropriate management.

Treatment

In healthy adult horses with intact immunity, ringworm often resolves spontaneously within 6–12 weeks. However, treatment shortens the infectious period, reduces spread to other horses and humans, and speeds clinical resolution.

Topical antifungal treatments: The mainstay of treatment. Products containing enilconazole (available as a wash for horses) are highly effective and widely used. Natamycin, miconazole, and clotrimazole preparations are also used. The lesions and surrounding skin should be treated 2–3 times weekly for a minimum of 3–4 weeks.

Whole-body washes: In horses with widespread lesions or where multiple horses on a yard are affected, whole-body antifungal washes are practical and help treat subclinical lesions not yet visible. Enilconazole solution diluted as per instructions is effective.

Systemic antifungals: Oral griseofulvin was historically used but is no longer available in the UK. Other systemic antifungals are rarely needed in otherwise healthy horses but may be considered in severe or non-responsive cases under veterinary guidance.

Crusts and scales: Softening and gently removing crusts before applying antifungal preparations improves penetration and efficacy. Use gloves when handling infected skin — this protects you and reduces environmental contamination.

Equipment and environment: Treating the horse without simultaneously decontaminating tack and equipment is futile — reinfection will occur. All grooming equipment, rugs, numnahs, girths, and saddle pads used on infected horses must be either disinfected or discarded. Enilconazole or 1% bleach solution is effective on equipment; leather may need specialist treatment.

Prevention

  • Never share grooming equipment, rugs, or tack between horses — assign individual sets to each animal
  • Quarantine and carefully examine new arrivals to the yard before allowing contact with resident horses
  • Maintain good ventilation in stables — ringworm thrives in warm, humid, poorly ventilated conditions
  • Ensure horses receive adequate nutrition — vitamin A deficiency increases susceptibility
  • Disinfect stable walls, wooden fixtures, and trailer interiors regularly, especially after housing an infected horse
  • Wear gloves when handling any horse with suspicious skin lesions and wash hands thoroughly afterwards
  • Do not use infected horses at shows or competitions until fully clear of disease

A vaccine against equine ringworm (T. equinum) is available in some European countries and has been used with success in certain contexts. Discuss availability and suitability with your vet.

When to Call the Vet

  • Multiple horses on the yard develop similar skin lesions simultaneously
  • Lesions are spreading rapidly or affecting a large proportion of the horse’s body surface
  • A horse is not responding to topical antifungal treatment after 4–6 weeks
  • You or anyone on the yard develops skin lesions after contact with an affected horse — seek advice from your GP as well as your vet
  • The diagnosis is uncertain and other conditions (rain scald, sweet itch, mange) need to be excluded
  • Foals or young horses develop generalised, severe lesions

Prognosis

The prognosis for equine ringworm is excellent. The vast majority of affected horses recover fully — either spontaneously or with appropriate treatment — within 6–12 weeks. Scarring is uncommon unless secondary bacterial infection occurs or lesions are subjected to ongoing trauma. Horses that have had ringworm develop partial immunity and are less susceptible to reinfection with the same species, though not necessarily to other dermatophyte species.

The main risks are zoonotic transmission to humans and spread to other horses on the yard. Both are manageable with prompt identification, treatment, and good biosecurity.

Frequently Asked Questions

Can I catch ringworm from my horse?

Yes. Ringworm is zoonotic — the fungi responsible for equine ringworm can infect humans, causing red, itchy, ring-shaped skin lesions. Children, elderly people, and immunocompromised individuals are at higher risk. Always wear gloves when handling an infected horse, wash hands thoroughly afterwards, and change clothes before contact with family members. If you develop skin lesions, consult your GP.

How long is a horse with ringworm infectious?

A horse is infectious from when lesions first appear until the infection is fully resolved and new hair has regrown. This can be 6–12 weeks in untreated horses. With appropriate antifungal treatment, the infectious period is significantly shortened. Do not return an affected horse to shared facilities or competitions until lesions have fully resolved.

My whole yard has ringworm — what should I do?

This is unfortunately common, given ringworm’s highly contagious nature. The approach requires treating all affected horses simultaneously with antifungal washes, disinfecting all shared equipment and stable fixtures, assigning individual grooming kits to each horse, and maintaining strict hygiene between horses. Contact your vet for guidance on a yard-wide treatment protocol. Enilconazole whole-body washes applied 2–3 times weekly across all horses is the standard approach.

Can ringworm spread through a fence or field?

Spores can survive on wooden fencing, posts, and field shelters for extended periods — potentially months. Horses rubbing on shared fence posts can transfer infection. If you have an infected horse, check that it is not sharing fence lines with other horses and disinfect any wooden surfaces it has rubbed against. Spores are less viable in wet outdoor conditions and under UV light, so risk is generally lower in open fields than in stable environments.