RINGWORM is a common fungal skin infection of horses. The fungus lives on the outer layers of the skin as it has a predilection for keratin, the protein found in hair. While ringworm rarely poses a major health risk to the horse, it is highly contagious and preventing its spread can be challenging. It is also classed as a zoonotic condition, meaning that people can potentially be infected.
Ringworm is most common in young horses and typically first shows up as patches of raised or bumpy hair 1-4 weeks after infection. Hair loss follows to give the classic ringworm appearance of 1-2cm circular patches of grey, flaky skin with rough or broken hairs around the edges (figure 1). These can appear anywhere on the body but are most common on the head, saddle region and girth. The horse may be mildly itchy when the lesions first develop but generally ringworm does not cause any major problems unless the lesions are under the saddle or girth, where they may become sore and inflamed if the horse is worked under tack.
Most bouts of ringworm are mild and the horse will recover within 1-3 months. The major problem is that during this time thousands of ringworm spores will be shed into the horse’s environment. These spores can remain infectious for up to a year, especially on porous surfaces such as untreated timber. For this reason, treatment of the condition and efforts to contain its spread are recommended. Horses with ringworm may be precluded from travel, competition and sales, resulting in a significant economic impact for owners.
If you notice any suspicious lesions on a horse’s coat it is best to immediately isolate that individual from others by confining it in a stable or paddock where it cannot have any direct contact with other horses. Seek veterinary attention as a skin scrape or hair sample may be needed to confirm the diagnosis. A vet can also prescribe antifungal skin washes which are usually very effective.
If the horse has a heavy winter coat consider clipping it before starting treatment to reduce the number of spores being shed. The clippings will be infectious and so should be swept up and placed in an enclosed plastic bin for disposal, or burnt. The clipper blades will also need to be disinfected.
Gloves should be worn while handling and treating the horse – I find rubber washing gloves to be better than disposable gloves, as they are more durable and also cover the wrists. Overalls, waterproof boots, eye protection and a hat are also recommended to reduce the chances of spores contacting your own skin or hair.
Designated protective clothing should be kept in the isolation area – avoid wearing them elsewhere on the premises as you’ll just end up spreading infectious spores around. Be careful to avoid skin contact with the outer surfaces when removing protective clothing, and wash your hands with soap and water once finished handling the animal.
Antifungal skin washes should be diluted as per the label recommendations for optimal effectiveness and used as prescribed by the vet. First, soak any crusts on the affected areas with the diluted wash and gently lift them off with a stiff-bristled brush.
Then spray or wipe the entire hair coat to treat any developing lesions. The skin lesions and the surrounding areas should then be treated again every three days for a total of 3-4 treatments.
Keep all tack, buckets, rugs, brushes etc. used on ringworm cases separate from those for all other horses. Coloured insulation tape can be used to identify equipment that should remain in the isolation area.
Ideally ringworm cases should be handled by separate personnel, but where this is not feasible these animals should be treated and handled last. Keep stable fittings to a minimum and avoid placing the horse in a stall with untreated timber finishes or porous surfaces, such as unsealed blockwork.
The horse should remain in isolation and avoid moving other horses off the premises until the infection is cleared. Inspect all in-contact horses daily for any signs of ringworm infection and isolate them immediately if you have any concerns.
Once the horse has recovered the stable should be completely mucked out and infected bedding composted away from contact with other horses. Scrub all surfaces and equipment with water and a detergent to remove dirt before applying a correctly diluted disinfectant that is active against fungal spores – check the label before you use it. A 1:40 dilution of bleach (25 ml per litre of water) is a cost-effective and readily available option and can also be used to wipe down tack, gates, mangers and any other surfaces the horse may have contacted. Bleach solutions may cause discolouration of rugs and fabrics so test them first on a small area.
A 60 degree washing machine cycle will also kill ringworm spores and can be used to wash girth sleeves, saddle cloths and protective clothing etc. Leave stables empty and exposed to sunlight if possible after cleaning, as ultraviolet light also helps kill fungal spores.
While efforts to contain an outbreak of ringworm are time-consuming in the short term, they can greatly reduce the risk of future infections on the premises if implemented effectively. Most animals will make a rapid and full recovery and hopefully their owner can get back to travel and competition without suffering any long lasting disruption.