A horse’s skin is surprisingly delicate and does not tolerate repeated soakings.
Relentlessly damp skin is vulnerable to infections such as ringworm, rain scald and mud fever. While none of these are life-threatening, ringworm can be challenging to bring under control — especially when waterlogged fields make providing clean, dry turn-out all but impossible.
Ringworm has many different disguises, which makes diagnosis difficult.
Even the name is misleading as it is not usually ring-shaped and nor has it anything to do with worms.
What is certain is that this fungal skin infection spreads rapidly among both horses and occasionally humans. While the condition tends to affect young or more debilitated horses, ringworm should be considered a possibility in almost any equine scabby skin condition. Anything suspicious can be isolated, treated or both, to reduce spread.
Ringworm (pictured right) is spread by fungal spores that land on the horse’s coat. If the protective outer layers of the skin are damaged, perhaps because of damp, fly bites or rubbing tack, the spores can invade and grow with the hair for several weeks.
Signs will begin to emerge, typically crusty grey lesions with accompanying hair loss. Ringworm can also appear as hair loss with less scaling of the skin, or as small, crusty spots or widespread scurfy dandruff.
Early lesions may show themselves as rough patches of hair that stand up at an odd angle, before tufts of infected hair begin to fall out. Unless infected with bacteria, the lesions are not normally itchy.
One clue is lesion location. They commonly appear where tack rubs, such as in the girth area, or around the face, neck or flanks. More than one case of skin disease at the yard points to something infectious and should deepen suspicion, as ringworm is the most likely culprit.
There is also the fact that the condition is self-limiting, meaning that it will resolve itself — usually within a few weeks to months. An individual horse with persistent lesions is unlikely to have ringworm.
Most probably he has sarcoids, a chronic bacterial infection or, more rarely, an auto-immune skin disease.
Diagnosis can be confirmed by microscopy on hair samples. The gold standard diagnostic test is a fungal culture, but obtaining results can take a fortnight or more since fungi are slow growing. In the meantime, the nasty skin blemishes can spread right around a yard.
Ringworm treatment
Some yards manage ringworm by benign neglect, doing nothing and hoping the problem will gradually disappear. This is not ideal because the environment will be contaminated with fungal spores, however, which may linger for 12 months or more.
Clean, dry turn-out is almost impossible at this time of year
Various treatments are available. Rinses are the best choice — the specific licensed prescription product Imaverol (properly called enilconazole) is easily sponged over large areas of the coat and has long-lasting effects. Lime sulphur is another effective — albeit smelly — rinse option.
Special shampoos are active for a shorter time and the process of shampooing and rinsing can damage the fragile, infected hair. Antifungal creams tend to be less effective, since the spores can be found more than 6cm from the lesions and may also be present where there are no visible signs.
In the past, treatment was available as a powder to go in the feed or for administration by stomach tube. There is no scientific proof that these powders work in horses, however, and the fact that they are not safe to be handled by pregnant women means that they are best avoided.
Affected areas will not look right until the hair grows back and may sometimes develop odd dappled markings. Whatever the treatment, minimise spread by not sharing any kit. Avoid clipping a ringworm-infected horse as the infected hairs will go everywhere and contaminate the clippers.
Major efforts are required to fully eliminate the infection from the environment — ask your vet for more advice.
Managing in the mud
Rain scald and mud fever are annoyingly common in wet, muddy conditions.
These skin conditions are similar in nature and can be hugely problematic.
Rain scald affects the back and hindquarters, while mud fever affects the lower limbs. The term mud fever actually refers to a range of skin reactions to different irritants, correctly termed pastern dermatitis.
Mud fever
In the same way as there are a multitude of treatments for the common cold, there are a variety of mud fever remedies. No single cure is effective for all cases and careful consideration must be given to other underlying causes. Removing the horse from the wet and mud will improve matters, although this is often easier said than done.
If your horse must be turned out, do not rely on barrier creams as protection against mud fever or rain scald. Creams should be used with caution as they may provide a suitable anaerobic environment for the bacteria to grow between the waterlogged skin and the greasy layers applied as protection.
It will help if you can allow an affected horse some time to stand in a dry stable each day. If his legs are wet and muddy when you bring him in, allow them to dry thoroughly before using a soft brush to remove the mud.
Dry shavings or a deep straw bed are ideal for absorbing wetness from waterlogged limbs, as are moisture-wicking leg wraps.
Rain scald
Further skin irritations include sand schools, scrubbing the legs with stiff brushes and excessive washing to remove mud. All of these can create tiny scratches that allow bacteria to invade.
It is more likely that your horse’s pastern dermatitis involves bacteria if the skin seems red and sore, as in the human condition impetigo. When a scab is loosened the hair will come away with it and reveal a raw area with underlying pus.
Views vary, but the general consensus is that infected scabs should be carefully removed and the legs cleaned. Your vet may need to sedate the horse to do this.
While appropriate washes can work well if given at least 15 minutes to soak in, this is not always appropriate in mid-winter. Check with your vet that you are using the best antiseptic treatment so as to avoid traumatising the skin or chilling your horse.
Ref: Horse & Hound; 11 December 2014
