Greetings from the far north! With spring well underway, the grass growing and my first AI mare scanned in foal and our local rugby club into the Ravenhill cup final, life is good and the long evenings just make it so much better.

A few weeks ago, I went out to the farm of one of my longest clients to have a look at a six-year-old which had just recently returned from the show jumping establishment where he was being schooled. He was in great form and as he is almost 17hh, I was looking up at him most of the time!

At first the reason for the call was not obvious as the light in the stable was a bit dim. However as I ran my eye over him, I noticed three patches on his back in the saddle area from which the hair had disappeared.

The areas were dry, slightly scurfy and irregular in shape with no hair on them at all. The horse had only come back the previous week and the owner had not noticed anything wrong then. After having a thorough look over the whole of the animal’s body, I came to the conclusion that these were the only lesions and that this was a case of Dermatophytosis or the more meaningful name of Ringworm.

The owner was a bit taken aback but I hastily explained that this is one of the commonest skin conditions and can affect all sorts of animals including dogs, cats, cattle, horses and people. The infection is caused by a fungus which grows on the surface of the skin and it can take from one to four weeks – I usually think of a three-week timescale and this case certainly fitted in to the timeframe.

The other possibilities which would have similar signs would be lice, rain scald or dermatophilis infection, infection of the hair follicles and a few rarer conditions involving a skin mite or a skin form caused by the Onchocerca worm or an allergic reaction.

Lice in horses are very common but we generally see it in the winter when the coats are long and the horse starts scratching. With the intense itching, the coat soon becomes patchy and moth-eaten and the lice can be seen with the naked eye if you look closely enough.

Dermatophilis infection is also known as rain-scald but this horse had been stabled and was therefore not exposed to prolonged wet conditions. Also infections of the hair follicles tend to be more widespread and the skin has a ruffled, unkempt appearance.

Infection with the worm Onchocerca tends to occur during the summer and may be spread by the midge, but routine worming with any of the pastes containing ivermectin, e.g. Eqvalan or the generic forms, makes this condition most unlikely.

Allergic conditions such as sweet-itch must always be considered but again it was the wrong time of year and also the animal was inside for the majority of his stay at the stables.

So after running through the other possibilities, we were left with the diagnosis of ringworm. The fungus is easily spread by the transfer of the fungal spores which are highly resistant to normal disinfectants and may persist for years especially if they get into older houses or wooden fencing, racks or other fixtures in the stables. One lecturer in the vet college advised that to definitely get rid of ringworm spores from a house, you would need to burn it down! Bit drastic in most circumstances but the more modern stables have smoother surfaces and are therefore more easily cleaned. The time it takes for the infection to develop is usually around the two to three weeks but may take up to four to become apparent.

In that time of course the horse will be groomed, ridden or even just being turned out with others for some exercise and the opportunities for the spread of the infection will occur. In fact the contamination of grooming equipment and tack are the main routes by which the disease is spread.

TREATMENT

In the case of this horse, the lesions were quite localised and so I prescribed a wash for him to be applied on four occasions three days apart. I use a product which contains enilconazole and have found it to be effective when used according to the manufacturer’s instructions.

The wash should be applied using a sponge or a soft brush to the affected area and in a wide circle around it. The condition gets its name as it often appears as round patches. Just think of a spot of blue mould growing on a slice of bread – usually a perfect circle as the fungus starts in the centre and grows outwards. Samples can be taken and sent to the laboratory for confirmation but culture of the fungus takes up to three weeks as indicated by the incubation period.

If the coat is long, then it should be clipped but do remember that those clippings will also be infective and should be disposed of carefully or burned. All the tack should be disinfected as well as rugs, brushes and anything that comes into contact with the horse. When the horse’s lesions have been soaked, the remainder of the solution can be used to wash the tack and grooming equipment. The owner also needs to be warned to watch out for any small, red, itchy spots which develop on the hands, arms or other exposed skin and seek medical help. If caught early, those lesions may be successfully treated with antifungal products.

In days gone by, the only available treatment was iodine which at high concentrations I am reliably informed stung like mad when applied to the affected areas! The person involved said he remembers it only too well.

Back to my client’s horse. Thanks to the antifungal wash, the lesions disappeared.

Anne Scott MVB MRCVS is a member of Veterinary Ireland Equine Group and is in practice in Inishowen Equi-ai Centre, Tulnaree House, Carndonagh, Co Donegal

Email: hq@vetireland.ie

Telephone: 01-4577976