Sweet Itch – the Scourge of Summer
By Mic Rushen
Sweet Itch is one of those dreadful diagnoses most horse owners hope never to hear, yet it is becoming more and more in common in all types of horse and pony throughout the UK. Possibly as a result of global warming, midges seem to be prevalent virtually year round in some parts of the country and as a result thousands of equines suffer from Sweet Itch, an allergy to midge bites.
Sweet Itch, being an allergic reaction, points to a problem with the immune system, and these are notoriously difficult to deal with. Horses react to the saliva in the bite of the Culicoides midge (and to a lesser extent the bite of the Simulium Equinum, a member of the blackfly family). The horse’s immune system over-reacts to the harmless proteins in the saliva and effectively the horse "attacks" it’s own cells, causing the cell damage which leads to the awful itching known as Sweet Itch.
Midges are tiny creatures which breed in wet areas or moist vegetation. Only the females are blood feeders – the males feed on nectar. They are not strong fliers, and do not fly in brisk wind, heavy rain or bright sunshine, and they do not like hot, dry weather, but the falling wind and dull light of dusk and dawn suits them perfectly and they are most active then. However, they may feed at any time of day on cloudy, humid days. Their larvae are able to survive severe frosts but they cannot cope with prolonged drought. They are most prevalent in Spring, Summer and Autumn, but may also be around on warmer winter days when the temperature rises about 12 degrees Centigrade and the wind speed is less than 4mph.
Any breed or type of horse or pony may suffer from Sweet Itch, from Shetlands to Shires, though it’s rare in Thoroughbreds. It’s found throughout the world, wherever conditions suit the midges, and is known as Summer Eczema in Europe, or Queensland Itch in Australia. There is a high rate among horses imported to the UK from Iceland, as there are no Culicoides midges present in Iceland so the horses do not develop immunity to the allergy – however, the rate is thought to be no greater among Icelandic horses bred outside Iceland than in any other breed.
It’s not yet understood why some horses get Sweet Itch while their field mates are fine. Some people believe stress may be a contributing factor, or environmental triggers such as pollution. There is some thought that there may be a genetic component, and research is continuing in that area. There are also several Sweet Itch trials underway which are investigating cures for Sweet Itch. So far, though, there is no real cure. The good news is that at least it’s not contagious.
Equines with Sweet Itch suffer from extreme itching, hair loss, skin thickening and dandruff. Severely affected horses may develop bleeding sores, which may become infected if left untreated. Often, midge bites will weep yellowish serum and form crusty scabs. The mane and tail are most commonly affected, though the neck, flanks, withers, hips, ears, forehead and around the eyes may also show symptoms. In some cases, the entire face, along with the legs and belly, sheath/udder area and even the saddle area may suffer. The horse will constantly swish his tail and will attempt to rub vigorously on anything available. He may roll, or rub his belly on the ground. If he has nothing to scratch on, he may bite his own legs and remove his mane with his own hind feet. He will also encourage vigorous mutual grooming from field mates and may damage them in the process. He may constantly pace, become depressed, lack concentration and start head shaking when ridden. Affected skin may become thickened and ridged, and scarring may occur.
All in all, it’s miserable for your horse. And there’s no cure.
So what can you do?
The main thing is to make your horse comfortable and prevent him being bitten by the midges.
First of all, try to avoid keeping your horse in or near areas where midges breed. Still water (lakes, ponds, slow-moving rivers, even large puddles or stagnant water containers), boggy areas, hedges, woods etc are all great for the midges. Ideally, keep your horse in an exposed field with good wind - of course, this is not practical for many horse owners.
Stabling at dawn and dusk will help, but if midges are around at other times your horse will still be bitten. Also, if a stable is at all damp, with a large door and/or open windows, the midges may find your horse there and bite him anyway. Put up a mesh screen across the door, or install a ceiling-mounted fan to keep the midges out. On welfare grounds, it’s not good for your horse to spend hours in the stable, and stabling will only really help the less severe sufferer. Also, an itchy horse will find it very easy to rub in the stable and may get into the itch-scratch-itch cycle which is horribly difficult to break even if you remove the allergen which caused the original problem.
Use insect repellents religiously. Make sure the one you choose is effective against midges, not just flies – most of the really effective insect repellents contain DEET which has a long and highly-effective track record. Nettex Stop-Itch is one example of a fly repellent made for horses which contains DEET.
Use insecticide. Some horse owners find Benzyl Benzoate (or products containing it) works well; however, some horses may react quite badly to it, and become even more itchy. The same goes for some "natural" products containing, for example, Tea Tree Oil or Citronella. Permethrin-containing insecticides (such as the pour-on ‘Switch’) are longer lasting and may be effective. Oil or grease based products may help as midges dislike contact with them. From vaseline, through to baby oil, essential oils and proprietary products, they may work in the short term but unfortunately they do not last long and will be lost through sweating or rain, and you may need to re-apply them at least two or three times a day. Some products will ease areas which are already itchy, for example Sudacrem (a baby product for nappy rash) can really help calm down itching.
Always do a patch test with any insect repellent or insecticide to make sure the cure is not worse than the disease – many horses with Sweet Itch react badly to the ingredients of some products, even the ‘natural’ ones.
Little things may also help – for instance, keep your horse clean and well-groomed. Bath him once a week (weather permitting) in a non-allergenic shampoo. If he is sweaty after riding, hose him lightly to remove sweat. If his skin is dry and scaly, apply an oil-based product such as baby oil. Don’t make rubbing too easy for your horse – use electric fencing to keep him away from trees, posts and rails (and of course to keep him away from barbed wire, which is a disaster waiting to happen for any horse, and is even worse for an itchy horse who will rub on literally anything . . .)
In very severe cases, it may be necessary to administer long-acting corticosteroids which will suppress the immune system enough to stop the symptoms of Sweet Itch. This usually works quite well, but obviously there are side effects when steroids are used, one of which is that horses and ponies are more prone to laminitis so this should be avoided in any susceptible animal. Antihistamines may help, but when given in doses large enough to be effective they usually cause marked drowsiness in horses.
By far the best method of controlling Sweet Itch is to prevent the horse being bitten by the midges in the first place. There are now many different sorts of rug and blanket on the market which offer claim to offer protection against midges. The most effective are made from fabric which the midges cannot bite through, rather than mesh (which is fine against flies but does not deter midges), and cover the horse all over including his belly and neck.
If you are buying a rug for an itchy horse, make sure you buy a dedicated Sweet Itch rug rather than simply a fly sheet. Sweet Itch rugs usually have elastic around the legs and a fitted belly cover to prevent midges flying up underneath the rug. The rug will need to be worn 24/7 in all weathers to be effective. Remove it when you ride and apply insect repellent. The best rugs are comfortable for your horse and he should not be rubbed, or overheat in hot weather. Proper Sweet Itch rugs can be worn in the stable, or can be fitted under a waterproof rug should your horse be chilly in the Spring and Autumn.
Horses which suffer from Sweet Itch on their faces or ears will also need to wear a hood. There are many sorts available, but make sure there is not a gap between the rug and the hood or the midges will get in. You will find hoods with mesh and with fringes – mesh seems to work best for severe sufferers. The best hoods cover almost the entire head including the ears and reach almost to the nostrils – rugs and hoods do not look glamorous, but at least you can be sure that your horse is happy and protected inside them.
For the best results, any midge control program (whether it be stabling, applying insecticides, moving to a windy field, fitting a Sweet Itch rug, or any combination) should be started before the midges appear in the Spring. Once your horse starts itching, it will take two or three weeks for damaged skin cells to recover and for the itching to subside.
The good news is that with the proper care, Sweet Itch can be managed, and your poor itchy horse can once again come through the summer with a nice full mane and tail.
Mic Rushen is the director of Solva Sweet Itch Solutions Ltd (www.solva-icelandics.co.uk), a small company which sells Sweet Itch rugs imported from the Netherlands. . She is an Icelandic Horse breeder and judge, and has many years of experience in managing equines with Sweet Itch. She currently has 11 itchy horses on her farm in Pembrokeshire and is looking forward to a cure finally being found.