Sweet itch is one of the most difficult skin conditions to control. Caused by an allergic reaction to midge bites, there is evidence that the problem is getting worse as the effects of global warming have extended the period of the year when midges are active. Affected horses that used to be assured of a symptomless winter are now in many cases suffering for most of the year.All breeds from Shires to Shetlands are affected. There is now ample evidence that susceptibility to the disease is inherited so affected individuals should not be bred from. The problem can start at an early age, even as a foal, and each year the itching of the face, mane, topline and dock areas gets progressively worse. In some cases the underside of the belly is also involved.
We would not recommend buying an affected horse unless one is prepared to make a major commitment in time, effort and expense to control the problem.
How can the disease be controlled?
Control relies upon
- Preventing the midges from landing on the horse by providing a physical barrier or applying an insect repellent. The barrier may comprise a rug or an oily film applied to the coat
- killing the midges after they have landed but before they have had a chance to bite, or
- keeping the horse or pony indoors when midges are active
Undoubtedly the best control method is to use a sweet itch rug. While a cotton summer sheet will provide some protection, not enough of the body is covered. A purpose-made sweet itch rug comprises a head and neck part, a wide belly part and a body part that extends to completely cover the dock region also. Because midges are quite tiny the mesh size needs to be extremely small. For this reason anti-fly rugs are not usually adequate.
Examples of the available sweet itch rugs are
- Snuggy hoods www.snuggyhoods.co.uk (01225 783399)
- Boett Blankets www.sweet-itch.com (01352 771718)
- Rambo Sweet Itch Hoody www.horseware.com
- DeMeulenkamp rug www.solva-icelandics.co.uk
Sweet itch rugs should not be used if the pony is already rubbing, as they will ruin the rug in a matter of days. Once you have obtained the rug and before you use it, it is best to ask us to administer a short-acting cortisone or antihistamine treatment in the first instance to eliminate the symptoms.
If in spite of rugging the pony is still itching it suggests one of the following has happened
- The rug was first used while the pony had active disease. Sweet itch may take a long time to subside and drug treatment is usually advisable
- The mesh size is too large
- Not enough of the body is covered. It will be necessary to use an insecticide (see below) on the exposed areas.
What about insecticides?
A second-best approach is to apply an insecticide to the susceptible areas of the body. These are often prepared in an oily vehicle to provide an additional barrier. Benzyl benzoate is the traditional remedy and is the ingredient of most proprietary sweet itch preparations. Pyrethroid insecticides such as 'Deosect', 'Coopers Fly Repellent Plus' and 'Barricade' are useful but the concentration must be increased and they must be applied every day. 'Switch' is a concentrated insecticide applied weekly. 'Frontline' dog flea spray applied weekly has also been reported to be effective but is expensive.
There are a huge number of proprietary anti-sweet itch skin lotions and creams available. Most are combinations of repellents and insecticides. The most effective repellent is DEET. They must be applied generously (on the face and dock, and extending about a foot [30cm] either side of the spine) and at least daily. Experience suggests they are rarely as effective as a sweet itch rug, but one product 'Stop Itch Salve Complete' can be used in combination with a rug to protect the areas not covered by the rug, for example the face and dock.
Insecticides are much more effective if the mane is hogged and the dock is trimmed or pulled short, and they must never be applied to inflamed skin. In general simple fly repellents are useless as they are far too short-acting.
Other approaches
Stabling the pony during the periods of midge activity (dawn and dusk) is useful. The pony should be turned out no earlier than 10am and brought in before 3pm. Turning out after dark is not a good approach because the pony must be brought indoors before first light, which might be 4-5am in the summer! Midges will readily enter stables although old net curtains hung over the doors and windows will keep them out. Midges don't like windy conditions so strong fans in the stable will inhibit their activities.
Environment. Sweet itch-susceptible horses are best keep in exposed fields well away from damp sheltered areas where midges breed.
Feed supplements. There are a myriad of dietary supplements that may aid control but will never be sufficient on their own. Garlic added to the feed has many devotees and there is some recent research evidence from Canada that adding linseed to the diet reduces the irritation resulting from midge bites. This can be in the form of cooked linseed or feed-grade linseed oil (less palatable)
Homeopathic remedies have in general been disappointing although more recently there have been claims of successful control using a homeopathic midge extract (Equus Health 01208 821758).
Veterinary treatments
Drug treatment, principally using cortisone and more recently antihistamines, should be reserved either for situations in which short-term treatment is necessary to eliminate symptoms while other methods are sorted out, or in situations where the owner is not able or willing to use other approaches. Cortisone has given rapid relief to many badly-affected miserable, ponies. However long-term cortisone treatment carries a risk of inducing laminitis and should only be used as a last resort.
Desensitisation
Desensitisation is an immunological approach to control. The aim is to induce blocking antibodies which prevent the sweet itch inflammatory response from occurring. Unfortunately the treatment is expensive, requires multiple injections, has produced mixed results and takes a long time to work. We do not recommend it at present although there may be developments in this area in the future.
‘My pony is rubbing its mane and tail. What should I do now?’
- Get the pony indoors straightaway and keep it indoors until the symptoms can be brought under control
- Contact us for advice. We will confirm the diagnosis and review with you the most appropriate control methods for your situation. We may in addition give the pony some drug treatment to bring about rapid resolution of the symptoms while the long term management is changed.
DISCLAIMER
This factsheet is intended for use by registered clients of EqWest only. The advice offered is general advice only. EqWest clients who wish to discuss the individual circumstances of their horse should contact the Clinic.
To speak to a vet please phone between 8.30 - 9.30 am on weekday mornings.
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