What is Sweet Itch?
Sweet Itch is an allergic skin condition causing horses and ponies to feel very itchy and uncomfortable. It is more common in ponies and the condition can be hereditary. The disease can be very disfiguring.
What causes Sweet Itch?
Affected animals are hypersensitive to the saliva of the biting Culicoides midge. There are over 100 species of this midge. Some horses develop a similar allergy when bitten by stable flies (Stomoxys spp.) and black flies (Simulium spp.).
What are the symptoms of Sweet Itch?
- Affected animals rub themselves against trees, fences and stables in an attempt to relieve the irritation.
- The condition varies in severity from occasional rubbing with some broken mane and tail hairs to almost complete loss of the mane and tail. Initially the horse or pony has patches where the hair has obviously been rubbed. This may progress to bald patches or weeping sores.
- Lesions occur most commonly on the face, forelock, poll, mane, neck, withers, rump, tail head and dock. Some animals experience irritation along the ventral midline especially on the soft skin in front of the udder or sheath.
- Secondary bacterial infections can develop.
- With time, the repeated trauma causes thickening and ridging of the skin at the base of the mane, especially near the withers.
- Some ponies are so bothered by the condition that their behaviour becomes erratic and unpredictable. They can be miserable and bad-tempered, swishing their tails and kicking their bellies.
The condition tends to be seasonal, with symptoms occurring in the UK between late March and early November when the insects are prevalent. In a mild winter (or warmer climates), a sensitized pony may be affected all year round. The flies are very small and are not strong fliers. They feed less on windy days when the wind speed is more than 7 km/hour (4 miles/hr).
How to prevent Sweet Itch
With horses or ponies that suffer every year, the aim should be to prevent the signs by careful management, rather than waiting for them to develop. This is done by reducing their exposure to the midges.
- The midges breed in standing water and damp, rotting vegetation so wherever possible, the pony should be moved away from these.
- Drainage of marshy fields and ponds may help.
- Any stagnant troughs or water containers near the stable should be removed.
- The flies feed primarily at dawn and dusk and may continue during the night. The pony should be stabled from an hour before sunset until at least an hour after sunrise the next morning. The safest period for grazing is mid-morning to mid-afternoon.
- Screening the stable windows, door and also air spaces that communicate with the next stable with a fine mesh to stop midges entering will help.
- The use of a large ceiling-mounted electric fan may help to drive the midges away.
- When the pony is in the stable or turned out, a special sweet itch rug and fly mask/hood which prevents midges biting and covers as much of the pony as possible affords considerable protection. This is made of a breathable material and can be worn for up to 24 hours a day.
- Regular application of a fly repellent, e.g. pyrethrin, is likely to help.
- Benzyl benzoate may give some relief by making the midges less likely to bite, but it is an irritant and should not be applied to skin that is already broken and sore. Benzyl benzoate is a weak insecticide that requires daily application.
- Oily lotions are messy, but these can provide a mechanical barrier and prevent the flies biting.
- Some owners report an improvement with the inclusion of garlic in the diet.
- If at all possible, affected horses and ponies should be moved to a midge-free area such as an exposed hilltop or breezy coastal site.
These measures should be in place before the start of the midge season.
How to treat Sweet Itch
Treatment to reduce the irritation should be started as soon as the first signs are seen.
Soothing lotions such as Sudocream or aloe vera preparations and sprays can reduce the irritation.
Provided there is no infection, a corticosteroid cream may be prescribed by your vets. Gloves should be worn when applying this and the treatment is only practical for small areas.
If secondary infection occurs, an antibiotic cream may be necessary.
Shampooing the horse every 1-2 weeks to remove the scurf and scabs may help to decrease the irritation. A hypoallergenic shampoo should be used.
If the irritation is severe and cannot be relieved by topical treatment and good management, then it may be necessary for the vet to prescribe antihistamines or corticosteroids. Corticosteroid tablets, e.g. prednisolone, are usually given daily to start with while the symptoms are severe. As soon as possible, the dose is reduced to a minimum and given on alternate days to reduce the risks of side effects which include laminitis and immuno-suppression. Any wound infection should be cleared up with antibiotics before corticosteroids are given. Long-acting corticosteroid injections may help with some cases but these are not recommended as they carry an increased risk of complications such as laminitis.
Treating Sweet Itch Long Term
If the condition is recognised early and the owner has the time and facilities to manage it well, many horses with a susceptibility to sweet itch develop only mild signs with occasional rubbing.
However, in other cases the prognosis is guarded. The disease can be both debilitating and disfiguring. It prevents the animal being used for showing and the sores may limit riding in the summer.
Sweet Itch is costly in time, effort and money. Not surprisingly, affected animals may become bad-tempered and unreliable. The condition tends to get worse each year. Moving the horse or pony to another environment may help. However, there are some ponies who reach a state where no treatment is effective and every summer is a time of torment and misery. In these cases, euthanasia may have to be considered.