Sweet Itch in Horses
Lauren Manzor BVMS MRCVS
Sweet Itch, or Summer Seasonal Recurrent Dermatitis (SSRD) affects approximately 5% of the horse population in the UK and is seen in all types of horses.
Clinical signs of the disease include severe itching, hair loss, skin thickening and flaky dandruff. If the condition is not treated, a secondary bacterial infection may ensue. The top of the tail and the mane are most commonly affected but signs in other areas can be evident in severe cases.
SSRD is an allergic reaction. It is a hypersensitivity reaction to the saliva of the “midge” or Culicoides fly when the horse is bitten. The horse’s immune system overreacts and the horse inadvertently attacks some of it’s own skin cells causing severe itchiness.
Understanding the fly’s environmental preferences can help you to control the problem in equine sufferers.
- Flies prefer moist, humid environments so keep horses off of low lying pastures which are poorly drained
- Hill fields where there are stronger breezes are preferable as midges are too weak to fly against stronger winds
- Avoid turnout in early morning and at dusk when midges are more active
- Fans can prevent flies entering the stable
There are two methods of treating sweet itch – prevent the midge bites and treat the clinical signs. Try to implement as many control measures as possible – use a multi-modal approach:
- Organise turnout as detailed above
- Boet rugs
- Permethrin based fly products (VetPlus’s Switch)
- Oil based applications (Neem oil, Avon Skin So Soft bath oil diluted 50:50 with water) prevent midges from biting skin
- Benzyl benzoate products (Carr Day and Martin’s Kill Itch) help to sooth itch
- Steroids reduce inflammation but can have side effects such as laminitis
- Anti-histamines may help to stabilise the mast cell response but do not work for every horse, must be given in high doses, and may make horses sleepy
- Cavalesse (Findavet) moderates excessive immune response by reducing histamine release in the skin – must be started well before the midge emerges
- Vaccination may become available in years to come and is currently being trialled
- Antibiotics are used to treat secondary skin infections in severe cases
Owners and vets alike can find coping with sweet itch to be very frustrating as there are many treatments but none that are 100% successful. Cases are reviewed individually to try to provide relief from the symptoms affecting each horse.