Sweet Itch

What is Sweet Itch?

Sweet itch is a distressing condition suffered by many thousands of horses and ponies. It is thought that around 5% of the horse population in the UK is affected.

Sweet Itch is an allergic reaction to insect bites (Culicoides midge and, to a lesser extent, the larger, hump-backed Simulium Equinum, a member of the blackfly family) and results from an over-vigorous response by the animal's immune system. This results in severe itching (pruritis) which often leads to hair loss and in severe cases can lead to open sores which in turn can become infected creating new issues.

When the midge lands on the target animal, it secretes saliva to aide feeding. In the process of repelling invading insect saliva (which actually contains harmless protein) the horse attacks some of its own skin cells 'by mistake' and the resulting cell damage causes the symptoms described as Sweet Itch.

Culicoides midges usually feed along the dorsal surface (back) of the horse including the head, mane, withers, rump and dock (tail) and clinical signs are often first seen in these areas. Culicoides numbers are the critical factor in attacks and during a humid evening in the peak of summer a horse may be bitten hundreds of times with each midge feeding for up to 20 minutes.

When does it occur?

It primarily occurs from March to October but symptoms may persist during the winter months. The summer months are particularly difficult for sweet itch owners with many treatments deployed to reduce or prevent suffering during this time.

What horses and ponies are affected?

Native type ponies appear to be more prone than thoroughbreds which may indicate a genetic influence. Horses which have been imported from outside the UK and Ireland may also be more prone as it is believed they have no resistance to the UK flies. Horses will generally develop sweet itch between one and five years old but it can develop in more mature animals where stress is thought to be a contributing factor.

What are the Symptoms?

• Severe itching (pruritis) which often leads to hair loss and in severe cases can lead to open sores.
• Itching normally occurs around the mane, top of the dock, neck, withers, ears, forehead, hips and midline of the belly.
• Sufferers will try to scratch on any object or seek mutual grooming from field companions.
• If there isn't anything available to scratch on, sufferers will persist using their hind feet or can drag themselves along the ground for comfort.
• Sweet itch is not contagious.

Is there a cure?

There is no known cure for Sweet, seen as a vice, it can be managed but does require extra effort.

Click here to read more about managing the condition.

Last Updated: May 2014