Sweet Itch

With summer now well underway, horses across the land will be spending more time than ever out of their stables and into open air, where they can enjoy the sunshine. But while this is a season we might associate with prosperity and optimism, it’s also one that carries a few risks for our horses. Among these risks is an unpleasant phenomenon called Summer Seasonal Recurrent Dermatitis, or Sweet Itch. As you might expect, this condition causes the animal to itch – sometimes to the extent that they cause themselves so much damage that they can’t bear the sensation of tack against their skin.

In this article, we’ll take a closer look at this unpleasant condition – and examine how it might be guarded against.

What causes Sweet Itch?

Sweet itch occurs thanks to midges – specifically Culicoides midges. The saliva of these midges contains a protein which causes an extreme allergic reaction in horses. The immune system will attack the skin cells as though it were a harmful pathogen, which causes the itching sensation.

Brown horse biting itself to ger rid of itch
Brown horse biting itself to get rid of itch

While no horse is immune from the effects of sweet itch, some are certainly more susceptible than others. The condition is rarer, for example, in Thoroughbreds than it is in Friesians. Anecdotal evidence also suggests that older and injured horses may be at greater risk of contracting the condition.
Midges need moisture a warmth in order to breed. Consequently, they’re at their most active early in the morning and late in the summer evenings. Horses which graze near marshy areas and large bodies of water, like canals, rivers and lakes, at risk. Indeed, water is arguably a great factor in the midge’s prosperity than heat; their larvae are able to endure through frost, but they’ll quickly perish when a drought strikes.

Sweet itch, as we’ve mentioned, is caused by an allergic reaction rather than a bacterial infection. This means that it cannot be transmitted between different animals. That said, if a horse suffers from the condition, then it follows that other horses who share the environment might also be vulnerable. And if a secondary infection is allowed to develop (we’ll get to that shortly) it might pose a threat to other animals who share the same field.

What are the symptoms of Sweet Itch?

The midges which cause sweet itch typically feed along the back of the horse. You might spot them around the back of the head, the withers, the mane and the top of the tail – with the most intense itching occurring around the latter two. As the condition progresses, the horses’ hair will begin to fall out. The skin will swell up, and dermatitis might set in, causing nasty sores which weep yellow puss.

If you’ve ever had an itch, then you might have scratched it. This helps to relieve the symptoms, but in the long run makes the problem worse. The same effect occurs here; a horse will rub itself against whatever object happens to be conveniently placed – be it a tree, a gate or a fence. Horses will even roll onto the ground and bite their own hooves in order to relieve the sensation.

Leaving to one side the obvious effect that this has on the horse’s skin, it can also bring about changes to the animal’s behaviour. Affected horses may become lethargic or impatient, and they might appear distracted – especially when they’re being ridden. As you might imagine, they’ll also be acutely aware of nearby insects, and may suffer from a lack of discipline as a result.

How is sweet itch treated?

There exist several different methods of treating the symptoms of sweet itch. Among these are oral solutions like Cavalesse, which can be administered during mealtime, and acts as an anti-inflammatory by increasing the production of healthy oils and fats in the skin. These substances help to lessen the itching sensation, and thereby interrupt the cycle. Exposure to cold water (or ice packs) might also lessen the reaction, as might antihistamines – though the latter must be prescribed by a veterinary surgeon.

In some extreme cases, it might be necessary to administer steroids – but doing so will depress the immune system, and therefore may bring about undesirable side effects. However your veterinary surgeon will discuss the pro’s and con’s of such a course of treatment.

But since prevention, as ever, is better than cure, it’s better that we limit the horse’s exposure in the first place. This can be done by relocating horses away from marshy areas to drier ones, which might be exposed to the wind. You’ll also need to ensure that any grazing areas are properly drained, and that that any rotting plant matter is removed. Finally, you’ll want to stable your horses during dusk and dawn, when midges are at their most active, and install protective screens in order to prevent midges from reaching the inside.

Such environmental changes might not always be practical – you might not have a spare, drier patch of grassland to move your horses to. Fortunately, more brute-force solutions provide an effective solution – by covering your horse in a protective rug during the times when midges are a greater risk, they’ll be unable to bite. However, this approach might cause irritation to a horse that’s already effected – and so it should be employed before the problem has a chance to set in.

Since midges are at their most active during the summer, it’s at this time of year that the risk of sweet itch is the greatest. However, changes in climate mean that winters offer warm weather, too – which means that midges can bite all year round. This is particularly so if a complacent attitude towards midges takes hold during winter – so be sure not to let your guard down, particularly during winters as mild as the one we’ve just experienced.

The symptoms of sweet itch might disappear during winter, but they’ll return very quickly when summer comes back. For this reason, it’s wise to be cautious when buying a horse during winter. Be sure to inspect any prospective purchases for evidence of a history of sweet itch – which most often comes in the form of hair loss.

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