Sweet Itch Strategies

The Problem

Sweet itch affects around 5% of equines in the UK and numbers are rising. Clearly climate change plays a role in this as do changes in diets which can affect a horse’s susceptibility. Basically sweet itch is an allergy reaction to the saliva in the bite of the Culicoides midges, the female Culicoides bite animals because, like mosquitoes, they need a blood meal to reproduce.

These midges, and in fact most biting insects, are attracted to sweet perspiration, which is why mares tend to be more troubled than stallions or geldings. However modern feeding methods have rendered this point more obscure because most horses today are fed too many sweetish things which reflect in their sweat. This may well be the cause of the increase in the incidence of sweet itch lately.

The bite of the Culicoides midge is very acidic and radically alters the pH of the blood at the site of the bite. This causes irritation to the nerve endings at the skin and fires off signals which let the horse’s brain know that it is under attack. The irritation is quite long lasting causing real pain to the horse and a strong allergic reaction can develop. You know yourself, for example, that if you are bitten by ants the formic acid in their bites can sting like hell, so you can imagine what it feels like to horse when a much deeper and more acidic midge bite is inflicted.

Know your enemy

During the summer Culicoides midges develop from egg to adults in about two weeks. Some larvae and pupae overwinter in protected breeding places and develop as the weather warms up, but most survive as eggs. The species undergo a complete metamorphosis from egg to nymph to adult, and the adult form lives for between 20 to 90 days depending on the weather and the breeding conditions.

The adults fly and copulate in swarms and the female midges require a blood meal for the maturation of their eggs. The eggs need a humid atmosphere and lots of organic material to develop. They usually take about 15 days to reach the adult state.

So, midges breed in damp moist conditions in damp muddy areas, in faecal matter and plant matter.

Sweet itch is closely related to the biology of midges and is therefore a seasonal affliction generally observed in summer and autumn, continuing until the first hard frosts.

What to do

There are several steps you can take to avoid sweet itch and there are others you can take to counter its effects.

 As regards avoidance, you can graze your horses in dry, windswept hills and fields where the midges venture less often.

 You can graze them on chalk which because it drains well denies moisture to the midges often preventing them from becoming a pest.

 You can graze them at night when the midges are inactive and keep them in well ventilated screened stables during the day.  You can also drain all the boggy areas on your land, remove all the manure, trim all the greenery in the hedges, do all you can to establish a constant airflow and lots of sunlight.

These measures will all help in avoidance to a greater or lesser degree but where horses graze you will always get some midges.

Earlier we saw that only a relatively small percentage of horses get sweet itch which is odd because all horses get bitten at some time or other by midges; so you would expect them all to get it. The fact that they don't and the fact that once they have got it they are always susceptible to it thereafter, points to a small proportion of horses. Sweet itch isn't contagious but if a premises is particularly midge infected then all horses in the group can develop the condition. This points to the fact that all horses / equines are susceptible to a greater or lesser extent to sweet itch and can get it (a) if the midge count is very high and (b) if some other unknown factors are present.

Other factors - Let us examine these other factors:-

Almost all equines in captivity are kept in what to them are unnatural conditions i.e. conditions they are not evolved to tolerate well. The main one of these is that their range is often limited so they can't move far away from midge infested areas. They can't easily drift up the hill to windy areas on warm days and so can't easily avoid the swarms of flies and midges which tend to stick to the lower damper areas.

The second factor is stress. Horses today often have to live cheek by jowl with other horses they don't get on with very well. They also often have to endure crowded or what to them are cramped conditions. They often have to travel by road and are also often asked to perform what to them are unusual tasks. All these factors can stress them out and stress reduces the effectiveness of their immune response.

The third factor is food. Many equines today are kept on very rich diets. Feeds that contain sugar beet, molasses, barley and so forth, all have the effect of altering the acid/alkaline (pH) relationship in the horses’ systems. This critical balance means the difference between full good health and an ‘off colour’ immune system less able to fend off the midge bites. If the horse’s bloodstream is carrying too much sugar and is too sweet then it is too acidic and cannot fully counter the effect of the midge bites as it would if it were fully healthy (that is slightly alkaline). The natural alkalinity of the bloodstream of a healthy horse is more than a match for the acidic midge bites!

There is yet another factor which militates against the feeding of too many rich or sweet foods to horses as follows:- When a horse is fed in this way its sweat becomes sweeter, that is it contains more sugar. This sweetness attracts midges to that particular horse more than others in the neighbourhood which is why one horse, usually a mare, gets bitten or at least suffers more than the others in the group. This is probably the underlying reason that this ailment is called sweet itch.

How to manage it

In its natural state a horse’s healthy system is slightly alkaline, its perspiration is naturally slightly sharp, and its skin distinctly non-sweet that is to say alkaline. Because of this natural systemic protection healthy horses in their natural state do not suffer from sweet itch (unless they have some other serious malady first). You should strive, when feeding, to only use high-energy feeds when your horse is going to be working hard. To do so at other times is asking for trouble and doing your horse no favours.

Try and keep the skin slightly alkaline! This can be achieved in two ways - firstly by using a product called Fine Fettle™ Fly-Spray which, sprayed onto a horse’s skin, adds a naturally alkaline factor to the affected area. It is also pretty good at soothing bites and calming itchy horses. The second and more permanent way is to add Happy Tummy ™charcoal to your horse’s feed daily. This redresses the acid/alkaline balance in the hind gut by adsorbing the endogenous toxins that derive from a too rich diet. This very effectively returns the horse’s system to a normal, slightly alkaline state, helping it to withstand the acidic fly bites. There’s no such thing as ‘bitter’ itch so help your horse stay healthy by making its sweat naturally balanced. More information is available at www.finefettlefeed.com .