Tuesday, 10 February 2015

Sweet Itch - Fidget's Summer Trial!

 It may seem early, but it is about now that I start to think about Fidget and his Sweet Itch.  As the days get longer and the weather improves it could be as little as 3 weeks before he starts suffering.  Fidget didn't have any problems when I first had him but began to scratch his tail probably about 10 years ago.  It has gradually got worse over the last few years as he has got older.  Now, if he didn't have his special rug, he would rub his tail, rump, face, body and mane raw!  It can be distressing to witness as an owner as well as horrendous for the horse or pony,  as you can't stop them rubbing but you know it won't make it any better!

What is Sweet Itch?
Sweet Itch, is a problem that affects thousands of horses, ponies and donkeys in many countries of the world to a greater or lesser degree. It causes misery, stress and injury and can worsen with age. It can affect almost any breed or type of horses, ponies and donkeys. About 5% of the UK horse population is thought to suffer.

The Symptoms of Sweet Itch
The symptoms can include severe itching, hair loss, skin thickening and flaky dandruff. Exudative dermatitis [weeping sores, sometimes with a yellow crust of dried serum] may occur. Without attention sores can suffer secondary infection.
The top of the tail and the mane are most commonly affected. The neck, withers, hips, ears, forehead and around and below the eyes can suffer. In more severe cases, the mid-line of the belly, the saddle area, the sheath or udder and the legs may also show symptoms.

The horse, pony or donkey may swish its tail vigorously, roll frequently and attempt to scratch on anything within reach. It may pace endlessly and seek excessive mutual grooming from field companions. When kept behind electric fencing with nothing on which to rub, sufferers may scratch out their mane with their hind feet and bite vigorously at their own tail, flanks and heels. They may drag themselves along the ground to scratch their belly or sit like a dog and propel themselves round to scratch the top of their tail on the ground.
There can be a marked change in temperament – lethargy with frequent yawning and general lack of ‘sparkle’ may occur, or the horse may become agitated, impatient and, when ridden, lack concentration. He may become hyper-sensitive to any flying insect. 

Diagnosis is not usually difficult – the symptoms and its seasonal nature (spring, summer and autumn) are strong indicators. However symptoms can persist well into the winter months, with severely affected cases barely having cleared up before the onslaught starts again the following spring.

Horses that develop Sweet Itch usually show some signs of the disease between the ages of 1 and 5 years although there is some evidence that stress (e.g. moving to a new home, sickness, castration or severe injury) can be a factor when more mature animals develop the condition. It is common for the symptoms to first appear in the autumn, although they may be fairly mild at this time and could go unrecognised.

Sweet Itch is not contagious, although if conditions are particularly favourable to a high culicoides midge population, more than one horse in the field may show symptoms.

Cause and Culprits of Sweet Itch
Sweet Itch is an immune system problem, which results in an allergic reaction. The disease is a delayed hyper-sensitivity to insect bites and results from an inappropriate response to their saliva, which actually contains harmless protein. Skin cells are attacked ‘by mistake’ and the resulting cell damage causes the symptoms described as Sweet Itch.

In the UK several species of the culicoides midge and, to a lesser extent, the larger, hump-backed simulium equinum, a member of the blackfly family, are responsible. Each has a preferred feeding site; culicoides tend to be body feeders and the simulium ear feeders.

Culicoides adults mainly rest among herbage and are most active in low light and in calm conditions. Their breeding sites are commonly in wet soil or moist, decaying vegetation. They are tiny, with a wing length of less than 2 mm and are only able to fly a short distance (100 metres or so).

Male culicoides feed on nectar, but soon after hatching the females mate and require a blood meal to mature their eggs. The larvae are able to survive extreme cold but they can be desiccated by prolonged summer drought. The adults do not fly in strong wind, heavy rain or bright, clear sunshine. They dislike hot, dry conditions. The grey light at dusk and dawn suits them well, and they are at their most active at these times. 

However, as they are poor fliers, if there is too strong a wind, or rain during early morning they will simply wait until later to feed. Likewise they may feed at any time during humid days with cloud cover.

Culicoides are on the wing and breeding from as early as March until early November, depending on geographical location. There is only a short breeding season each year in the north of Scotland, while in the south of England larvae will hatch throughout the spring, summer and autumn, depending on weather conditions. Seasonal variations in the weather can have an impact – milder and damper winters allow breeding to start earlier. Summers that are alternately sunny and rainy cause an increase in midge breeding habitats and therefore an increase in the numbers of midges that are around to bite. Under these conditions most horses will show symptoms of Sweet Itch to some degree. Culicoides numbers are the critical factor!

How to manage Sweet Itch
At present there is no cure for Sweet Itch. Once an horse, pony or donkey develops the allergy it reappears every spring, summer and autumn.  Their comfort and well being is down to how its owner manages the problem. 

Minimise Midge Attack

  • Avoid marshy, boggy fields. If possible move the horse to a more exposed, windy site, e.g. a bare hillside or a coastal site with strong onshore breezes. Chalk-based grassland will have fewer midges than heavy clay pasture.
  •  Ensure pasture is well drained and away from rotting vegetation (e.g. muck heaps, old hay-feeding areas, rotting leaves).
  • Stable at dusk and dawn, when midge feeding is at its peak, and close stable doors and windows (midges can enter stables). The installation of a large ceiling-mounted fan can help to create less favourable conditions for the midge.
  •  For slight to moderate cases of Sweet Itch this can help. However a seriously itchy, stabled horse has hours of boredom during which to think up new ways of relieving his itch – manes and tails can be demolished in a few hours of scratching against a stable wall. If stabling can be avoided it is best to do so.
Use an Insect Repellent.
  • Effectiveness varies, so it is best to try a variety and then stick with the most effective.
Use an insecticide.
  • Some owners achieve good results with insecticides whilst others find they have shown little benefit in controlling Sweet Itch.
  •  Benzyl benzoate was originally used to treat itch-mites (scabies) in humans and has been used for many years to combat Sweet Itch. In its neat form it is a transparent liquid with an aromatic smell, but it is more commonly obtained from Vets or pharmacies as a diluted milky-white suspension. It is listed as an ingredient in several proprietary formulations, including Carr & Day & Martins’ ‘Killitch’. Benzyl benzoate should be thoroughly worked into the skin in the susceptible areas every day. However it is a skin irritant and should not be used on the horse if hair loss and broken skin have occurred – application should therefore start before symptoms develop in the spring. If used later its irritant properties can cause areas of skin to slough-off in the form of large flakes of dandruff.
  • Other insecticides, including permethrin and related compounds, tend to be longer lasting but should also be used with care. Permethrin is available by veterinary prescription (e.g. Day, Son & Hewitt ‘Switch’ pour-on liquid). Application instructions should be followed.

Note: Gloves should be worn when applying insecticides, including benzyl benzoate. Particular care should be taken if they are used on ponies handled by children – they can cause eye irritation, for example if fingers transfer the chemical from the pony’s mane to the eyes.
Other Options
  • Oils & Greases – Coat the susceptible areas of the horse with an oil . Midges dislike contact with a film of oil and they will tend to avoid it. Commonly used preparations include Medicinal Liquid Paraffin, and ‘Avon Skin-so-Soft’ bath oil (diluted with water). There are several oil-based proprietary formulations, for example Day Son & Hewitt’s ‘Sweet Itch Lotion’.
  • Oils and other repellents that are effective usually work for a limited time: In summer a horse’s  short coat-hair does not retain the active ingredient for long and it can be easily lost through sweating or rain. Re-application two or three times every day may be necessary.
  •  Greases (usually based on mineral oils) stay on the coat longer, but they are messy and therefore not ideal if the horse is to be ridden. They can be effective if only a small area of the horse is to be covered. However it is impractical and often expensive to cover larger areas.
  • Some preparations contain substances (e.g. eucalyptus oil, citronella oil, tea tree oil, mineral oil or chemical repellents) that can cause an allergic skin reaction. Always patch test first on the neck or flank of the horse – apply to an area about 3 cm across and look for any sign of swelling or heat over a 24 hour period before using more extensively.
  •  BioPlus Capsules - they may help your horse.
  •  Allow Midge Attack, but try to minimise the resultant allergic reaction by: Depressing the immune system with cortico-steroids (e.g. by injection of ‘Depo-Medrone’ or ‘Kenalog’, or in tablet form as ‘Prednisolone’) may bring temporary relief, but there can be side effects, including laminitis, in some animals. With time, corticosteroids may become less effective, requiring ever larger and more frequent doses.The use of anti-histamines may bring some relief, but high dose rates are required and they can make the horse drowsy.
  • Applying soothing lotions to the irritated areas. Soothing creams such as Calamine Cream or ‘Sudocrem’ can bring relief and reduce inflammation, but they will not deter further midge attack. Steroid creams can reduce inflammation.
  • Use a sweet itch rug -This is by far the most effective Sweet Itch protection to date and avoids the need to use insecticides, oils or greases. If used early enough in the year this can prevent the horse, pony or donkey developing any reactions and with annual use you may find that the suffering reduces over time.

This was Fidget's first Sweet Itch rug, designs have improved.

I found with this rug that he rubbed his eye area as that wasn't covered, it was also hot in the heat of the day!

The day we tried on his new and current rug!

My experience is that there is no substitute for a good rug, if I put it on early enough in the Spring Fidget scratches far less.  Unfortunately I do feel that to some extent he has formed a scratching habit - but this is still improving.  He does still suffer in the areas not covered, so inside his back legs and around his sheath.  For these areas I try creams and lotions but so far have not found anything particularly effective!  It is a running battle every year to make him as comfortable as possible and I do think we are slowly winning!

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