What is sweet itch?
Sweet itch is an allergic reaction to bites from mosquitos and midges which can affect almost any horse or pony - regardless of type, breed and age – but research does show it is particularly prevalent in some native breeds. Sweet itch is the most common allergic skin disease in the UK and affects around five per cent of our horse population.
The types of midges and mosquitos which cause the hypersensitivity differ depending on the country but in the UK these are the black fly (Simulium) and the midge (Culicoides). It is also worth noting that whilst we tend to think of sweet itch as a summer condition, these biting insects are active from March to November.
The itchiness associated with insect bite allergies can be termed pruritis and the term ‘sweet itch’ quite literally describes the sensation experienced by the horse or pony in reaction to bites from mosquitos and midges. The condition varies in severity from the horse occasionally scratching his tail on a tree to the very worst cases who will scratch and scratch, causing self-trauma. A lot of cases will also have secondary infections or other allergens involved.
Whilst not life-threatening as such, we must not underestimate the suffering which sweet itch can cause the worst affected horses and ponies.
As such, it’s important to be vigilant to any sign of sweet itch as early diagnosis and treatment will give a much better chance of being able to manage it effectively. If your horse or pony is beginning to show any signs of scratching, the first thing is to ascertain whether they are actually suffering from sweet itch. There are many other allergens with the same or very similar clinical signs as sweet itch but may not be caused by midges.
What are the symptoms?
Symptoms of sweet itch will vary widely from horse to horse. Some will be severely affected by just one or two bites, whilst others may experience no reaction at all.
- Itching will often be focused on the neck, mane and tail, but these areas are not at all exclusive and the worst affected horses may end up rubbing and biting at their skin wherever they can reach.
- Affected areas will appear lumpy or scaly and usually inflamed or hot to the touch, but you may also just notice areas where the hair appears ruffled and rubbed.
- Self-trauma from scratching may cause hair loss, bleeding and thickening of the skin.
- Skin may also look scurfy or dull in patches so this is another thing to look out for, although it is a symptom which could indicate a different condition.
- Some horses can become restless and in the very worst cases may even start to lose weight as a result of the condition.
Grooming your horse regularly is a good way to keep a close eye on his skin so you can recognise any changes and take appropriate action quickly – particularly if you have a horse who likes to keep themselves coated in mud which can make it very difficult to spot problems!
How is sweet itch diagnosed?
If you suspect your horse is suffering sweet itch, in the first instance it is worth implementing basic control measures (see prevention and management headings) and if the condition does not seem to be responding then the next step should be to ask your vet to do intradermal allergy testing.
This test will inject midge extracts into the skin to observe for a reaction. This will also detect for other allergens so you can narrow down the potential causes. You may find various blood tests which clam to be able to detect allergies but there is limited evidence to support their use or reliability.
When should you be most vigilant for symptoms?
The mosquitos and midges which cause sweet itch are active between March and November so this is definitely the time to be the most vigilant for any indications that your horse is suffering sweet itch, however this is not the only time period when symptoms may show. Typically, sweet itch will be a seasonal condition but it is common for affected horses to show increasingly severe symptoms over time and so some will experience problems all year round.
What steps can be taken to prevent sweet itch?
When it comes to sweet itch, prevention really is much better than cure and one of the worst things you can do is ignore the early signs.
- Fly-rugs are becoming increasingly sophisticated with a wide variety on the market to suit a range of budgets and also severity of the horse’s symptoms and reaction to biting insects. The worst affected horses will likely need to wear a fly rug 24/7 so it is well worth investing in a rug which is a good fit, is comfortable for the horse and is hard-wearing. You can even purchase fly rugs which are specially designed to fit different shapes or types of horse and pony, but obviously these are likely to be towards the top end of any budget.Some rugs will simply cover the body, neck, tail and under belly area, whilst others will quite literally encase almost every inch of the horse’s skin to ensure as little is exposed to biting insects as possible.
- When it comes to fly repellents, there are a huge number of different types, brands and applications available. A traditional spray or cream application is always a good option but you may also find repellent bands and tags helpful in controlling mosquitos and midges. Look for products with pyrethroid or permethrin-based ingredients as these are often the most effective. DEET is effective but can cause soreness in some horses and Avon Skin-so-Soft can also be an effective, less-chemical option.
- Biting insects tend to be at their most prevalent at dawn and early evening or dusk so if possible, try to keep your horse stabled during these times. This will vary depending on your geographical location, the time of year and what is practical for you as an individual. In an ideal world, you would be able to keep popping back to let the horse out or put them depending on the time of day but obviously work and life commitments can make this difficult.
- You can buy ultrafine (60 squares/inch) midge screens to put over stable doors and windows which can be effective at keeping the insects at bay. This may sound like an extreme option but it is important to bear in mind that sweet itch is a hypersensitivity with added self-trauma (scratching) so even just one or two midges making their way through the defences can cause widespread clinical signs.
- Insecticidal sprays can be helpful to use in the stable area and it can also be worth installing fans too as these will help reduce the midge burden.
- Female midges lay their eggs in the soft mud after feeding so areas with standing water should be avoided wherever possible. Areas that are naturally windswept will have a reduced midge population than sheltered locations where the air is very still. Try to avoid thick tree lines too for the same reason. A paddock on top of a blustery hill would be the absolute best location but clearly is not something many people will have access to. If your field has any particularly low lying or sheltered areas, it may be worth fencing these off so your horse cannot access them.
How can sweet itch be treated or managed?
Unfortunately there is no real cure for sweet itch and it is simply a case of putting measures in place to stop the midges biting wherever possible.
- Steroids can offer relief from the clinical signs (skin irritation and itching) in the short to medium term and can be administered to buy some time in implementing better preventative and management measures to stop the bites. However, over the long term steroids increase the risk of laminitis so this is not a sustainable solution and must only be used if prescribed by your vet.
- In some cases, antihistamines can help relieve the symptoms but must be administered in relatively high quantities, making this an expensive and often ineffective option. Once again, these should only be used if advised by your vet.
- Anti-itch shampoos can be effective to help reduce itching – look for those which contain oatmeal, anti-histamines or local anaesthetics. Another option to offer short term relief is bathing with ice or cold water to cool the affected areas.
- Research has shown that omega 6/3 fatty acids can be effective in reducing itching so it may be worth feeding flax seed or evening primrose oil in case this offers some relief.
- Cavalesse is a supplement containing Nicotinamide which is fed orally and has been shown to be partially effective in relieving clinical signs.
- ‘Itchy Horse’ is an organisation which has replaced the National Sweet Itch Centre and whilst it is a commercial organisation, it does have some partially successful products such as Bioeos capsules.
Different solutions and products will work in varying degrees for different horses so there does have to be some trial and error in order to find what is effective for your horse and your situation.
A combination of preventative measures and taking appropriate action/treatment as soon as any signs develop will help to manage the problem and make life as comfortable for the affected horse as possible.