Seasonal Ailments
Sweet Itch (SSRD)
Sweet itch is the common name for summer seasonal recurrent dermatitis (SSRD). It is caused by an allergy to the saliva of biting insects specifically the Culicoides midge and, to a certain extent, the black fly.
The disease mostly affects adult horses from April to October and is relatively common although rare in thoroughbreds.
The Culicoides midge likes to live in moist conditions near damp soil and rotting vegetation etc. The black fly prefers slow streams and stagnant water. Both like calm, humid conditions and are most active at dawn and dusk.
SSRD is not a contagious disease. However there are likely to be genetic factors involved resulting in some animals being more prone to the condition. The severity of the symptoms is proportional to the size of the midge attack therefore prevention is based on minimising the number of midge bites.
Symptoms
The disease presents as anything from mild to very severe itching. This then results in self-harm leading to hair loss, thickening of the skin, dandruff, sores and secondary infections. The mane and tail are most commonly affected but in more severe cases it can affect other parts of the body as well.
Clinical signs include swishing of the tail, scratching, rubbing, rolling and pacing around in an agitated fashion. The animal might become restless and tricky to ride.
Prevention and Treatment
Management of the disease is centered around reducing the level of exposure of the horse to the midges. Moving the affected horse to an exposed, windy area with well drained grazing is one way of keeping the animal away from the biting insects. Veterinary advice also includes keeping the animal away from rotting vegetation, muck heaps and ponds or streams and stabling them at dawn and dusk, ie overnight. Closing stable doors and windows is not ideal for their respiratory system but does help to keep the midges away. Alternatively, insect proofing the stable using a very fine mesh and using fans to create a breeze in the stable area will discourage the insects.
Insect repellents alone are not the answer as they quickly wear off. Greasy solutions such as benzyl benzoate applied several times a day will help to prevent the midge from being able to get access to your horse's skin. Probably the most effective way of repelling the insects is the use of light rugs and hoods that offer complete protection from midge bites.
Prevention is always better than cure so try to take precautions before the symptoms become severe. Once the horse has been badly bitten then the symptoms may not resolve despite your efforts to reduce the midge attack. In severe cases the vet may have to consider the use of corticosteroids to relieve the itching and reduce the self trauma. Unfortunately, antihistamines are not of great value in the horse and a vaccine that was recently developed and tested also proved ineffective.
When you buy a horse bear in mind that the symptoms of SSRD can completely disappear in the winter so look carefully at the mane and tail to check for signs of rubbing, thickened skin, broken hairs etc that could alert you to a previous problem.
Laminitis
This is traditionally a spring and summer disease but is now becoming more common throughout the rest of the year.
The word laminitis means inflammation (itis) involving the sensitive laminae of the feet. These laminae are the delicate soft tissue structures that hold the pedal bone in place inside the foot and when they are inflamed the horse suffers considerable pain particularly in both front feet but all four may be affected.
The most common cause of laminitis is obesity. The typical candidate is an overweight pony/cob type that has been allowed to eat too much grass in April/May, is not in work and is consequently continuing to put on weight. Native ponies in the wild live on next to nothing and are not suited to rich pasture. Many modern pastures have been chemically fertilized and are full of nitrogen and sugars. Fructan is the sugar believed to be one of the factors that causes the changes in the hindgut that produce the trigger factors for laminitis.
Metabolically horses and ponies are very different. Ponies and cobs are much more efficient at utilising food and very good at storing fat. These animals should be on a forage-based diet of hay and alfalfa and fed very limited amounts of cereals and mixes.
There are other causes of laminitis that are not related to the time of year. These include any form of toxaemia, trauma to the feet from exercising on a hard surface for too long or simply having badly shaped or poorly maintained feet. Laminitis can also be caused by drug administration (eg corticosteroids), stress and Cushings Disease.
Symptoms
The most common symptom of laminitis is foot soreness, particularly when walking on hard surfaces, and generally both front feet are equally affected. There are many other symptoms including stiffness, lameness, shifting of weight, rocking back on the heels, difficulty turning, reluctance to move, lying down more than normal, increased amplitude of the pulses to the feet, dropped soles, restlessness and sweating. Although many animals with laminitis have 'heat' in their feet this is not a reliable diagnostic indicator as foot temperature tends to vary throughout the day.
Prevention and Treatment
Prevention is centred round controlling the animal's weight. Ponies and cobs with big crests, a fair covering of fat over their ribs, a very large fat pad in front of the udder or a gelding with a fat sheath are classic signs of being overweight. A weight tape can provide a useful guide to your horse's weight or alternatively talk to your vet if you think your horse may be overweight.
It is important to have the problem under control before spring as if you allow an overweight pony to graze the spring grass it will almost certainly get laminitis. Use strip grazing (section off part of the field with electric fencing) to control the daily intake of grass. A grazing muzzle only allows the animal to eat a small amount of grass and should be considered. Allowing cattle and sheep to pre-graze the pasture during the first flush of spring grass may be another useful aid.. Aim for pastures that have low nutrient grasses and don't forget there are flushes of grass growth throughout the year but particularly in April and May and often again in the autumn. The biggest mistake people make is thinking there is no grass in the field when in reality the pony is eating the new growth every day.
Laminitis should be treated as an emergency. The damage the disease causes can result in severe lameness and may ultimately result in euthanasia in some extreme cases. Call your vet immediately and remove the factors that have triggered the laminitic attack. Stable the horse on peat, sand, or shavings to provide a deep spongy bed to give the animal support for its soles. Depending on the severity of the laminitis your vet may apply frog supports to the feet and treat the patient with painkillers, anti-inflammatories and drugs which help to lower the blood pressure. If the animal has ingested a huge amount of grass or hard feed the vet may decide to stomach tube it with liquid paraffin and possibly Epsom salts to purge the bowel as quickly as possible.
A bad attack of laminitis can take many months to resolve especially if separation has occurred between the sensitive laminae and the hoof wall. In time the horse may need corrective shoeing or special shoes with frog support but your vet will advise you if this is the case.
Head Shaking
Head shaking is a distressing medical condition and not a vice or bad habit. It often affects horses in spring and early summer as this is when some of the more common factors that trigger the condition are present. At other times of the year a head shaker may appear to be perfectly normal.
It is an involuntary response and can vary from a slight twitch or tic, to violent shaking of the head in a typically up and down movement, or occasionally side to side. Symptoms are often only exhibited when the horse is ridden but some horses may display the problem at rest.
It is believed that the symptoms are in response to an irritation of the nerve that provides sensation to the face so the horse suffers anything from a mild tingling sensation to a severe electric shock. The condition has been likened to Trigeminal Neuralgia in people. It is thought that the nerve may become overly sensitive due to previous damage by a herpes virus. Nerve impulses can then be triggered by seemingly harmless things such as sunlight, breathing in pollen, faster airflow through the nasal passages, increased blood pressure etc.
Other conditions such as ear disease, sinus disease, gutteral pouch disease, eye disease or dental disease may also result in a horse shaking its head but are not likely to produce the classic head shaker symptoms.
Symptoms
The twitching movement of the head is an involuntary reflex response but the horse will then typically respond to the pain by rubbing its face on its forelegs and may actually strike at its own face in discomfort. It can be accompanied by a high or very low head carriage, sneezing or snorting, a watery nasal discharge and in some cases they may try to cover their nostrils to stop themselves inhaling the trigger. In severe cases the horse can become quite dangerous to ride.
Prevention and Treatment
It is sometimes possible to identify the trigger factor and thus avoid it, enabling the horse to be ridden without distress. For example, some horses are triggered by bright light, hedgerows or spring blossoms. Some continue to head shake in the winter whilst others stop altogether so it may not be possible to determine that a horse is a head shaker in the 'off season'.
Call the vet if you think you have a head shaker and he/she will investigate all the potential causes and determine whether your horse is a true headshaker or is suffering from one of the other conditions mentioned above. Unfortunately a true head shaker may be very difficult to treat as the symptoms are poorly controlled by any form of medication. If the trigger factor is an inhaled pollen or allergen the most useful treatment may be to fix a fine mesh over the horse's muzzle which prevents the allergens from being inhaled.
Recurrent Airway Obstruction (RAO)
Horses suffer quite commonly in the UK with an allergic airway disease that has traditionally been called chronic obstructive pulmonary disease (COPD) but is now referred to as recurrent airway obstruction (RAO).
Typically it is a winter condition but can affect stabled horses at any time of year when their environment is full of dust and allergens. When a susceptible horse breathes in the allergens often in the form of mould spore, it results in an allergic reaction in the lungs. This precipitates an increase in mucus production, a thickening of the walls of the small airways in the lungs and bronchial spasm (narrowing of the small airways). This results in coughing and laboured breathing being somewhat similar to asthma in humans.
All horses breathe out by relaxing the diaphragm and the muscles between the ribs so that air leaves the lungs passively. They will make a slight expiratory effort but in the normal horse this is not visible. In a horse with RAO you will notice a 'double lift' of the abdomen when he breathes out. This is because he needs to contract his abdominal muscles upwards to force the air out of the lungs through the narrow and congested small airways. You can see this in the horse's flank as a line in the abdominal muscles where they are contracted. This is known as the heave line hence the old name for this condition 'heaves'.
Symptoms
This condition typically results in coughing, increased respiratory rate and effort, a thick nasal discharge and reduced exercise tolerance. The horse will not be particularly sick but is unlikely to perform at his best. RAO can also strike susceptible horses as an acute attack, producing symptoms similar to those of an asthma attack in humans.
Prevention and Treatment
A healthy dust free environment is vital so you need to consider turning the horse out as much as possible, ideally 24 hours a day. If that is not possible then look at all forms of dust and allergen free feed and bedding. Haylage is preferable to hay but if you have to feed hay then ensure it is soaked long enough to become thoroughly wet.
Straw contains a lot of allergens so consider rubber floors with a sprinkling of paper or cardboard. Ammonia fumes are also an irritant to your horse's airway, so if you do use rubber matting you will need to keep it clean. Remember that the surrounding environment is also important so you will need to change the bedding for all the horses in the yard and not just those affected.
When the condition presents as a slight cough in an otherwise healthy horse, management changes and sometime oral medications prescribed by your vet are often sufficient to control the symptoms. In the event of an acute attack when wheezing and a greatly increase respiratory rate are evident, veterinary assistance will be required and the vet may administer corticosteroids or bronchodilators to enable the horse to breathe more easily.
Summer pasture associated obstructive pulmonary disease (SPAOD)
This can present itself as an acute attack of RAO but is often noticed in horses at pasture in spring or summer. Pollens and other environmental allergens trigger an asthmatic process resulting in similar clinical signs.
