Spring 2011

SPRING EQUINE NEWSLETTER 2011

Spring will soon be approaching us, thankfully, after a long and very snowy winter! Horse owners will be looking forward to no more frozen water buckets, dark mornings and nights, and being able to turn their ponies out onto proper grazing and not just mud, snow, or ice in the field! Two serious equine diseases which we tend to see an increase of in the spring are Laminitis and Equine Grass Sickness. It is very important to be aware of these and to take what steps you can as an owner to prevent your horse or pony suffering from them.

Laminitis is one of the most painful conditions in the horse and it can be caused by many factors. All breeds can be affected by it, but we most commonly associate it with native “good-doers” who have been allowed excessive carbohydrate intake, usually through grazing rich, grassy pastures, or being fed too much hard feed or hay. Other causes can be generalised obesity due to hormonal conditions such as Equine Metabolic Syndrome/Type 11 Diabetes Mellitus or Cushings Disease. Overloading on the feet, either from excessive intensive work on hard surfaces or even from overcompensation for an injured limb, can also bring on Laminitis. Less commonly, other illnesses such as retained cleansing post foaling or even colic, lead to a condition called Endotoxaemia which can result in your horse rapidly developing acute laminitis.

The most commonly noticed stage is the acute phase where the animal has a sudden onset of severe pain and is very reluctant to move. There is a typical laminitic stance whereby the horse rocks back onto its heels, weight may be shifted from one foot to another, heat may be felt in the feet especially at the coronary band and a large pulse may be evident above the heels. The horse is happier walking on soft ground, finding hard concrete etc much more painful and concussive. Turning a tight corner is also awkward. They may lie down and be difficult to move, have a high heart rate, sweat and be generally distresssed. Milder cases may show a more gradual onset of stiffness leading to lameness, and the horse moves as though it is “walking over hot coals”. The fore feet are most commonly affected but it is not unusual to see all 4 involved. If you find your horse like this, please contact your vet immediately.

Several steps can be taken to avoid your pony succumbing to grass induced/excessive carbohydrate laminitis in the Spring. Try and make sure he does not put on too much weight over the winter, when he is at his most inactive, as it can be hard to lose when the young grass comes through. Regular exercise is more important than anything as this will stimulate his metabolism to burn off fat reserves and keep his weight constant. Restrict his grazing if your paddock is very large or you have an abundance of grass, either by strip grazing the field or stabling him for part of the day. Be sensible with the amount of hard feed you give him – this should only be necessary if he has a high workload and your grass quality is poor.

If you suspect he is developing laminitis, it is best to remove him from his field and stable him if possible, on a deep cushioned bed preferably of shavings. This will be far more comfortable for him to stand on and will help to cushion his sore feet, and it may also encourage him to lie down. It is best to feed him older hay which is not new season as this will have a lower sugar content. If he has to receive medications to ease his pain, mix them in with chaff based products which are suitable for laminitics. And if he is a little bit chubby, now is the time to try and lose some weight. Once he is feeling better, it may be worth contacting your farrier to assess his feet. Corrective hoof trimming and remedial farriery can make a huge difference to laminitics.

In cases which are unresponsive to box rest, anti-inflammatory medications, and remedial farriery, we would advise having x-rays taken of the affected feet to assess any changes to the pedal bone which sits within the hoof capsule. We would also recommend testing your horse for diseases such as Equine Cushings and Metabolic Syndrome(diabetes) at this stage.

Grass Sickness is a disease of horses, ponies and donkeys in which there is damage to parts of the gastrointestinal nervous system causing gut paralysis and often colic. Unfortunately it is often fatal but it should be remembered that it is much less common than other forms of colic from which it must be distinguished. The disease occurs almost exclusively in horses with access to grass and it has been recognised for over 100 years. Great Britain has the highest incidence of grass sickness in the world and it occurs in most areas of Scotland, England and Wales, especially more eastern regions. It also occurs to a lesser extent in Northern Europe, and Southern America and the Falkland Islands.

The cause is still unknown even though many potential causes, such as plants, chemicals, fungi, viruses, insects and metabolic upsets have been examined over the years. A common suggestion is that vitamin and mineral deficiencies may be the cause but none have any proven link although selenium deficiency, which results in reduced levels of protective antioxidants in the body, may have some role to play. Grass sickness does not appear to be contagious and the type of damage to the nervous system suggests that a toxic substance is involved. A major line of investigation at present is the role of the sole borne bacterium, Clostridium Botulinum type C in the disease. It has been discovered that the concentration of C Botulinum type C toxin is high in the intestine of acute cases and that horses with low levels of antibody to the bacteria and its toxin are at increased risk from the disease.

It occurs at all ages from young foals to over 20 years but most commonly at 2-7 yrs with a peak at 3-4 yrs. Young foals are very rarely affected and the lower incidence in older horses suggests that animals exposed to the causal agent develop a degree of resistance. Most cases have been at grass full-time or during the day, with certain fields being “bad” for EGS. Animals that have been on affected properties for less than 2 months are more likely to develop the disease . Usually only 1 horse is affected at a time but outbreaks can occur. There is no clear association with type of pasture (permanent pasture, hill grazing, clean or “horse-sick” pasture) but high Nitrogen content of soil and soil disturbance may be risk factors. Certain methods of mechanical droppings removal can disturb the soil more and possibly spread causal factors or agents over the pasture.

Stress also seems to be a factor with recent purchase and mixing with strange horses. Animals in good to fat condition are also predisposed. Most cases are seen in April/May with another peak in September/October in some years. Adverse or extreme weather changes causing a check or flush in grass growth rates, the majority of which occur in spring and autumn when late or early frosts and sudden weather changes are most likely, cause rapid and signifcant changes in the mineral, fructan and carbohydrate content of the grass.

EGS occurs in 3 main forms, acute, subacute and chronic but there is considerable overlap in the symptoms seen in the 3 forms. The major symptoms relate to partial or complete paralysis of the digestive tract from the oesophagus (gullet) downwards.

In acute EGS the symptoms appear suddenly. Severe gut paralysis leads to colic, rolling, pawing the ground, looking at the flanks, difficulty in swallowing and drooling of saliva. The horse is in extreme pain which is usually unresponsive to pain killing medication administered by your vet. The stomach may become grossly distended with foul smelling liquid that may start to pour down the nose. Further down the gut constipation occurs. If dung is passed, if at all, it is small hard pellets with a coating of mucus. Fine muscle tremours and patchy sweating may occur and the eyelids droop. This form is fatal and the horse should be put to sleep once a diagnosis has been made.

In subacute EGS, the horse shows less severe signs than the acute form and may still be able to eat, but they gradually deteriorate and generally need to be euthanased with a week.

In chronic EGS, the symptoms come in more slowly and some cases only show mild intermittent colic and can still eat small amounts. There will be varying degrees of difficulty swallowing but salivation, accumulation of fluid in the stomach and severe constipation are not a feature. One of the major symptoms is rapid weight loss that may lead to emaciation. Treatment can be attempted with these horses if they are not in too much pain and still show an interest in life. Not all chronic cases will respond so it is essential to choose these cases for treatment carefully. This involves the provision of palatable, easily swallowed food e.g. chopped veg and grass, and high energy concentrates soaked in molasses, which are essential. Intensive nursing is also vital, such as regular grooming to prevent them becoming sticky with sweat. Some may need intravenous fluids if they are unable to drink enough water and painkilling medication to make them more comfortable. About 50% of the milder chronic cases may recover and be able to return to work and be ridden. The others are often only able to be retired and have field rest but can still have a good quality of life.

Until a true cause is known, it is difficult to give sound advice regarding prevention, other than trying to avoid the risk factors previously discussed. The Equine Grass Sickness Fund is an organisation dedicated to supporting and advancing research into grass sickness and further improving the treatment of it. Visit their excellent website which can be found on our “Links” page for information on current research, advice and much more.

STRANGLES

A new improved Strangles vaccine is due to be launched shortly. Please contact the surgery in Kirriemuir for more information.