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Atypical Myopathy

A myopathy is a condition affecting the muscles where damage to the muscle cells releases enzymes into the blood, causes significant pain and limits the horse’s ability to move. Typical myopathies are related to exercise such as ‘tying up’ or rhabdomyolysis as it is technically known and conditions such as PSSM. Atypical myopathy refers to a myopathy which is not related to exercise and appears to come from nowhere. It is caused by ingestion of sycamore leaves, seeds or seedlings which contain a toxin called hypoglycin A. It is therefore also known as sycamore poisoning. There appears to be variability in the susceptibility of individual horses and also in how badly affected horses are in different years and seasons. The disease is seen in autumn and winter when the sycamore seeds are on the ground and again in spring when the seedlings are growing, and young horses are most at risk although it can affect any age.

Symptoms

Horses may demonstrate one or more of the following symptoms:

• Weakness or walking oddly
• Low head carriage
• Muscle tremors
• Sweating
• Laboured breathing
• Looking like they have colic but they usually still have an appetite
• Dark coloured urine – brown or red
• Down and unable to stand

Diagnosis

Clinical examination will raise suspicion including recognising the above symptoms as well as the horse having an elevated heart rate but normal temperature and gut sounds usually so it can be a rather confusing clinical picture. A blood test will confirm a significant myopathy by elevations in blood enzymes called CK and AST. In severely affected horses the kidneys will be damaged too which will also show on the blood test. A confirmation of the disease can be achieved via a muscle biopsy being sent to a laboratory which can also be used to prove cause of death via a postmortem examination.

Treatment

1. Stopping any further ingestion of toxin by removing the horse from the pasture. Stomach tubing with activated charcoal may be used to reduce further absorption of toxins from sycamore in the horse’s digestive system.
2. Aggressive fluid therapy via a drip to support the kidneys, maintain hydration and flush the enzymes and toxins through the system.
3. Pain relief.
4. Vitamin E for muscle support and antioxidant properties.
5. Nursing – meeting the horse’s care needs such as support in feeding or comfort if recumbent.

Due to the intensity of care required in these cases referral to an equine hospital may be required.

Prognosis

Unfortunately, atypical myopathy carries a very poor prognosis, and it leads to death in 75% of affected horses. Poor prognostic indicators include kidney failure showing on the bloods, horses which are down and unable to stand and horses which are not clinically improving within the first few days of treatment. Due to the grave prognosis it is reasonable to consider early euthanasia in severely affected horses or  if financial and practical situations preclude an attempt at the intensive treatment required.

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Asthma

What is asthma?

Asthma is an inflammatory disease affecting the lungs which is triggered by environmental factors including dust and pollen. It was historically known as COPD and RAO and can also be referred to as heaves or broken wind. It is not contagious and often life long to a degree requiring ongoing management to prevent flares.

Symptoms

There is a scale of symptoms which correlates with severity of disease fairly well.

Mild disease:

• No signs at rest, only signs when exercised
• A cough or a few coughs at the start of a ride particularly when go into trot but then nothing more once gets going
• A slight runny nose after exercise – clear or white

Moderate disease:

• Some mild signs at rest, worse signs when ridden
• Snotty nose at rest, usually found on the floor over the stable door in the morning. The snot can be thick white or creamy coloured
• Coughing occasionally at rest particularly after eating, coughing more consistently when ridden not just at the start
• Some reduced athletic performance or exercise intolerance such as seeming to tire quicker, clearing nose more, breathing heavier or having flared nostrils at exercise
• Heave line seen during or after exercise. This refers to a visible line at the back of the abdomen between the tummy muscles and becomes obvious because the horse is having to use these muscles more to breathe

Severe disease:

• Marked signs at rest
• Coughing frequently at rest particularly after eating
• Snotty nose frequently at rest – seen on stable floor and at nostrils. The snot is creamy or white or may be yellow or green if a secondary infection is present
• Heave line at rest
• Visible increased laboured breathing and flared nostrils at rest
• May appear dull or not right and not want to eat like normal
• Acute asthma attack – panting, visibly struggling to breathe, noisy breathing

If a horse demonstrates signs of severe disease and you suspect they may be experiencing an acute asthma attach an emergency vet visit is required.

Diagnosis

Asthma can be diagnosed or at least suspected based on clinical assessment alone sometimes. Ruling out an infection may be required via a blood test or nasal swab. Accurate definitive diagnosis requires a tracheal wash or bronchioalveolar lavage test done via endoscopy under sedation. The samples taken during the endoscopy are sent to a laboratory for analysis of the cells and high levels of particular inflammatory cells (neutrophils) in the absence of infection determines asthma.

Treatment

Initial stabilisation and treatment of the episode:

Steroids

the underlying driver of asthma is inflammation and so treating this is key and often requires steroids. This may be a one-off injection, a course of oral tablets and/or inhaled medications via a nebuliser, aservo inhaler or human inhalers via spacer.

Buscopan

Most commonly associated with colic this drug is useful in the emergency asthma attack scenario as it relaxes smooth muscle – whereas in colic this is useful to stop stomach spasms, in asthma it reduces bronchial spasms and relieves symptoms quickly. This is a one-off injection.

Ventipulmin

An airway opener relieving bronchial spasms which can be given orally in food for up to 2 weeks as a course of treatment.

Sputulosin

This breaks down mucus making it easier to cough up and clear the airway and may be indicated if your horse is producing a lot of mucus. It is a powder which goes in feed for a course of treatment.

Remove any obvious triggers

See management measures

Preventing Recurrence

Controlling the environmental triggers

See management measures.

If environmental control is not sufficiently preventing symptoms (i.e. flare ups happen frequently) then a low dose of ongoing medication may be required. This is most commonly done now using a nebuliser to deliver steroids, saline or ventipulmin directly to the lungs. The alternative is pulse therapy with oral or inhaled steroids and/or ventipulmin when the symptoms are worse.

Management Measures

Horses suffering from asthma are usually triggered by one of two things – dust or pollen. Generally, these will then either be seen in the winter or summer. Of course, horses can be sensitive to both and there can be some cross over but it is worth monitoring timing of any patterns to help pinpoint the trigger.

Dust and mould

The biggest source of dust is straw, next is hay, then soaked hay, then steamed hay and haylage. The first thing to address with an asthmatic horse is the stable environment. Firstly, if possible, these horses may do better living out 24/7 – there is no better airflow than being outside. If stabling is required, then optimal airflow needs to be considered – this can be as simple as opening windows and doors or making some if they don’t exist. A deep clean and de-cobweb is required and switching to a dust free bedding will play a big role. A huge trigger is the forage they eat, dry hay is likely to be a problem for an asthmatic horse and if you watch a horse eat you will see the spores released from hay as they eat it and inhale it immediately. Likewise keeping feeds soaked can reduce the physical irritation at the back of the throat which may trigger a cough. Haylage or steamed hay is optimal, soaked hay may be sufficient for a less severely affected horse. Regardless of the type of forage the quality and cleanliness of it is imperative and no mouldy forage should be fed to an asthmatic horse.

Pollen

This is trickier to manage as pollen is everywhere and you can’t prevent it. All you can do is reduce exposure and manage symptoms meaning that summer affected horses tend to be harder to manage. It may help to stable the horse (in a well-managed dust free stable) during high pollen times of the day, there are apps which are useful at helping to see when the pollen count is high to help guide this. Sometimes it can be clear which pollens trigger a horse more, for example earlier in the season tends to be tree pollens and some are particularly affected when nearby rapeseed is harvested. Learning these triggers can help you prevent recurrence the following year by being prepared – e.g. move to a field away from many trees or stable during the harvest. Other simple things which may help include using Vaseline around the nostrils to capture pollen reducing inhaled amounts and using a pollen specific nose net. Exercise will always increase the risk of an asthma attack so if you know your horse is pollen sensitive it may be sensible not to ride during these periods or peak times of the day. In some cases, systemic anti-histamines are helpful such as piriton 4mg tablets, although the dose rates are high with an average 500kg horse usually needing around 20 tablets twice a day to see some effect and this will work better in a preventative way opposed to once symptoms have started.

An area of interest in these cases is immunotherapy

Which is essentially vaccinating the horse against the allergens that he/she is allergic to. The immunotherapy we use via injections for allergic skin diseases in horses is thought to not be effective against asthma although some people try it. In the last few years there has been research into inhaled immunotherapy which shows some promise in asthma cases (in humans and horses) so this may play a role in treating these horses in the future.

Prognosis

Mostly asthmatic horses can be well managed and live with a good quality of life. However, it can be labour intensive and expensive as it is a condition that the horse will have for the rest of its life, and it may worsen with age. It may also have an impact on the athletic use of a horse during periods of time where the horse’s trigger is bad and if the horse is rendered exercise intolerant they cannot perform in their intended way. In some scenarios despite the most committed management and best treatments horses can become too severely affected or unresponsive to treatment and require euthanasia sadly. Thankfully this is the minority of cases and a worst-case scenario with most horses doing well.

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Laminitis

Laminitis is a common painful condition affecting the feet of horses, ponies and donkeys. The name describes the disease process well – ‘itis’ meaning ‘inflammation of’ and ‘Lamini’ referring to the laminae. The laminae are a network of intertwining finger-like soft tissue structures inside the hooves which attach the internal and external hoof structures to each other. They are incredibly strong and vitally important. When they become inflamed they swell and tear which causes the internal hoof structures to become separated from the external structures – this manifests as the pedal bone rotating and dropping away from the hoof wall. This process is extremely painful and a significant welfare issue for the affected horses.

Causes

Firstly, it is important to note that any horse can get laminitis, not just a certain type. All horses have a threshold which if it is crossed, they can be triggered into a laminitic state. We see laminitis cases in slim thoroughbreds as well as good-doer ponies.

The largest proportion of laminitis cases are caused by underlying hormonal conditions. These conditions are equine metabolic syndrome (EMS) and cushings disease. For more details on these conditions see their own pages. These conditions cause laminitis because they lower the horse’s laminitis threshold so that factors that would not normally trigger a laminitis episode then does. For example, there can be 10 horses in a field all eating the same grass and then one of them will get laminitis. If it was just the grass causing the laminitis they would all have it but they don’t, there is some dysregulation going on within the affected horse meaning their threshold has been lowered and then they get it. A common real-life example of this would be with an EMS horse – the sugar in the grass is the trigger but a healthy metabolic system would deal with this threat and prevent disease, however in EMS the horse is resistant to the hormone insulin meaning that they cannot manage the sugar threat and end up with clinical disease.

A less common cause of laminitis is traumatic. This can be due to overloading due to a severe injury on the other limb, known as weight-bearing limb laminitis. This should always be considered if a horse is non-weight bearing lame on one limb for a prolonged period – the other foot should be supported by deep bedding or frog support and closely monitored. Traumatic laminitis can also be caused by poor foot balance causing unhealthy forces through the feet or over-working on hard ground.

Another type of laminitis seen rarely is toxin induced laminitis. This is a severe consequence of systemic sepsis from a nasty infection such as colitis or retained foetal membranes and is caused by the endotoxins and reduced blood supply to the feet.

Symptoms

The symptoms can vary and be on quite a spectrum depending on the severity of the episode and how many feet are affected. Laminitis can affect one single foot, all four feet or anything in between. Likewise, it can affect the just the front feet, or just the hind feet or all-round.

The classic laminitic appearance is a horse or pony unwilling to move, in a ‘rocked-back’ stance with the front feet out in front and weight through their heels, bounding digital pulses and hot feet. This is usually if both front feet are affected either in isolation or much worse than the hinds.

If all four feet are affected the horse may not rock back as they can’t overload the hinds because they also hurt. These horses are just unwilling to move, stiff all over from holding themselves, with bounding digital pulses in all four feet. If you can force them to move they are lame on every foot and look like they are walking on hot coals.

If only one foot is affected it will present as a severe lameness in one foot and initially be indistinguishable from a foot abscess or bruised foot.

In more subtle cases the horse may be able to walk well enough in a straight line but show soreness on turns or just look stiff – there is a spectrum and if caught in the early or milder stages then it may not be immediately apparent that it is laminitis. In severe cases the horse may lie down to take the weight off the feet.

Treatment

First aid from you in the first instance involves getting the horse into a stable if possible and starting box rest on a deep bed whilst waiting for a vet. If you cannot move the horse from the field, then leave them there and we can help when we arrive. If you don’t have access to a stable don’t worry, we can wrap the feet with supports or you can put mats and/or bedding in a small area in the field.

The aims of initial veterinary treatment are:

1. Relieve pain and anti-inflammatory treatment.
2. Prevent it getting any worse – stabilise the feet to prevent any further laminae separation.

Pain relief is given intravenously and then a course oral medication will be prescribed for at least a few weeks. The pain relief used also has anti-inflammatory effects to treat the inflammation and reduce further damage. A combination of a non-steroidal anti-inflammatory such as phenylbutazone alongside paracetamol is often used.

Providing support to the soles of the feet is essential and is achieved by application of upward pressure in a certain way to the sole to support the pedal bone against the weight of the pony whilst the laminae (i.e. their attachment) is inflamed and at risk of failing. This can be achieved with standing on a very deep shavings bed so the feet sink into it, application of frog supports or whole sole supports such as squish pads. During this acute phase of disease it is essential that the horse stands still. The laminae are injured and are at risk of tearing which will result in pedal bone rotation with too much movement so box rest really is essential. Another element of stopping it getting any worse is reducing any sugar and starch intake as these will trigger further laminae damage – in practical terms this means soaking the hay and ceasing and feed which contains sugar or starch.

The next phase of treatment involves:

1. Identifying and treating any underlying conditions.
2. Assessing the level of pedal bone rotation to make a shoeing plan.

Blood tests are indicated to screen for cushings and EMS and then starting treatment as soon as possible to reduce the driving force behind the laminitis.

X-Rays are indicated to visualise where the pedal bone is within the hoof capsule and to see if there has been any gas pocket or seroma formation which would require further treatment. From the x-rays the vet and farrier can formulate a plan to best support the recovery and correct any rotation or sinking. Advanced farriery techniques have transformed the ability to treat severe pedal bone rotation and sinking. Farriery required in treating laminitis will range from a therapeutic trim right through to clogs and casts. A good working relationship between the vet and the farrier is key in laminitis cases.

Regular reassessments will be required to assess when the horse can resume some walking exercise and turn out safely. The time frame for recovery is very individual and depends on so many factors and can range from a few weeks to a few months.

Prognosis

Most horses make a full recovery from a laminitis episode however it can be life-threatening in severe cases where there is too much separation of the laminae to be able to recover. If a horse has laminitis our aim is to prevent it ever happening again. However some horses become prone to recurrent episodes and if this cannot be controlled by treating and managing underlying conditions then the horses welfare should be considered.

Prevention

Maintaining a healthy body weight and exercise level for your horse is something simple which can prevent insulin dysregulation and therefore laminitis. Consider high fibre, low starch/sugar feeds for most horses, prevent over-rugging and monitor grass intake. Hay is just dry grass and can be up to 10% sugar content – soaking can reduce the sugar content dramatically and is a good trick for managing good-doer horses without having to ration the amount they eat. We know that feed intake is responsible for body fat levels and exercise is responsible for insulin regulation. In the wild horses walk many miles every day and eat very low quality forage – if ever we are unsure of how to manage our horses we should consider this. Also keep up with regular farriery to prevent foot imbalances and monitor hoof health.

If you have any suspicion that your horse may have EMS or cushings then a blood test can be taken at any time. It will inevitably be better to treat these conditions before they result in laminitis as another way to prevent this painful condition.