Humans need not fear that they’re the only species on the planet to suffer from asthma.
Horses can be similarly afflicted – it’s just that their asthma-like conditions just go under some different names.
Heaves, Broken Wind, and Chronic Obstructive Pulmonary Disease are all names for a respiratory disease that affects horses.
Like asthma in people, it can manifest itself in various ways, but the signs a horse will be showing all result from the basic problem: a narrowing of the lung’s small airways which can be caused by inflammation, tightening of surrounding muscles through spasms, or thickening of tissue.
This leads to a discharge and, potentially, a dangerous build-up of fluid in the lungs, which only serves to make breathing even harder.
The outward signs of heaves include trouble breathing, a decline in the ability of the animal to exercise, and possibly a cough. Those who listen with a stethoscope may well hear wheezing.
Horses will often look tucked up, caused by the extra effort they have to make in breathing. A line of abdominal muscles, called the “heave line”, may well be visible.
It is very likely the horse will have an accelerated breathing rate, and you are likely to notice the animal forcing its breath out.
In fact, the way in which a horse breathes can be an important indicator of heaves being the culprit. The exhalation will start quickly, but the flow of air will quickly fall away in each breath.
A horse with heaves may have a respiration rate of up to 36 or 40 a minute – well above the usual six to 12.
Some horses will have a nasal discharge, and it is unlikely the horse will be running a temperature.
Horses under six years of age are rarely affected.
Scientists don’t have a definite answer about the cause, but they do know that heaves has been affecting horses over many hundreds of years. Most evidence points to it being some kind of allergic response to mould and dust. Dusty hay is usually considered the biggest culprit – horse owners established this link more than 400 years ago.
It is a bigger problem in countries where horses spend a lot more time in stables, particularly those that are poorly ventilated and dusty.
Being linked to allergies, there is likely to be a hereditary element to the disease. Ponies seem more affected but it has been suggested this may relate to them being good “doers” who are sometimes feed poorer quality hay to help keep weight off them.
Heaves may also be triggered by a lung infection, but this, as well as other possible factors, is still the subject of research.
The good news is that horses will generally improve once the cause of the heaves is removed. This may involve removing the animal from a dusty stable or substituting a better quality and less dusty hay.
If hay is the likely culprit, owners are wise to thoroughly wet any hay before feeding it to the horse to eliminate the dust problem. An owner may choose to gradually switch their horse to a pelletised feed – ensuring that the horse still gets its daily requirement of roughage in its diet.
The horse should begin to show improvement and be back to normal from one to three weeks later, depending upon the severity of the case.
The bad news is that studies show a horse can start developing lung problems again as little as 90 minutes after being exposed again to dusty hay – or whatever the trigger factor proved to be.
If not dealt with, the lung linings will inflame, mucous will be produced and the smooth lung tissue will spasm. The lung’s tiny airways will not be able to carry as much air and the horse’s breathing will become laboured.It may take longer for the outward signs to appear to the horse owner, but an attack from even brief exposure can last for days.
Left untreated, heaves will not only be distressing for the horse, but can also result in permanent lung damage.
A vet who attends to a horse with suspected heaves will note whether the horse appears tucked up, with the heave lines visible. They will investigate the nature and rate of the horse’s breathing, and may well have the horse breathe for a minute or so into a bag, to increase its breathing rate. This will make abnormal lung noises more obvious through the stethoscope. He or she will take the horse’s temperature – an elevated temperature pointing to infection as being the more likely cause.
A vet is likely to take a blood test to eliminate a serious lung infection as the cause. A sample of fluid from the upper trachea may also be taken for testing, provided the vet has the specialized piece of equipment needed to take it.
Expect a thorough examination and testing, as a vet will want to eliminate other possible causes of the breathing difficulty, which can include various forms of pneumonia, lung-worm infection, some cancers, and even a hernia of the diaphragm. A blood test will be key in eliminating some of these conditions as possible causes.
In bad cases, a horse will be clearly distressed – its nostrils will be flared and its ribs may even be visible because of the extra effort needed to breathe. The animal will start to lose condition quite quickly.
What does the future hold for a horse that is prone to heaves? Some horses will stay well provided they are managed carefully and kept away from known triggers.
Owners used to stabling their horses for the winter may consider turning them out for the colder months, instead. A horse turned out in good condition with a quality coverwill generally do fine in the open, provided it is well fed. Use paddocks with good shelter from prevailing cold winds.
If this isn’t an option, the owner must ensure the stable is well ventilated, and may well have to switch to a low-dust bedding in all the loose boxes. Shredded paper or low-dust wood shavings are popular choices.
Any hay must be thoroughly wetted down before feeding.
Some horses will need ongoing medication to manage their condition, or at least while they recover from a bout of the disease.
Most of the drugs and strategies used in the treatment of asthma in humans apply to horses, with the use of corticosteroids and bronchodilators.
In some parts of the world, devices to deliver inhalants have been developed for horses – an alternative to delivering the medication by mouth or injection.
The solution to heaves sounds just like the formula for a healthy human. Plenty of fresh air and good quality feed.
The condition is far less common in New Zealand and Australia than in many nations because of the general preference to keep horses in paddocks rather than stables.
Originally published on horsetalk.co.nz in June, 2007