The sight of blood dripping from a horse’s nose can cause panic. But nosebleeds are a common problem and not necessarily something to worry about. Very occasionally, however, a nosebleed can be an early sign of something more sinister. While a minor, one-off bleed from one nostril may not warrant calling a vet, anything persistent or more frequent definitely requires investigation by a vet.
A common cause of nosebleeds is trauma, such as a bang to the head or from the passage of a stomach tube up one of the nostrils. Typically, a moderate amount of blood will be coming out of one nostril and the flow will stop of its own accord within an hour or so.
Other causes of bleeding from one nostril include nasal masses. These can range from small polyps to large tumours and tend to cause intermittent and moderate bleeds. The amount of blood will be less in the cause of an ethmoid haematoma, but these small bleeds may recur frequently over a long period of time.
Frequent bleeding from either one of the nostrils, or both, could point to a more serious underlying illness, such as thrombocytopaenia – a low level of platelets, which help the blood to clot. The amount of blood will be variably, with no particular pattern to occurrence or length of bleed.
Another possibility is exercise-induced pulmonary haemorrhage (EIPH). This can produce a variable amount of blood, usually out of both nostrils, after a significant period of exercise. The most useful diagnostic aid in investigating the cause of a nosebleed is endoscopy, which allows us to see where the blood is coming from. Video endoscopy, in which the image is seen on a screen, rather than down the more basic fibre optic scope, can often be done at a yard or clinic. Recent advantages in diagnostic imaging mean that we can now glean a huge amount of information from a CT scan, although this would be reserved for less obvious cases.
A nosebleed rarely requires immediate veterinary action, but one emergency scenario is an arterial bleed. If an artery has ruptured, blood will not be trickling from the horse’s nostrils – it will be pumped out at an alarming rate. A blood loss of more than 30% can be fatal. For a 500kg horse, this would equate to about 15litres, or a full water bucket.
Up to this volume, most horses can cope with a relatively large loss of blood. Blood will be diverted to essential organs, the heart rate will increase and the horse will also have the urge to drink substantial amounts of water to compensate. An arterial haemorrhage can occur if the horse falls over backwards and hits his head. This can tear or detach the longus capitus muscles attached to the base of the skull, fracturing the basisphenoid bone. A more common cause of this type of bleed, however, is guttural pouch mycosis (GPM).
GPM is a fungal infection in the guttural pouches – air chambers situated in the neck just behind the skull 0 that are unique to the horse and whose function is not fully understood. In GPM, the fungus frequently grows on the wall of the internal carotid artery at the back of the guttural pouch. As it develops it eats into, and then right through, the artery wall. It’s important that owners are aware of GPM and that any substantial nosebleed is investigated promptly. What starts out as a relatively harmless –looking bleed can be an early indicator that a massive and potentially fatal haemorrhage is about to occur. Left untreated, the horse can bleed to death.
Immediate action is crucial
Endoscopy of the guttural pouches is usually adequate to diagnose GPM. Once diagnosed, the horse should be taken immediately to a specialist equine surgical facility for treatment.
There are a number of ways to prevent the bleeding. The most straightforward is to ligate or tie the internal carotoid artery. The anatomy of the circulation in the region of the guttural pouch, however, is very complex and occasionally bleeding can continue, despite ligation.
More complicated techniques include transarterial coil embolization, where a small coil is inserted into the artery to encourage the blood to clot, and balloon catheter embolization, where the same effect is achieved using a tiny expandable balloon. Both techniques require fluoroscopy – or real-time X-ray imaging – and the use of highly specialised equipment available at only a few specialist centres.
Time is very limited with GPM. The emergency of these cases means that ligation of the artery is usually the most effective and practical treatment. Ligating the blood supply causes the fungus to die – a process that is not guaranteed, yet seems to happen most of the time. We also treat it topically with antifungals administered via a catheter into the guttural pouches.
Treatment and check-ups may be on-going for some months. While prognosis is guarded, most successful surgery results in the horse making a full recovery. GPM may be dramatic and potentially fatal, but thankfully it is not common. It is not infectious to other horses and there are no known reasons why one horse contracts it and another doesn’t. The fungus is present everywhere. As far as we know, there is nothing that can be done to reduce the chances of a horse developing the condition.
Owners can, however, be vigilant to the treat by seeking immediate veterinary attention in the case of a substantial nosebleed. Early action could be a lifesaver.