It is very common for horse owners to assume that a runny nose is likely just a “virus” and that a tincture of time and some professional neglect might be in order. This may well be the case in many instances but let me warn you about some red flags that should immediately get your attention. What if the discharge is from only one nostril? What if there is some intermittent or even continual blood flow from the nostril? What if the discharge has a foul odour? In these instances it is very likely that something more than just “a virus” is at work.
Most nasal discharge associated with respiratory infection will be from both nostrils (bilateral). The discharge will in many instances be clear to mucopurulent (snotty), is often accompanied by a cough, possibly a fever and often a history of exposure to other sick horses. Viral upper respiratory disease can progress to infections deeper in the lungs and can certainly predispose to secondary bacterial infections of both the upper respiratory tract and lung. Horses with bilateral nasal discharges that are depressed, have a deep or guarded cough and who are not improving within a few days should definitely be examined by your veterinarian.
My focus for this article is on the discharge from only one nostril (unilateral). Of particular concern is a unilateral discharge that has a foul or bloody component to it. As you all know the head of the horse in most instances contains a brain and in all instances a large set of teeth, tongue, eyes etc. What you may not know is that the head also contains large sinuses, one of which the roots of the last 3 upper cheek teeth protrude into. Horses also have a unique structure called a guttural pouch. This is an enlargement of what we call the eustachian tube running from inside the mouth to the inner ear. The horse also has a group of bones inside the nostril called the turbinate bones. All of these structures have an important role in filtering and regulating the flow, temperature and pressure of air and blood as they enter either the lung or brain. All of these structures can become infected, injured or invaded by tumor. All of these structures, when insulted can result in a unilateral nasal discharge.
If you have a foul unilateral nasal discharge do not delay having a veterinary examination. Treatment for this problem can be as simple as a course of antibiotics and it can be as difficult as any treatment process that we as veterinarians deal with. A very thorough examination of the oral and nasal cavity should be conducted. An examination of the molar teeth and an x-ray of the teeth and sinus may find evidence of a tooth root infection, a cracked tooth, a loose tooth, periodontal disease or other causes of infection gaining entry from the mouth into the sinus. Remember the nasal sinuses drain into the nostril, hence nasal discharge can result from infected sinuses. If you have an infected sinus the treatment will vary depending on the cause. In many cases an offending tooth may need to be extracted to fix the problem and the sinuses may need to be opened and flushed. The turbinate bones inside the nasal passage may become infected with bacteria or fungus. The guttural pouch is also very susceptible to both bacterial and fungal infections. The guttural pouch contains important nerves and blood vessels which when infected lead to a unilateral bloody nasal discharge and serious neurological signs. Erosion of the internal carotid artery by infection in the guttural pouch can lead to sudden death. Unilateral bloody nasal discharge needs to be investigated immediately. Another cause of unilateral nasal discharge is a tumor like abnormality called an Ethmoid Hematoma. This is basically an enlarging balloon like, blood filled mass which grows in the nasal passage. It is usually, in the advanced stages, easily diagnosed by “scoping” the affected nasal passage. In many instances radiographs are also used as part of the diagnostic evaluation. We are fortunate that we have relatively ready access to CT and MRI technologies at the veterinary school in Pullman Washington. These tools can often provide very definitive diagnostics for nasal discharges and can help us develop a proper treatment plan for the problem identified.
As I have tried to outline, problems associated with discharge from one nostril can be varied, complex and often expensive. Early diagnosis with surgical and/or medical intervention is extremely important in treating these sorts of disease problems. If your horse has a nasal discharge, pay attention. Is it uni or bilateral? Does it have a foul odour, is the discharge blood tinged? If it has any of theses characteristics then profession intervention and not neglect is in order.