Nasal Discharge in Horses

Key Takeaways

Nasal discharge is an excretion of fluids from one or both nostrils. 

• Varies in intensity and severity in horses, from clear to discolored and from innocuous to life threatening

• The characteristics of the discharge, such as whether it’s mucous or watery, drips from one or both nostrils, or if it’s bloody, may suggest the underlying cause

• Most commonly the cause is environmental, with dust or hay irritating the nasal cavity; bacterial or viral infections are also commonly associated with nasal discharge

• It is important to take quarantine measures for horses that present signs of infectious disease

• Physical examination, skull X-rays, analysis of the discharge, and endoscopy to visualize the sinuses are standard tests to detect the underlying condition when nasal discharge warrants investigation

• Treatment and prognosis depend on the underlying condition

A Closer Look: What is Nasal Discharge in Horses?

The type of discharge varies depending on the underlying condition.

• White or watery: usually  an environmental cause or an allergy if there are no other symptoms

• Yellow: indicates a viral or bacterial infection like influenza

• Bright red and bloody: must be treated as an emergency as it could be a fungal infection of the guttural pouches

• Rust colored and bloody: indicates that the blood is not fresh, which could be a sign of hematoma

• Creamlike: usually indicates pus due to a bacterial infection of the guttural pouches. This may be a consequence of strangles.

• Foamy: often accompanied with discharge of food from the nostrils, this is a sign of choking and is an emergency

The presence of bilateral (both nostrils) or unilateral (one nostril) discharge also helps indicate location of the underlying cause in the body. 

• Bilateral usually indicates a problem with the lower airway such as asthma, strangles, or pneumonia.

• Unilateral usually indicates a condition related to the upper airway, head, and sinuses. Tooth abscesses and ethmoid hematoma present with unilateral discharge.

The odor coming from the discharge is another important indicator. Foul-smelling discharge is often a sign of infection

Possible Causes

As with nasal discharge in all mammals, the possible causes are widely varied in severity and origin. The most common causes are non-infectious. A runny nose may be caused by irritation due to inhaled dust or hay irritating the sinuses. Other possible causes include:

• Viral or bacterial infection, such as influenza, equine herpesvirus, strangles, or a dental disease (e.g. tooth root abscess)

• Exercise induced pulmonary hemorrhage (EIPH)

• Guttural pouch mycosis: A fungal infection can damage the large arteries bringing blood to the head. This is a most serious case and can lead to bleeding out in a matter of minutes

• Ethmoid hematoma: A benign mass of blood vessels that grows in the nasal cavity

• Choke (or esophageal obstruction): Food stuck in the esophagus that can also block the respiratory tract

• Tumors and cancer

• Injuries

Risk Factors

Many cases of nasal discharge in horses are not alarming. The color and consistency of the discharge indicate various conditions, from a common cold to a lethal infection. If the discharge presents as a bloody, bright red flow, it is a sign of emergency. 

If nasal discharge is accompanied by other symptoms such as fever, changes in appetite, or changes in other bodily functions, prompt veterinary attention is advised. Some conditions associated with nasal discharge are contagious, so quarantine is recommended for affected horses when the symptom first appears.

Testing and Diagnosis

Aside from the characteristics of the discharge and other possible associated symptoms, these tests may help with diagnosis of underlying cause:

• Nasal swab analysis under the microscope • Skull X-rays  • Ultrasound of the lungs • Blood tests • Physical examination

• Endoscopic visualization of the upper airways • Bronchoalveolar lavage to identify cells present in the airways

Treatment depends on the underlying condition.

Similar symptoms

Nasal discharge is unique and self-evident. It is not likely to be confused with any other symptoms.

Associated Symptoms

Other symptoms that may present alongside nasal discharge include:

• Fever • Decreased fecal production • Cough • Lethargy • Changes in eating or drinking habits

Exercise intolerance

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