Aspiration Pneumonia in Horses: Causes, Symptoms, Treatment, and Prevention

Aspiration pneumonia is a serious respiratory condition in horses that occurs when food, water, saliva, or foreign material enters the lungs instead of passing down the oesophagus into the stomach. The inhaled material triggers inflammation and infection in the lung tissue, which can quickly become life-threatening if not treated promptly.

This condition is often a complication of other problems, such as choke, dysphagia (difficulty swallowing), or neurological disorders, but it can also occur during bottle-feeding of foals or following sedation. Early recognition and aggressive veterinary treatment are essential for recovery.

What Is Aspiration Pneumonia?

Aspiration pneumonia is defined as an infection and inflammation of the lungs caused by the inhalation of foreign material. When a horse accidentally breathes in feed, saliva, or other substances, bacteria are carried deep into the airways, leading to inflammation, tissue damage, and infection.

Unlike simple inhalation of dust or irritants, aspiration pneumonia introduces organic matter that acts as both a physical blockage and a breeding ground for bacteria. This results in a combination of mechanical injury, bacterial infection, and inflammatory response within the lungs.

Common Causes

Aspiration pneumonia in horses can develop for several reasons, but it most frequently occurs secondary to another disorder or event that interferes with normal swallowing or oesophageal function.

Choke

One of the most common causes. When food or saliva backs up due to an oesophageal obstruction, the horse may inhale feed particles and fluid into the lungs during attempts to swallow or breathe.

Dysphagia

Difficulty swallowing can result from nerve damage, trauma, inflammation, or muscle weakness. Horses with neurological diseases such as botulism, equine protozoal myeloencephalitis (EPM), or guttural pouch disorders are particularly at risk.

Iatrogenic Causes

Improper administration of oral medications, drenches, or feeding tubes can cause aspiration if the material accidentally enters the windpipe.

Foal Feeding Errors

Bottle-fed or nasogastric-tube–fed foals are at high risk if milk enters the trachea during feeding. Premature or weak foals with poor swallowing reflexes are especially vulnerable.

Sedation and Anaesthesia

Sedated or anaesthetised horses have reduced swallowing reflexes. If food or water is present in the mouth, it can easily be inhaled.

Megaesophagus or Oesophageal Dysfunction

Horses with conditions that affect the oesophagus, such as megaesophagus or strictures, are prone to regurgitation and subsequent aspiration.

Signs and Symptoms

The signs of aspiration pneumonia vary depending on the amount and type of material inhaled, as well as how much time has passed before infection develops. Some horses show immediate respiratory distress, while others develop symptoms gradually.

Early Signs

• Coughing or gagging, especially after eating or drinking
• Nasal discharge, often containing feed or saliva
• Increased respiratory rate or effort
• Depression or reduced appetite
• Fever or elevated temperature

Advanced or Severe Signs

• Rapid, laboured breathing
• Harsh lung sounds or crackling noises heard with a stethoscope
• Lethargy or weakness
• Blue or grey mucous membranes (indicating low oxygen levels)
• Persistent cough or frothy nasal discharge
• Signs of systemic infection such as sweating, trembling, or high fever

If left untreated, aspiration pneumonia can lead to sepsis, pleuritis (inflammation of the chest cavity), or death.

Diagnosis

Because the early symptoms can resemble other respiratory diseases, accurate diagnosis requires veterinary evaluation. Your veterinarian will perform a thorough examination and may use several diagnostic tools to confirm the condition and assess the extent of lung involvement.

1. Clinical Examination

Listening to the lungs with a stethoscope often reveals abnormal sounds such as crackles, wheezes, or areas of silence (indicating fluid or pus buildup).

2. Endoscopy

An endoscopic examination of the upper airway and trachea can help identify feed material or fluid that has been aspirated.

3. Radiography (X-rays)

Thoracic X-rays are one of the best ways to identify lung inflammation, abscesses, or fluid accumulation caused by aspiration.

4. Ultrasonography

Ultrasound of the chest can help detect pleural effusion (fluid around the lungs) and areas of lung consolidation.

5. Tracheal Wash or Bronchoalveolar Lavage (BAL)

Samples of fluid from the trachea or bronchi can be examined for bacteria, inflammatory cells, and feed particles to confirm aspiration and guide antibiotic selection.

6. Blood Tests

Bloodwork may show elevated white blood cell counts or markers of infection and inflammation.

Treatment

Aspiration pneumonia requires immediate veterinary care. The goals of treatment are to control infection, reduce inflammation, support breathing, and prevent further aspiration.

1. Antibiotic Therapy

Broad-spectrum antibiotics are the cornerstone of treatment and are often given intravenously at first. Once bacterial cultures identify the specific organisms, the medication may be adjusted for optimal effectiveness. Treatment usually continues for several weeks.

2. Anti-Inflammatory Medication

Non-steroidal anti-inflammatory drugs (NSAIDs) such as flunixin meglumine help reduce fever, pain, and inflammation in the lungs.

3. Fluid Therapy

Intravenous fluids may be necessary for horses that are dehydrated, especially if they cannot eat or drink comfortably.

4. Nebulisation and Airway Support

Nebulisers can deliver antibiotics or bronchodilators directly into the airways, helping to clear mucus and improve breathing. Some horses may benefit from oxygen therapy in severe cases.

5. Nutritional and Supportive Care

Horses with concurrent choke, megaesophagus, or swallowing difficulties should be fed carefully using soft, soaked feeds or via alternative feeding methods. Strict stall rest and a calm environment help minimise oxygen demand.

6. Managing Underlying Conditions

Addressing the original cause, such as choke, dental problems, or oesophageal dysfunction, is essential to prevent recurrence.

Complications

Even with treatment, aspiration pneumonia can result in complications, especially if diagnosis is delayed.

• Lung abscesses
• Pleuritis or pleuropneumonia
• Chronic respiratory damage
• Sepsis or systemic infection
• Recurring pneumonia due to residual scarring or impaired lung function

Prognosis

The prognosis depends on the amount of material aspirated, speed of diagnosis, and severity of infection. Horses treated promptly often recover fully, though recovery can take weeks to months. Severe or neglected cases carry a guarded prognosis due to the risk of irreversible lung damage or abscess formation.

Foals and older horses tend to have a poorer outlook because of weaker immune systems and increased susceptibility to complications.

Prevention

Preventing aspiration pneumonia primarily involves avoiding the conditions that cause aspiration in the first place. Owners can significantly reduce risk by adopting the following practices:

• Manage and treat choke immediately to prevent inhalation of feed material.
• Avoid feeding or watering sedated horses until they are fully alert.
• Ensure correct use of oral syringes, drenches, or nasogastric tubes.
• Feed horses with swallowing difficulties small, soft, and well-soaked meals.
• Maintain good dental health to promote proper chewing and swallowing.
• Bottle-feed foals slowly and in a natural nursing position to prevent milk inhalation.
• Monitor horses with oesophageal disorders closely for any respiratory signs.

When to Call the Vet

You should contact your veterinarian immediately if your horse:

• Develops nasal discharge containing feed or saliva
• Shows coughing or breathing difficulty after eating or a choke episode
• Has a persistent fever or lethargy
• Exhibits rapid or shallow breathing
• Displays signs of distress or collapse

Prompt veterinary attention dramatically improves recovery chances and helps prevent chronic lung damage.

Conclusion

Aspiration pneumonia in horses is a serious, potentially life-threatening condition caused by inhalation of foreign material into the lungs. It often arises as a complication of choke, swallowing disorders, or improper feeding techniques. Recognising the warning signs, such as nasal discharge, coughing, and fever, and seeking immediate veterinary care are crucial steps for a successful outcome.

With early intervention, careful management, and attention to underlying causes, many horses recover and return to normal activity. Preventative care, particularly proper feeding practices, dental maintenance, and safe handling during sedation, remains the most effective way to protect horses from this dangerous condition.