Acute Broncointerstitial Pneumonia (Foals) in Horses

Acute bronchointerstitial pneumonia occurs irregularly and progresses swiftly in foals ranging in age from one week to eight months in age. Reported in North America, Australia, and Europe, the disease presents with sudden respiratory distress and the mortality rate is high. The factors leading to the illness have not been clarified and it is thought that the illness may develop as a result of various things as opposed to one particular factor. In acute bronchointerstitial pneumonia, the foal will experience significant damage to their lungs as well as sudden and significant respiratory difficulty. Acute bronchointerstitial pneumonia is also known as an acute lung injury and this can lead to ARDS or acute respiratory distress syndrome.

With an acute onset and swift progression, acute bronchointerstitial pneumonia in foals will present with sudden respiratory difficulty and fever.

Should your foal be suffering from acute bronchointerstitial pneumonia, he will appear to become ill suddenly and will show a high fever. Progression of the illness is quick and can lead to sudden death as a result of respiratory failure. Affected foals will either be unable or unwilling to move and they will not have the right amount of oxygen in their blood. The most obvious symptom of acute bronchointerstitial pneumonia is the significant respiratory distress.

• Fever
• Respiratory distress

Types 

Bronchointerstitial pneumonia may develop as a result of one of several different organisms; there is not one consistent organism that causes this condition. Bronchointerstitial pneumonia and R equi pneumonia present similarly upon examination.

Lung cultures of affected foals have shown organisms like Rhodococcus equi, Pseudomonas aeruginosa and Pneumocystis jiroveci though no single organism is recovered on a consistent basis. A good number of foals with the condition were undergoing antimicrobial therapy when they displayed symptoms. Residing in temperatures above 85% F is also common. The illness typically occurs as a secondary condition to a primary respiratory infection.

Should your foal have a fever and/or appear to be experiencing respiratory distress, you will want to contact your veterinarian, who will conduct a physical examination of your foal. Depending on the results of the physical examination, your veterinarian will choose how to best proceed. Arterial blood gas will be evaluated and will help the veterinarian determine how severe the foal’s respiratory problem is, as well as to monitor progress once the foal is receiving therapy. Other evaluations include:

• Complete blood count
• Serum chemistry analysis
• Thoracic radiographs

Should your foal be experiencing acute bronchointerstitial pneumonia, it is likely that he will show below normal levels of oxygen and high levels of carbon dioxide in his blood. It is also likely that your foal will be experiencing respiratory acidosis. As findings may be similar in nature to foals that are experiencing R equi pneumonia, the thoracic radiograph is a key test utilized to determine whether your foal is experiencing R equi or bronchointerstitial pneumonia and how advanced the disease is. In acute bronchointerstitial pneumonia, when fluid from the membrane around your foal’s lungs is tested, neutrophilic inflammation, possibly including sepsis, is found. In foals with bronchointerstitial pneumonia, Y neutrophilic leukocytosis is often seen.

The treatment for foals experiencing acute bronchointerstitial pneumonia will be for the symptoms that the animal is experiencing. This will likely include:

• Antibiotics that are effective against a wide-range of bacteria to treat secondary bacterial infections
• Medication to help with inflammation (for example corticosteroids like dexamethasone 0.1 mg/kg/day by IV); this is known to increase the foal’s possibility of surviving the illness
• Bronchodilation
• Oxygen
• Thermoregulatory control
• Alcohol bath
• Air-conditioning, a fan or both in the stall where the foal resides, as well as NSAIDs in order to keep a rectal temperatures of under 103.5 degrees F
• Clean environment
• Easy to eat feeds without dust

In acute bronchointerstitial pneumonia, the low level of oxygen in the blood of the foal can be resistant to supplemental oxygen therapy.

The mortality rate for foals with this condition is high, however should your foal promptly obtain aggressive treatment, he will have a positive prognosis. It is important to follow the recommendations of your veterinarian to allow your foal the best chance for recovery. Your veterinarian will conduct thoracic radiographs in order to determine if treatment is effective (radiographs will show improvement). Once your foal has recovered from acute bronchointerstitial pneumonia, the long-term impact on his lungs will vary. Some foals will show minimal to no symptoms of illness while others will experience ongoing trouble when they exercise.