Aspiration Pneumonia in Horses

What Is Aspiration Pneumonia in Horses?

Just like in humans, horses have a larynx and pharynx “gateway” at the back of the throat that controls whether material goes down the esophagus into the stomach when we eat/drink, or down the trachea to the lungs when we breathe.

Aspiration pneumonia occurs when foreign material gets into the trachea and enters the lungs, carrying bacteria which then causes an infection. It can affect a horse of any age, although it is seen mostly in foals and geriatric patients. Aspiration pneumonia can lead to severe health problems, chronic breathing issues, and can prove to be fatal if not treated promptly.

Stages of Aspiration Pneumonia

Aspiration pneumonia is considered a medical emergency. If a horse experiences choke, broad spectrum antibiotics are typically administered by your veterinarian right away to help prevent aspiration pneumonia from occurring.

Acute

The acute stage is characterized by sudden onset of symptoms and can be life-threatening. An inflammatory reaction occurs in the lungs due to the foreign material. This can lead to marked respiratory distress and coughing.

Subacute

The subacute stage occurs when the acute stage of pneumonia has been left untreated for more than a few days. Cough and lethargy may worsen, and your horse may become lethargic and have a decreased appetite.

Chronic

If left untreated, bacteria settle into the favorable warm, moist environment of the lungs, and begin to proliferate (increase) unchecked. This can lead to severe inflammation and infection, pocketed abscesses, pleural pneumonia, toxemia, and other systemic effects as the bacteria travels through the body.

Symptoms of Aspiration Pneumonia in Horses

In the acute stage, the horse may exhibit signs of respiratory distress, such as rapid breathing, coughing, and nasal discharge. This can start within minutes of aspiration in certain cases. In severe cases in which large materials have been aspirated, the horse may collapse and be unable to rise. Early vague signs may include lethargy, decreased appetite, and a fever.

Symptoms of subacute and chronic phases include:

• Persistent cough

• Weight loss

• Difficulty breathing

• Lethargy

• Decreased appetite

Causes of Aspiration Pneumonia in Horses

The most common cause of aspiration pneumonia is the inhalation of feed, water, or saliva into the lungs during eating or drinking. This can occur if the horse bolts their food or eats too quickly, or if the horse has a problem with swallowing. Aspiration pneumonia is the number one complication of choke–when a horse gets food stuck in its esophagus. Large amounts of feed material or saliva work their way back up the esophagus, and either travel out the nose or down the trachea to the lungs.

Another common cause of aspiration is administration of liquids using a syringe or giving too much at once. Foals with a cleft palate or a poor suckle reflex are prone to aspiration as they experience dysphagia, or improper swallowing, when they suckle as newborns. Those who are bottle fed or syringe fed milk are also prone to aspiration due to an excess amount being given at once, or improper swallowing.

Other foals at risk include those involved in dystocias, meaning they were not facing the correct way during birth, and may have needed assistance making their way into the world by a veterinarian using either manipulation or a C-section. These foals are prone to meconium (fecal material formed during gestation) inhalation during the complicated birthing process. Fecal material in the lungs can lead to severe infection very early in life, which is difficult for foals to fight since they have a very weak immune system.

Other causes include viral or bacterial infections, which can weaken the immune system and make the horse more susceptible to infection. Horses that are kept in unsanitary conditions or exposed to dusty or moldy environments may also be more prone to developing aspiration pneumonia.

How Veterinarians Diagnose Aspiration Pneumonia in Horses

If a horse has recently choked, veterinarians often treat pre-emptively with antibiotics to prevent signs of pneumonia, unless the case was very mild and self-resolved quickly. If your horse is experiencing any of the above signs, diagnosis of aspiration pneumonia can be made with the following:

• Physical exam to listen to the lungs and run diagnostics such as bloodwork to check severity of systemic infection.

• Ultrasound or radiographic examination to determine the extent of lung damage. Ultrasound waves can only penetrate so deep, but are helpful to check for lung thickening, or abscess formation along the edge of the lungs, while radiographs can help evaluate consolidation or scarring.

• Transtracheal wash (TTW) may be performed to determine the exact bacteria causing infection. This involves placing a small hole on the outside of the throat into the trachea, then sterilely injecting saline into the lungs. The sample will then be retrieved via suction from a syringe, spun down for concentration, and sent to the laboratory for culture and sensitivity to determine the best antibiotic to use in treatment.

Treatment of Aspiration Pneumonia in Horses

If your horse is exhibiting any signs of possible aspiration pneumonia, it is important to have them examined by a veterinarian right away for diagnosis and aggressive treatment to prevent long-term complications. Depending on the clinical signs, treatment may include anything from medications administered at home, to hospitalization for intensive care and monitoring. Some common treatments your veterinarian may employ may include:

• Antibiotics

• Anti-inflammatories (Banamine)

• Oxygen supplementation

• IV fluids

• Feeding via nasogastric tube if anorexic

• Chest tube for drainage if there is fluid buildup in the lungs

Recovery and Management of Aspiration Pneumonia in Horses

Aspiration pneumonia is a common disease in horses, particularly in the young and senior populations. Depending on the severity of pneumonia, and how soon treatment is started, recovery may take anywhere from several days to several weeks; this is typically a gradual process, and the horse may or may not have lingering respiratory deficits. During the course of aspiration pneumonia, potential secondary complications include:

• Toxemia (bacteria entering the bloodstream, which causes systemic infection)

• Lung abscesses

• Pleural pneumonia

• Scarring of the lungs

• Increased susceptibility to respiratory infections

• Permanently decreased respiratory function

Preventing aspiration pneumonia involves taking steps to reduce the risk of inhaling foreign material into the lungs. This includes feeding horses in a calm, controlled environment and providing adequate water sources; horses who have repeat choke episodes may need a diet or feeding routine change.

Horses that bolt their food may benefit from “slow feeding,” or putting a few larger rocks in the feed bucket that they have to work around in order to get their grain. Senior horses or those with dental problems should have their teeth checked regularly by your veterinarian, who might recommend soaking their feed to allow for easier swallowing and decrease the chances of choke.