What is Coughing in Horses?
Coughing is a common clinical sign observed with many different diseases in horses. It can be seen in any age or breed of horse. Coughing is the result of the respiratory system trying to remove debris from the trachea and upper airways.
Symptoms of Coughing in Horses
Coughing may occur at the beginning of exercise, which can be normal. Persistent coughing through exercise, or at rest, indicates more serious inflammation or infection. Some horses may cough during eating, or if they’re stalled consistently. You may see coughing after a long trailer ride, or after contact with new horses.
If your horse is coughing more often than a few times during exercise, exhibits any additional signs such as snotty nose, lethargy, or fever, placing your horse in quarantine and calling your veterinarian for a work-up is recommended.
Causes of Coughing in Horses
Some causes of coughing are contagious between horses, whereas others are due to inflammatory processes.
This can occur from bacterial or viral infections, or after aspiration during a choke episode. Rhodococcus is the number one cause of pneumonia in foals under six months old.
Influenza and other respiratory viruses
Similar to people, respiratory viruses in horses are usually highly contagious, and characterized by cough, fever, and nasal discharge. You may also see depression, decreased appetite, or edema (swelling) in the legs. Younger horses are more commonly infected, and outbreaks can occur easily where these animals congregate, like during races, shows, and sales. Horses may start to show signs in as little as 1-2 days after exposure. These horses also become at-risk for developing secondary concurrent bacterial infections.
Formerly known as Recurrent Airway Obstruction, heaves is a chronic condition similar to asthma in humans.
Inflammatory Airway Disease (IAD)
IAD is similar to heaves, but is commonly seen in younger horses and does not typically include increased respiratory effort/rate at rest. Hypersensitivity to an allergen like mold or dust causes an influx of inflammatory mediator cells and white blood cells to flood the lungs repeatedly, causing inflammation. If left untreated, IAD can progress to heaves in later years.
In foals, Ascarids can create lung damage. In adults, lung infestation is rare, but can occur primarily by transfer from infected donkeys. These worms can cause damage to the lungs and inflammation as the body reacts to the foreign visitors.
Congestive Heart Failure
Severe heart failure can lead to fluid backing up into the lungs.
How Veterinarians Diagnose Coughing in Horses
Your veterinarian will perform a thorough physical exam, including lung auscultation (listening through the stethoscope) to check for crackles and wheezes, which can be signs of inflammation or fluid present. They may also perform a “rebreathe” exam, which involves placing a bag over your horse’s nose for 30-45 seconds. When they remove the bag, this will make your horse take a few big breaths, which allows for better auscultation. Additionally, a CBC may be evaluated for the presence of increased white blood cells, which will be seen with infection. Other diagnostics might include:
Radiographs can be used to check for signs of inflammation in the lungs. This is much easier in foals due to their small size, but chronic bronchial inflammation can be seen in older horses, which is typically indicative of heaves.
Ultrasound can identify fluid on the lungs, areas of condensation, or abscesses present on the surface of the lungs.
PCR assays are specialized lab tests that can check for influenza and other common respiratory viruses from a nasal swab sample.
Endoscopy involves a scope with a small camera on the end can be passed through the nose and into the upper airways to look for inflammation, masses, or foreign bodies.
Transtracheal wash (TTW) is a test where a small hole will be made in the trachea, and a small tube will be passed into the into it to reach the lower trachea. Saline will be expelled, then retrieved. The sample will be evaluated to determine the bacteria causing pneumonia.
Bronchoalveolar lavage (BAL) involves a small tube that is passed down the nostril, trachea, and into the first branches of the lungs. Saline will be expelled, then retrieved. The sample will be evaluated to check for red blood cells, indicative of inflammation from IAD/heaves, or bacteria.
Treatment of Coughing in Horses
If your horse has a bacterial pneumonia, your veterinarian will start them on antibiotics. Supportive care should be administered as needed, which might include anti-inflammatories (Banamine) or antipyretics (Dipyrone) to help lower fevers, and IV fluids if your horse is dehydrated. Horses with severe pneumonia may benefit from nebulized bronchodilators, antibiotics, or steroids to help open the airways and increase penetration to the lungs. If there is fluid build-up in the lungs, chest tubes may need to be placed to facilitate drainage.
Viral-induced coughing is typically treated with supportive care as well, and antibiotics if a secondary bacterial infection occurs.
For heaves and IAD, treatment is aimed at reducing inflammation; this is primarily done with steroids (Dexamethasone, Prednisone), anti-inflammatories, bronchodilators (Ventipulmin), and environmental management.
For parasitic infections, appropriate deworming and potential steroids to minimize inflammation during the die-off process will be used.
Horses with congestive heart failure may be put on diuretics such as Lasix to help reduce the excess fluid sitting in the body. Other medications can be implemented to help decrease blood pressure.
Recovery and Management of Coughing in Horses
Recovery from an infectious respiratory disease may take up to several weeks to months, if severe. Exercise should be limited, and work introduced gradually once your vet gives the all-clear.
Horses that have an inflammatory process causing their cough, such as IAD or heaves, may require long-term management to stay in comfortable, rideable condition. Medications such as bronchodilators and maintenance steroids may be used in addition to changes in husbandry (housing/feeding) practices. Husbandry practices that are commonly recommended to reduce coughing include:
Wetting down hay to minimize dust intake
Reducing the time your horse stays in the stall (where there is low air flow)
Stalling your horse near a door or window to ensure good ventilation and fresh air
Using shavings that are not dusty, or water them down as needed
Water down the arena footing as needed to minimize dust
If not managed well, coughing will lead to exercise intolerance, increased risk for respiratory infections, and chronic, irreversible inflammation of the lungs.
Coughing in Horses FAQs
Why is my horse dry coughing?
Coughing is a respiratory mechanism to help rid the airway of debris, dust, and other irritants. Coughing a few times during warm-up before exercise is common, as the horse begins to exert more effort.
Can worms cause coughing in horses?
Yes. Larvae of the lungworm Dictyocaulus arnfieldi, typically harbored by donkeys or mules, can be ingested by horses. Once the larvae mature, the females will reside in the lungs and cause inflammation and irritation. This can be difficult to diagnose, since eggs won’t always show up on a fecal exam. Typically, coughing caused by worms will be determined through a history of living with mules/donkeys, and a lack of improvement of cough with antibiotics. Lungworm infestation can be treated with Ivermectin or Moxidectin.
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