Many Conditions Make a Horse Cough
As a horse owner, you would not hesitate to seek veterinary care if your horse shows signs of lameness, colic, choke, or other immediate dangers. But what do you do when your horse shows signs that are less clear-cut, such as a cough?
There are dozens of reasons why your horse could be coughing. A cough could be a mild irritation, or it could indicate an underlying condition that needs treatment. This article describes information that helps narrow down the possible diagnoses and explains the tools and tests used by veterinarians to figure out what is making your horse cough.
Check for Fever
The first thing to determine is whether your horse has a fever. Take your horse’s temperature once or twice a day for several days. If the temperature is higher than 101.5° F, contact your veterinarian. A cough with a fever may indicate an infection or tumor, and warrants veterinary care immediately.
If you rule out a fever, the next thing is to take notice of your horse’s environment, times that he coughs, and whether there are any other clinical signs. This information will give your veterinarian more insight into what is going on. Does your horse cough more in one season than the others? Does your horse cough when he is in his stall or outside in turnout? Does he cough when he is eating? During or after exercise? Does he have nasal discharge? If so, is it coming from one or both nostrils? Is the discharge clear? yellowish? bloody?
Diagnosing a Cough: Stethoscope
Your veterinarian will start with a thorough physical examination that will include listening to the heart and lungs with a stethoscope. If an arrhythmia (irregular heart sound) is detected, a cardiac ultrasound may be needed. When a heart condition prevents the blood from being adequately pumped forward, fluid can accumulate in the lungs, causing a cough.
If abnormal respiratory noises can be heard in the lungs of your horse, your veterinarian may recommend a transtracheal wash or broncheoalveolar lavage. These tests involve collecting a sample of fluid so that cells from that area can be analyzed. A transtracheal wash helps to identify infection, such as a bacterial or viral pneumonia, whereas a broncheoalveolar lavage is appropriate when an infection is less likely and a lung or airway problem is suspected.
Diagnosing a Cough: Ultrasound
Ultrasound is a great tool for gathering information about the lungs. Sometimes disease is present, but the condition is not yet advanced enough for abnormal lung sounds to be detected with a stethoscope. A thoracic ultrasound allows veterinarians to visualize the lungs and diagnosis a consolidation (deflated lung that is no longer able to participate in oxygen exchange), fluid in the lungs, or other problems. If there is fluid in the chest (pleural effusion), ultrasound helps determine the most accurate location for thoracocentesis (collection of lung fluid for analysis), which will in turn provide more information.
Diagnosing a Cough: Endoscopy
An endoscopy is another useful tool for evaluating a horse with a cough. An endoscopy sends a tiny camera into the trachea, upper airways, and guttural pouches so the veterinarian can see what is happening. Tracheal collapse and partial obstruction of the trachea by a foreign body or a mass can be visualized via endoscopy. Conditions of the upper airway that can cause a cough include anatomic defects that result in the airway not being appropriately protected from debris, such as dorsal displacement of the soft palate, rostral placement of the palatopharyngeal arch, arytenoepiglottic fold entrapment, and subepiglottic cysts. The guttural pouches can be inspected for conditions such as empyema (pus in the guttural pouches), chondroids (small masses formed by hardened pus), and fungal infection.
Diagnosing a Cough: Other Clinical Signs
More information about your horse’s cough will help your veterinarian narrow down the problem more quickly and with fewer tests. If nasal discharge is present with a cough, skull radiographs (X-rays) may be warranted. With an infected sinus, discharge may travel not only out the nose, but also down the throat, causing a cough.
If the cough occurs only during or after exercise, it is possible your horse has exercise-induced pulmonary hemorrhage. In these cases, the blood sometimes runs down the throat and causes a cough.
If the cough occurs only when your horse eats, conditions such as a cleft palate, dorsal displacement of the soft palate, and soft palate paresis should be ruled out.
RAO vs. IAD
Two common causes of cough that owners often confuse are Recurrent Airway Obstruction (RAO), better known as “heaves,” and Inflammatory Airway Disease (IAD).
RAO is a condition that generally affects older horses. These horses show increased respiratory effort at rest, exercise intolerance, and a cough. It is frequently caused by an allergy, most often mold or dust.
IAD is a condition that generally affects younger horses. Signs also include exercise intolerance and a cough, but IAD horses do not have increased respiratory effort at rest. IAD is also believed to have an allergic component.
Treatment for both of these conditions consists of medical therapy and environmental changes. Initially the horse must be treated medically with anti-inflammatory medications and bronchodilators to allow the horse to breathe more easily. To keep the condition from coming back, environmental changes—removing the irritants from the horse’s environment—must also be made. Examples include giving the horse a stall with a window or by the door to ensure good ventilation and fresh air; turning the horse out at times when the barn has debris in the air, such as when the stalls are being mucked or when the aisle is being swept; not keeping hay stored above the horse’s stall; using shavings that are not dusty; wetting the hay; and keeping arena footing well watered to minimize dust.
The Diagnosis Is in the Details
Owners are often frustrated by the many possible causes of their horse’s cough because there are so many tests their veterinarian may need to perform. By paying close attention to when and where the cough occurs and any additional clinical signs, you can help your veterinarian find the cause of the cough and the cure for your horse.
By Lori Madsen, DVM