Bacterial Pneumonia in the Horse
Dr. Melissa R. Mazan
Pneumonia refers to inflammation of the lungs. In horses, this is usually due to a bacterial infection, most commonly the streptococcal species. Rapid breathing (tachypnea)
Most horses get pneumonia by inhaling bacteria, which are often normal inhabitants of the upper airways. The lungs are usually able to clear the bacteria rapidly. However, if your horse has a depressed immune system, or has taken in an overwhelming dose of bacteria, then he may not be able to get rid of the bacteria, and pneumonia (lung infection) will develop.
There are many risk factors for bacterial pneumonia: those most important include a recent viral upper respiratory infection, moderate to severe exercise or overtraining, long-distance transport, overcrowded barns, and esophageal obstruction (choke).
What to Watch For
Difficulty breathing (dyspnea)
Nasal discharge that may be clear or may look like pus
Decreased exercise tolerance
Fetid nasal breath
Enlarged submandibular lymph nodes (they lie under your horse's jaw)
Cough, especially if productive – horses often look as though they are chewing or swallowing after a productive cough
Your veterinarian will first perform a thorough medical history and physical examination, including careful auscultation (listening with a stethoscope) and percussion (tapping on the chest wall).
Your veterinarian will usually take blood for a complete blood count to look for infection and chemistry profile to check that all the other body systems are working properly.
Your veterinarian may choose to do an ultrasound of the lungs. This can show whether there is consolidation in the lungs, or a build-up of fluid.
Frequently, your veterinarian will perform a transtracheal aspirate, to obtain a culture of the fluid in the lungs.
Your veterinarian may choose to look at the trachea (windpipe) and beginning of the bronchi (breathing tubes) with an endoscope.
Antibiotic therapy is necessary in order to treat pneumonia. Your veterinarian will probably start out with a broad-spectrum antibiotic that is likely to kill streptococcal species, and then will change antibiotics if the culture results warrant a change.
The length of treatment will vary with the severity of the pneumonia. It may range from 7 days to 4 weeks or longer.
Monitor your horse's rectal temperature once or twice a day. The horse's normal temperature ranges between around 99° F to 101° F. Also monitor your horse for any increase in coughing or nasal discharge. Note whether his appetite is good, and whether he looks bright and alert when you enter the barn.
Keep your horse in a temperate, well ventilated but draft-free environment. Avoid damp, poorly ventilated barns. Try to avoid dusty bedding, or moldy, dusty hay.
It is extremely important that you follow all instructions for antibiotic treatment. Your horse is likely to look and feel better long before the infection is completely cleared. If you stop antibiotic treatment too early, the infection will recur, and may be more difficult to cure the second time.
Give your horse plenty of time to recover if he has just undergone strenuous exercise – his immune system will be down. Whenever possible, don't tie your horse's head up when shipping, and avoid hay bags.
Have any horse with a cough or fever evaluated by your veterinarian; most horses will have a viral infection, but a few will go on to get pneumonia.