Pneumonia in Horses

Some forms of pneumonia are more serious than others such as aspergillosis, which is fatal in close to 90% of cases and candidiasis, which is fatal in 45-70% of cases. There are a lot of different types and just as many different treatments, which include antibiotics, antifungals, antivirals, anti-inflammatory drugs, bronchodilators, and oxygen. With treatment, a healthy horse will almost always recover within a few weeks. However, older horses, foals, or horses with chronic illnesses may take longer to heal.

Pneumonia in horses is a lung infection that can be from bacteria, fungi, parasites, viruses, or aspiration (inhalation). Pneumonia can be a very serious disease in horses. In fact, it can even be fatal in some cases. The most common cause of pneumonia is streptococcus zooepidemicus, which is a form of bacteria. The signs of pneumonia are an increased body temperature, runny nose, cough, wheezing, and respiratory distress.

Since there are so many causes and types of pneumonia, the signs of infection can vary quite a bit. However, the most often reported include:

• High body temperature
• Nasal discharge (runny nose)
• Coughing (sometimes with blood)
• Raspy breathing
• Rapid or irregular breathing
• Shaking or shivering
• Sweaty skin
• Blue tint to mucous membranes
• Abdominal pain (colic)
• Facial deformities
• Weight loss

 Types

• Aspirational - breathing in dirt, hay, or other foreign substances
• Bacterial - bacteroides spp., bordetella bronchiseptica, clostridium spp., E. coli, klebsiella spp., pasteurella spp., pseudomonas spp., rhodococcus equi, streptococcus equi, and streptococcus zooepidemicus
• Fungal - aspergillus spp., candida spp., coccidioides immitis, cryptococcus neoformans, histoplasma capsulatum, mucor, phycomycetes, and rhizopus
• Parasites - parascaris equorum larvae and dictyocaulus arnfieldi
• Viral - equine influenza, herpesvirus, and arteritis

• Being around other ill animals
• Overcrowded living situations
• Horse racing or other high speed exercise
• Long distance travel

Your veterinarian (preferably one that specializes in horses) will need your horse’s medical history, vaccination records, recent illnesses or injuries, type of work performed, and what symptoms you have seen so far. A complete physical examination will need to be done, which should include palpation of the lungs and abdomen, listening to your horse’s lung sounds, and recording body temperature, weight, height, reflexes, capillary refill time (CRT), body condition score, personality, blood pressure, pulse, respiration rate, and conformation. You may need to trot, canter, and walk your horse while the veterinarian watches, analyzing behavior, muscle performance, and joint function while in motion. The veterinarian will start with a standing examination, checking your horse from head to tail looking for anything out of the ordinary such as swelling, warmth, redness, or lesions.

For any kind of pulmonary or respiratory illness in a horse, several thoracic radiographs (x-rays), ultrasounds, and CT scans are necessary. Collecting samples of fluid through a bronchoalveolar lavage or tracheal wash are also important in determining the cause. Microscopic examination of lesions taken from tissue and sputum from the lungs and airway can be extremely helpful. However, the most definitive tests are microbiologic culture, immunohistochemistry, or polymerase chain reaction. In addition, a complete blood count (CBC), chemical panel, blood and urine cultures, and blood urea nitrogen (BUN) will be done.

Treating your horse depends on the area and severity of the infection, the cause (agent) of infection, and the amount of finances available for treatment. Some of the treatments include oral, intravenous, or topical medications, hospitalization, fluid therapy, and oxygen therapy.

Medication

Antibiotics antivirals, antifungals, bronchodilators, nonsteroidal anti-Inflammatories (NSAIDS), and corticosteroids may be given, if needed.

Hospitalization

In many cases, your horse may need to be hospitalized for observation and further treatment as needed.

Oxygen and Fluid Therapy

Many horses need oxygen to help them breathe and intravenous (IV) fluid therapy to prevent dehydration.

Your horse’s prognosis depends on the type and cause of the pneumonia as well as your horse’s age and overall health. With aspergillosis or candidiasis, chances of recovery are low to moderate. All other types and causes of pneumonia can be treated successfully in many cases with treatment. Be sure to give your horse all of the medication even if the symptoms go away after the first few days. Not taking the full round of antibiotics can cause your horse to relapse.