E708
Respiratory Problems and Pneumonia

Introduction: Respiratory problems can occur in both young and adult horses. Most commonly, these problems are caused by infectious agents such as bacteria and viruses that infect and irritate the respiratory tract (lungs, trachea, and throat regions). Pneumonia (inflammation and consolidation) can result in many of these infections. Early diagnosis and proper treatment are critical in controlling these problems.

Causative Agents: Many cases of pneumonia are caused by bacteria, virus, and parasite infections. Below are some of the most common infectious causes of respiratory problems:

Bacteria Viruses Fungal Lung Worms
Streptococcus zooepidemicus

Pasteurella spp.

E. coli

Bacteroides spp.

Clostridium spp.

Klebsiella spp.

Pseudomonas spp.

Rhodococcus equi (foals)

Bordatella bronchiseptica

Streptococcus equi

 Influenza

Herpesvirus
(Rhinopneumonitis)

Equine Viral Arteritis

 Coccidioides immitis

Histoplasma capsulatum

Cryptococcus neoformans

Apergillus spp.

Phycomycetes

Mucor

Rhizopus

Candida spp.

 Dictyocaulus arnfieldi

Clinical Signs: The common clinical signs associated with a respiratory problem include a clear to yellow, runny to thick, nasal discharge. Coughing, and/or rapid breathing are often noticed. Harsh lung sounds when listened to with a stethoscope and a fever are also common. Enlarged lymph nodes can also occur, especially with a strangles or Streptococcus equi infection. Rhodococcus equi infections in foals can cause abscesses to be formed in the lungs.

Disease Transmission: Most of these infectious organisms are spread by direct contact with body fluids (nasal or eye discharge, saliva, etc.) or contaminated equipment, or when virus/bacterial particles are inhaled. Many of the bacteria are normally found in the upper respiratory tract. When the airways are damaged by a viral infection or other irritation, these bacteria invade the tissues causing an infection. Some of these infectious agents are brought to the respiratory tract through the blood stream. High levels of stress also increase an animal’s chances of becoming infected. Poor nutrition, intense training, extreme temperatures, poor ventilation, other diseases, and being transported all cause extra stress for the horse. Stress can lead to poor immune defenses and potential infection.

Diagnosis: The initial diagnosis can be made from general appearance and physical exam. Many horses will look and act sick with obvious signs of coughing and nasal discharge. There are often crackles, wheezes, and other harsh lung sounds noticed when listening to the lungs with a stethoscope. In foals and smaller horses, radiographs are often helpful to identify changes in the lungs. The information on page B890 can help identify the locations and areas to listen to with a stethoscope. Many of these horses also have a fever.

Blood work is also very helpful in identifying an infectious cause for the problem. An increased number of white blood cells (WBCs) often indicates a bacterial pneumonia. To accurately identify a bacterial cause of pneumonia, a transtracheal wash performed by a veterinarian, with culture and sensitivity is often necessary. An endoscopic exam may also be required to find the problem.

Treatment: The treatment for pneumonia depends on whether the cause is bacterial, viral, or parasitic.

  1. Bacterial causes: Treatment with antibiotics such as Naxcel or penicillin are often used in conjunction with products like gentamicin or trimethoprim and sulfadiazine. Like most bacterial infections, culture and sensitivity is recommended. See the antibiotic information in Section F. Anti-inflammatory agents such as Banamine and bute can also be given to relieve pain and inflammation.


  2. Viral causes: Treatment for all viruses involves treating the symptoms, not killing the virus. With this in mind, fluids, anti-inflammatory agents (Banamine or bute), and antibiotics for potential secondary bacterial infections are often recommended.

     
  3. Fungal causes: Most fungal infections are difficult and expensive to treat. However, if treatment is chosen, products like amphotericin B, ketaconazole, or miconazole are used.


  4. Lung worms: Dictyocaulus arnfieldi can be treated using ivermectin de-worming products on a regular basis.

Prevention: Prevention of viral and some bacterial pneumonia revolves around vaccination. For example, influenza, herpesvirus (rhinopneumonitis), and equine viral arteritis (EVA) can all be prevented with vaccination. See the vaccination schedule and recommendations on page A905 for additional details. Routine de-worming with ivermectin will help prevent lung worms. The fungal infections can sometimes be prevented by providing better ventilation, treating other diseases more quickly, and conservative use of steroids. Reducing the amount of stress placed on the horse can also help reduce the chance of all types of respiratory infection. If an animal has an infectious cause of pneumonia, it should be isolated from all other animals.

Other Causes of Respiratory Problems:

  1. Pleurisy or pleuropneumonia: Inflammation and pain that occurs in the lungs, along with fluid build-up (pleural effusion) around the lungs and in the chest cavity, is often called pleuropneumonia or pleurisy. It can be caused by bacterial, fungal, and viral infections. Stress, trauma, cancers, and equine infectious anemia can also cause this problem. In addition to the signs described previously under "clinical signs," these horses may have fluid (edema) accumulate under the chest, abdomen, and down the limbs. This problem can be diagnosed using ultrasound and thoracentesis (surgically puncturing the chest cavity to remove fluid). This problem is often treated with antibiotics and anti-inflammatory agents. In certain cases, draining the accumulated fluid in the chest is also required. Unfortunately, many horses that develop this problem never return to full activity.

     
  2. Pharyngitis (pharyngeal lymphoid hyperplasia): This is a problem where the tissues of the pharynx area (near the back of the throat) become inflamed. This is usually a result of bacterial or viral infections. Horses affected with this problem may experience nasal discharge, coughing, and have lymph node enlargement in the throat region. Diagnosing this problem involves observing the tonsillar tissues in the pharynx area. This tissue is often red, inflamed, thickened, and has yellow to white lymph nodules. Treating this problem can involve applying topical solutions, antibiotics, anti-inflammatory agents, and rest. Some mild cases may not require treatment at all. The best way to prevent this problem is to vaccinate for the common respiratory infections on a regular basis.

     
  3. Sinusitis: Sinusitis is defined as inflammation of the sinuses. This inflammation is most often caused by bacterial infections; however, fungi, neoplasia, and trauma can also cause sinusitis. Many of the bacterial infections enter the sinuses as a result of dental problems. The most common sign associated with this problem is nasal discharge. Radiography and endoscopy are the two most commonly used methods to diagnose this problem. Treatment for bacterial causes of sinusitis includes regular flushing of the sinus with antibiotic solutions through special portals placed into the sinus. If the sinusitis is caused by a tooth problem, the tooth should be removed.

     
  4. Exercise-induced pulmonary hemorrhage (EIPH): See page E222.

     
  5. Strangles infections (Streptococcus equi): See page E790.

     
  6. Chronic obstructive pulmonary disease (COPD): See page E305.

     
  7. Guttural pouch diseases: See page E295.
    8.

     
  8. Ethmoid hematomas: See page E219.