Infectious pneumonia in foals and adult horses is usually a complication of stress or another primary disease process. Viral upper respiratory disease, strangles, colitis, and aspiration due to esophageal obstruction are common predisposing factors. Transporting horses over several hundred miles is associated with increased incidences of infectious pneumonia. This article consists of clinical signs, diagnosis, and treatment of pneumonia, pleuropneumonia, pleuritis in horses.

• pneumonia
  Inflammation of the tissues of the lung characterized by consolidation of the affected part, the alveolar air spaces being filled with exudate, inflammatory cells, and fibrin. Most cases are due to infection by bacteria or viruses, a few to inhalation of chemicals or trauma to the chest wall, and a small minority to rickettsiae, fungi, and yeasts. In horses, allergies to mold spores are a common cause of pneumonia with cough and no fever. Distribution may be lobar, segmental, or lobular; when lobular and in associated with bronchitis, it is termed bronchopneumonia.
• pleura
  The serous membrane enveloping the lungs and lining the walls of the pleural cavity.
• pleurisy and pleuritis
  Inflammation of the pleura. Pleuritis can either be dry of with remarkable effusion in the pleural space between the lungs and chest wall.
• pleuropneumonia
  Inflammation of the lungs and the pleura surrounding it. Frequently infection has primarily infected one organ and extended to the other.