For the Health of It
Pleuropneumonia is the term applied to pneumonia when it extends from the main airways ( bronchopneumonia ) to the thin membrane on the surface of the lung ( the pleura ) and the surrounding thoracic cavity . Once a bacterial pneumonia reaches the pleura , horses respond by producing large volumes of proteinaceous fl uid . Pleuropneumonia is the most severe form of pneumonia and often requires long-term hospitalization and intensive care to resolve . Horses with pleuropneumonia often have endotoxemia , thus they can develop many complications , including laminitis and death .
Pleuropneumonia is most commonly associated with long-distance transportation ( shipping fever ), but it also develops following esophageal obstruction ( choke ) and secondary aspiration pneumonia . Stress is often considered a contributing cause of shipping fever because travel is known to weaken host immune responses against infection . However , the position of the horse ’ s head and the way they are fed during travel likely play a more important role . Normally , horses have their heads down for long periods of time , which allow them to easily clear debris from their trachea and lower airways . Horses that are transported with their heads tied in elevated positions have decreased ability to clear their airways . In addition to head position , hay is often placed in a bag directly in front of the horse ’ s
6 • Walking On
Equine Pleuropneumonia
Reprinted with permission from Volume 31 , Number 3 of Equine Disease Quarterly
nose , so they are constantly inhaling debris and bacteria that then settles in the lower airways and incites infl ammation and infection . Pleuropneumonia does not always develop immediately and can go unnoticed for days to weeks after the inciting event . Obvious clinical signs include cough , increased respiratory rate and effort and purulent ( pus-like ) nasal discharge coming from both nostrils that often has a fetid odor . Subtle signs include fever ( greater than 101.5 ° F ), weight loss , decreased appetite and malaise . It is important to note that horses with pleuropneumonia do not always develop nasal discharge or cough . Diagnosis of pleuropneumonia is confirmed via imaging of the lungs and sampling of the airways to identify bacterial infection . Ultrasound is the most frequently employed mode of imaging , as it is portable and can be easily performed in ambulatory practice . Ultrasound can identify and measure fl uid in the thoracic cavity , which is the hallmark of pleuropneumonia . Ultrasonography can only be used to image the surface
of the lung , so radiography may also be performed to assess the deeper lung tissue .
Once pleuropneumonia has been identified via ultrasound , pleural fl uid can be sampled for bacterial culture and microscopic evaluation . Bacterial culture and antimicrobial susceptibility testing ensure that horses will be treated with targeted antimicrobial therapy . In normal horses , the mediastinum ( the division between the right and left side of the thoracic cavity ) has small slits in it that allow movement of small amounts of fl uid from one side of the thorax to the other . In pleuropneumonia , large amounts of infl ammatory materi-