Respiratory Disease in a Horse

A 12 year-old mare presented for a history of increased respiratory rate and effort during the late summer months. In addition, a white discharge was noted from both nares. At presentation the mare had labored breathing, significantly nasal flaring and there was a large abdominal component to her respiratory effort (see videos below). Auscultation of the lungs noted wheezes and crackles and a very mild cough was elicited when the larynx was palpated. The client was of limited financial means and asked that I perform the fewest tests necessary to determine the source of the problem! As such, we opted to begin with an upper airway endoscopy to determine if there was any abnormality within the larynx and if not take a look down the upper trachea. The larynx was normal however there was a significant amount of white debris within the upper trachea (Figures 1-2). This white debris is otherwise known as sputum and is produced within the lungs by inflammatory cells!

Figure 1

Figure 2

The sputum present within the trachea may be due to an allergic airway condition known as heaves/COPD or it may be due to broncho-pneumonia!  These conditions present with similar symptoms but are treated quite differently. Hence making the correct diagnosis is essential! There are several diagnostic tests which will evaluate the lungs and the fluid within the lungs however the one exam that will give you all the information necessary to determine the cause of the sputum and how to treat is a trans-tracheal wash.  The trans-tracheal wash is performed by catheterizing the trachea through a small incision that is made along the ventral aspect of the neck, approximately half way between the horse's throat latch and thoracic inlet. The catheter is passed into the trachea and down to the level of the lungs. A small volume of sterile saline is flushed into the lungs and then aspirated out for analysis. This sample of fluid should contain the sputum noted in the endoscopy exam. The sputum is analyzed for cell type and for the presence of bacteria. If bacteria are found then the sample is tested for which antibiotic is most ideal to treat the pneumonia. This procedure is easily performed in the field with mild sedation and proper technique!

In this case, the mare was noted to be suffering from heaves AND pneumonia. This is not common but does occur and requires very specific medication to save the horse's life!! The horse was treated with a combination of systemic corticosteroids and appropriate antibiotics. Clinically, the horse presented as a typical heaves case however if we had only treated with corticosteroids the broncho-pneumonia would have worsened significantly and potentially caused the death of the patient!!