Coughing is one of the most common reasons to rest your horse and, although it is usually a winter affliction, outbreaks can occur at any time.

The horse¨s airway is made up of the upper respiratory tract (URT) – the nasal passages, larynx and trachea – and the lower respiratory tract (LRT) – the lungs and the small airways (bronchi and bronchioles).

Air contains many bugs and contaminants that the horse¨s respiratory tract overcomes in two ways:

  • The mucociliary escalator – specialised cells that line the airway and filter the air before it reaches the lungs.

  • Cellular immunity – specialised lung cells that kill bacteria and inactivate viruses.

    Excessive cold or dusty air, ammonia and stress all reduce the effectiveness of these defence mechanisms, increasing the horse’s susceptibility to respiratory problems.

    Blockages

    Harsh coughing due to tracheitis (inflammation of the windpipe) is one condition that affects the URT. Coughingalso occurs if the upper airway becomes partially or wholly blocked, for example:

  • A foreign body, such as a twig, trapped in the upper airway.
  • Collapsing of the trachea, due to a congenital weakness, trauma or pressure from a tumour or abscess.
  • Excessive pressure from a strangles abscess in the lymph nodes in the throat.

    Too much mucus

    Coughing is more commonly linked with LRT conditions, which may be viral, bacterial, parasitic, fungal or allergic.

    The horse coughs to clear the small airways in the lungs, which have become narrowed by accumulated mucus or pus or by the inflammatory swelling of the epithelial cells which line them.

    Spasm of the smooth muscles in the airway walls, caused by inflammation, is also a factor.

    Other signs can range from a mild nasal discharge and slightly reduced performance to a severe flu-like picture with fever, depression and anorexia.

    All coughs need careful treatment and a reassessment of stable management to avoid irreversible damage to the horse’s airways.