Chronic Cough without Fever in Horses
Robert N. Oglesby, DVM

Introduction

This is a common problem in horses and can be a challenge to
diagnose. In spite of many possible causes their are two which
are most likely: mold dust in the hay and recovering upper
respiratory tract infection.

Physical Exam: Horse and Hay

Whenever a horse presents with a cough a thorough exam is
warranted. The most common causes may be difficult to prove with
an exam but more serious causes can be eliminated. Temperature,
examination and palpation of the throat, auscultation of heart
and lungs, and a look at the hay should all be done. If he horse
has been nonresponsive to treatment then an endoscopic exam of
the pharynx, larynx and trachea is warranted. This will help rule
out inflammatory problems there.

A developing allergy to hay mold and recovery from a viral
infection are two common causes of a cough with few other
clinical signs. Careful exam and history along with examination
of the hay will usually lead you to the correct answer. Contrast
these differences:


1. While exercising, the cough from hay allergies improve but the
cough from a recovering infection will worsen. The exercise and
coughing helps the horse clear out the secretions caused by the
allergy but will irritate the pharyngitis.

2. The horse with pharyngitis will sometimes demonstrate
sensitivity to laryngeal and upper tracheal palpation while the
allergic horse may have changes in the lung sounds on
auscultation. In mild cases you may find neither.

3. Does the hay have a musty odor? When you first open the bales
do you see a little cloud of "smoke" that disappears rapidly? If
the answer to either question is yes: be suspicious of mold
allergies.


Treatment for Pharyngitis

Horse's with mild pharyngitis will respond to stall rest. Usually
21 days is plenty of time and if the cough persists beyond that
further work up is warranted. If you strongly suspected
pharyngitis, and the hay was excellent, examine the pharynx with
an endoscope. If nothing turns up on reexam try treating him for
hay allergies. Or even better, wet the hay while resting him for
the pharyngitis. Once he is over the cough begin him back on good
hay. If the cough returns when he is put back on hay you have
your culprit.


Treatment for Allergies to Hay Mold

If you suspect hay allergies, begin by removing hay from his
diet. Either leave him out on pasture, feed cubed hay, or use one
of the hay substitute feeds made for heavy horses (Sweet Rely tm.
by Manna Pro). If these are not practical you can try thoroughly
soaking the hay just prior to feeding. If the horse shows
improvement over the following week you will need to be more
careful about the quality of your horse's hay. Continued exposure
to hay that makes him cough will only make him more sensitive and
can lead to heaves.

Corticosteroids can be used to help a horse get over the effects
of exposure but must not be used as a substitute for removing the
cause.


Hay Allergies Can Progress to a PERMANENT Debilitating

Disease In the early stages of hay allergies a light cough develops that
disappears as the horse works. As the disease progresses the
horse's cough begins to worsen and then breathing becomes
difficult. What is happening is that long time exposure to the
hay molds is causing permanent changes in the lungs, reducing the
amount of air he can breath in. When a horse becomes affected to
the point of difficult breathing he is said to have heaves.