Dr. Galley,
I have a young heeling horse (4 years old) that coughs a lot when I ride him. After reading your article about the throat problems I got to worrying about him so I took him to the clinic and they put a scope up his nose and found a bunch of “blisters” in his throat (they called them some big long word….I wrote it down and then lost the paper). Could you please tell me more about them. Will he get over them? Will it hurt to use him?
Answer:
“Blisters” is a common name for a condition known as pharyngeal follicular lymphoid hyperplasia. The pharyngeal mucosa, or the tissue that lines the pharynx (throat area), is normally smooth with a normal pinkish color. This mucosal tissue contains many small islands of lymphoid tissue. When a horse, especially a young horse that has not been exposed to many of the upper respiratory viral diseases or has not been immunized against all strains of the upper respiratory viruses, is exposed to one or more of theses viruses, these areas of lymphoid tissue become inflamed as they react to the presence of the viruses. When your veterinarian performed an endoscopic exam (or a video-endoscopic exam) these enlarged whitish bumps resembled a pimple or a blister and this is the origin of the common term “blisters”.
Figure 1 is an image that was taken through the endoscope of a horse with a normal-appearing throat. You can see how smooth and pinkish the mucosa appears along the top of the picture. The arytenoid cartilages are abducted (or pulled to the sides) which occurs when the horse inhales (takes a deep breath) to let as much air as possible down the trachea and into the lungs.
When a horse is exposed to one of the upper respiratory viruses (such as Equine Rhinopneumonitis or Equine Influenza) small areas of this lymphoid tissue that are present in the mucosa become hyperplastic (which just means that they begin to enlarge and appear swollen). When the viral disease is in the early acute stage these small nodules are swollen and red and feel inflamed and sore to the horse when he swallows or takes a deep breath. This is the reason that he has a tendency to cough. Within a few days, as the horse begins to recover from the viral problem and the inflammation begins to subside, these nodules begin to quiet down and assume the appearance of round whitish nodules that look like pimples or “blisters” as you can see along the top of Figure 2. The throats of the majority of cases of team roping horses that are diagnosed with “blisters” have the appearance of Figure 2. As I mentioned, the older horses have usually been around long enough to have already developed an immunity to the viruses and seldom are diagnosed with “blisters”.
In the acute cases of these upper respiratory viral diseases the pharyngeal mucosa becomes inflamed and appears very reddened and swollen. Exercise would usually cause coughing in those horses as it would be difficult to get enough air past the sore throat and down the trachea to the lungs. Early in the course of the viral disease (while these areas are still inflamed) these “blisters” can contribute to the sore throat, coughing, and swelling that interferes with the horse’s breathing. All of us who have had a case of the flu are familiar with this feeling. As these tissues begin to quiet down, the areas of inflamed lymphoid tissue usually become the small whitish bumps that are seen in Figure 2 when visualized by endoscopic exam.
Years ago I used to try to infuse (spray or flush) medication into the pharynx (throat area) in these horses that were affected with pharyngeal follicular lymphoid hyperplasia, or “blisters”, in an attempt to treat them. This condition is very common in young racehorses and all of the racetrack practitioners had their own “secret” formulation of medications that might help to lessen the inflammation of the mucosa and get rid of the dreaded “blisters”. I even tried spraying the mucosa with a refrigerant to “freeze” the follicles. I also tried to manually disrupt the follicles with some type of surgical instrument. No matter how hard I tried I was unable to see any effect from any of the flushing or other treatments…..the horses were getting well in spite of me rather than because of me. For this reason I found myself using these treatments less and less.
Many (if not most) of the horses affected with this problem would still have some evidence of the pharyngeal follicular lymphoid hyperplasia (“blisters”) from the previous year when scoped several months later. Usually these horses had stopped coughing, showed no respiratory deficit, nor made any unusual respiratory sounds. But the best sign that the remnants of the “blisters” were not bothering the horse is that the horses were breathing normally.
Sometimes your veterinarian may prescribe an oral medication that will often relieve some of the irritation until the throat is completely healed but, in this horse’s case I would probably not worry about spraying the throat to clear up the “blisters”. Tincture of time and scientific neglect will have the horse ready to go back to the arena in a short time. In other words, he should get well in SPITE of all of your efforts to treat him and not because of them.
Thanks for the question. Go ahead and tell your partner not to worry if he coughs a little…“it ain’t ketchin’.”