Though warts may cause concern come sales time, they really are not a big dealWriting about warts in a publication such as Thoroughbred Times is somewhat like having Tim Conway play the lead role in Gary Stevens: The Movie. Well, last month you had a meatier column and next month you will have a meatier column, but this month you get warts.
As far as being a health problem in horses, warts usually fall short. The real problem is in the eye of the beholder: They are ugly (the warts, not the beholder). Ugly, but uneventful.

Cause and clinical findings
The official name of warts is papillomatosis, and the cause is the equine papilloma virus. The condition can occur in horses of any age, but is most common in young animals, those under the age of four. The usual sites of occurrence are the lips, muzzle, and around the nostrils, and may occur on the legs as a result of the horse rubbing its muzzle on them. Spread to other parts of the body and to other horses can occur via grooming, so routine cleansing of brushes, etc., is important.
Congenital warts (congenital cutaneous papillomatosis) occasionally occur and may be located in areas other than the typical ones. Although warts are most often an isolated problem occurring in one or a few horses, outbreaks involving a whole farm occur.
Incubation time is uncertain, but experimentally is found to be six-to-eight weeks. The warts grow for another six-to-eight weeks and may eventually number over 100. Most are small (a sixteenth of an inch or less), but some may reach a half-inch in diameter.
About the only thing that warts need to be differentiated from are verrucous-type sarcoids, which I have never seen so I cannot discuss them intelligently. I have read that they occur more in saddle breeds than in racing breeds, which may help to account for the fact that I have been deprived of diagnosing them.
The two main problems I have seen with wartsand neither is deleterious to a horses healthare timing and bitting. By timing, I mean that they often seem to occur in late summer, around September. This way they can be present when you try to sell your otherwise unblemished yearling. Buyers, if not turned off, are definitely sidetracked.
The other problembittingsimply involves the inability to properly seat a bit in the mouth of a horse with a heavy load of warts on its lips. This is a special inconvenience when trying to break a young horse.
The problem as perceived by many people when a horse develops a heavy case of warts is one of the horses inability to eat or breathe because of interference by the warts. I really do not think either of these actually happen, but if a client is honestly concerned, something needs to be done.

Treatment
Warts are self-limiting; i.e., they leave of their own accord two or three weeks after maturing, but things can be done to hasten their departure. Cryosurgery and heating are both successful, as is preparation of an autogenous vaccine, but these are a little on the heroic and expensive side.
There are much easier, cheaper ways to handle warts. Some people advocate smothering them in Vaseline or Ichthammol or some other thick goop. This may work; I do not know. In the case of only a few warts, the easiest method of treatment is to simply pluck them off. An easy way to do this is to make a loop with some suture material, thread, or fishing line, then place the loop over a wart and yank it tight. Voilano more wart.
In the case of many warts, removal of one at a time is still effective but time prohibitive. In these cases, the nature of warts and the horses body response to them works in your favor. Take a hemostat or even a pair of clean pliers, choose two or three of the biggest warts, and crush them. Make them bleed. It will not hurt the horse unless you reach too low and pinch some skin. Within a few days to a week or so, the other warts will start dropping off.
I have been told the reason this happens, but I will not swear to it. By making the area of the wart bleed, the virus causing the wart enters the horses bloodstream, where evidently the body recognizes it as foreign and rejects it and all of its kind; i.e., the viruses within the remaining warts. I wont promise this is exactly what happens within the horse, but the warts do leave and that is what counts.