Page 78 - Speedhorse May 2019

WARTS AND SARCOID TUMORS IN HORSES
“There are six types of sarcoid: occult, verrucous, nodular, fibroblastic, mixed forms and malignant.”
by Heather Smith Thomas
Warts and sarcoid lumps are common skin growths in horses and may be hard to differ- entiate because they can be similar in appearance.
Andrew D. Smith, DVM, PhD, DACVS-LA, Clinical Assistant Professor of the Department of Large Animal Clinical Sciences at the University of Florida College of Veterinary Medicine, says most warts are seen on young horses, usually around the nose and muzzle, and these are generally a temporary problem. “Here at our hospital we only see the chal- lenging cases from veterinarians who refer them to us. Most of the time, the warts that occur in younger animals are not a problem,” he says.
“Most of these are associated with equine papil- loma virus 1, but they can have several forms or sub- categories. We also see aural plaques, which are warts in the ears, which also don’t tend to regress.
“Here at our hospital, we rarely see the most common ones unless that horse is coming in for some other reason like lameness, colic or some other prob- lem. If the horse also happens to have warts, we show them to our students and tell them this is what warts look like and explain that at this point we tend to just leave them alone. Within a couple of months those warts will regress, and the horse will have a lifelong immunity and never get warts again.”
These warts are contagious in that they can be transmitted between horses or spread by flies or some sort of fomite that takes the virus from one horse to another, such as grooming tools or tack used on multiple horses. “Usually if a farm has one young horse with warts, there will soon be many with warts,” says Smith. “The whole group of year- lings may have warts,”
Those warts usually don’t become a problem unless they become so large or numerous around the mouth and muzzle that they interfere with eating, breathing, or use of a bit. “We usually don’t have to treat this type of warts,” he says.
Warts on the penis are more problematic. “If a horse is referred to me for treatment, it is usually because the warts involve the entire glans penis,” he explains. “We usually have to remove those by freez- ing them or doing a partial phallectomy (removal
of part of the penis). This may be a little drastic,
but horses with partial phallectomies do very well. Treating them any other way doesn’t get to the root of the problem to get rid of them.
“If these warts are small and localized, we can freeze them or remove them with a laser. If we do a partial phallectomy, the horse would not be useable for breeding so we do those only in geldings. A partial phallectomy doesn’t work very well in stallions. If they get an erection during the first couple months while those tissues are still healing, this increases
the risk for surgical site dehiscence (rupturing) and breaking the sutures.
“Hypothetically, you might be able to do this surgery on a stallion and still be able to collect him if you were able to keep him from getting an erection until the surgical site was fully healed, but I don’t know of anyone who has done that. Usually, you’d find the warts earlier in a breeding stallion and be able to remove them before they become so large that a partial phallectomy would be necessary, because someone is looking at the penis more often than just twice a year.”
A gelding is more likely to end up with larger growths before they are discovered. In early stages, the penile warts could be removed with a laser or by freezing, and the stallion would be able to continue breeding. Usually those warts start out with just
one or two, but by the time you see this in a geld- ing there might be 50, or it may have progressed to squamous cell carcinoma. A person might pull the penis out to clean it and wonder what the huge mass is. “This is usually when I see the horse,” says Smith. “They don’t send me the ones that have just one or two small warts. There are some things you can do with those early on, but those are the easy ones that I rarely get to see.”
There is also a congenital form of warts where the foal is born with them. “Those gener- ally don’t regress. They may be located on the forehead, nostrils, lower lip, and sometimes around the thorax or hind legs. These need to be removed,” he says.
The only warts that actually regress are in young horses that are normal at birth and then encounter the papilloma virus in their first year or two of life. Those warts usually appear around the face and muzzle, grow larger for a while, and then regress as the horse builds up an immunity to them. “We tell horse owners to just watch them to see if they regress. It’s usually the warts in older horses that we end up having to remove surgically.”
Heather Smith Thomas
76 SPEEDHORSE, May 2019
EQUINE HEALTH