While cancer is not as common in horses as in dogs, cats and people, it still poses a health risk for our equine companions. Many cancers affecting horses are treatable, so monitoring your horse for cancer and seeking prompt veterinary care for any suspicious lumps or bumps can lead to many more healthy years together.
Four types of sarcoid cancer - flat, verrucous, nodular, and fibroblastic.
Morris Animal Foundation, with support of our donors, continues to fund critical work to change the odds for horses suffering from cancers, and it’s why we started our annual Stop Cancer Furever campaign.
© 2019 by Veterinarian Services
Approximately 80% of reported cancers in horses are associated with the skin or the tissue layer beneath the skin. The three most reported cancers in horses are squamous cell carcinoma, melanoma and sarcoid tumors.
Squamous Cell Carcinoma
It's not often we get to talk about curing cancer. Still, this possibility came closer to fruition thanks to the fantastic work of Morris Animal Foundation-funded researcher Dr. Rebecca Bellone and her team at the University of California, Davis.
The group identified a genetic mutation for eye-related squamous cell carcinoma in Haflinger horses, a breed with a higher reported incidence of SCC. Findings helped inform the development of genetic screening tests for Haflinger and other breeds, including Belgian, Rocky Mountain Horse, Connemara Pony, Holsteiner and Belgian Warmblood horses.
“The risk factor we have identified for Haflinger horses is in a gene known to repair UV-caused damage to DNA,” said Dr. Bellone. “We recommend using a UV-protecting fly mask on horses with two copies of the mutation. This is just one example of how understanding the genes involved can be used to reduce the risk of cancer.”
In another ongoing study, researchers from Colorado State University are tackling SCC in horses from a different angle – investigating a novel treatment using a drug successfully used to treat a similar disease in people. In this small-scale study, the team hopes to show that this drug can also improve outcomes in affected horses and, if successful, will use findings to further study this novel SCC treatment.
Quick facts about SCC in horses:
The most common type of tumor affecting the eye and eye structure of the horse.
The second most common cancer found in horses.
Usually locally invasive and slow to spread but can result in blindness
Often related to sun exposure and more prevalent in regions where solar radiation (ultraviolet rays) is higher
Providing shade for your animals can lower the risk
Most often diagnosed in horses 12 years and older
A high recurrence rate following treatment requires vigilant monitoring
Melanoma
Melanoma is one of the most common types of skin tumors found on horses. This form of cancer is especially prevalent in gray horses, reaching an incidence rate of up to 80%. The tumors, which can be benign or malignant, often are advanced by the time they are diagnosed and can result in prolonged and significant discomfort for affected horses.
Unfortunately, veterinarians often instruct many horse owners to adopt a "wait and see" approach when it comes to cancer. One Morris Animal Foundation-funded researcher decided to challenge this approach.
Dr. Jeffrey Phillips, an Assistant Professor of Oncology and Medical Genetics at Lincoln Memorial University in Tennessee, set out to find practical ways to treat horses with melanoma. He had an interesting proposal – use a recently developed canine melanoma vaccine to treat horses with the disease. Phillips devised a treatment protocol for horses and received a grant from the Foundation for a clinical trial.
His study was a stunning success. Most horses in the study (the initial study enrolled 15 horses) experienced dramatic tumor shrinkage, while the remaining patients had their tumor growth slowed, as he demonstrated. The horses also developed antitumor immune responses following vaccination. Phillips’ results provide hope for thousands of owners whose horses struggle with this debilitating cancer.
Quick facts about melanoma in horses:
Appears as growth in or under the skin
Affects about 80% of older gray horses
In non-gray horses, melanoma tends to be more dangerous
Arabians and Lipizzaner horses reportedly exhibit a higher prevalence of the disease.
Typical tumor sites include the underside of the tail, genital areas and head.
Canine melanoma vaccine shows promise as treatment for equine melanoma
Sarcoid Tumors
Sarcoid tumors are the most common skin cancer diagnosed in horses and ponies. The good news is these tumors are nonmalignant (they don’t spread to other parts of the body) and seldom fatal. However, they can grow quite large and spread and multiply locally, impacting the quality of life for affected animals.
Sarcoid tumors come in all shapes and sizes. They can look like circular hairless areas of skin, round lumps, warts or combinations. They can occur on any part of the horse's body but are more common near the genitals, head or underside of the abdomen. Tumors also can pop up at sites of previous injuries or scarring.
A recently completed Foundation-funded study is taking an unusual approach to treating sarcoids by using a modified virus usually found in chickens to attack the sarcoid cells. The team showed that the modified virus could infect the cancer cells and kill them. The team hopes to use their findings to develop a new immunotherapy.
Quick facts about sarcoids in horses:
Most common tumor in horses
Found anywhere on the body
Often challenging to treat
Seldom fatal, but can prevent riding if tumors develop in the saddle or bridle area
Several sarcoid tumor subtypes with some horses having a mixed combination
A possible link between the development of tumors and infection with bovine papillomavirus
Science to Save Animals Starts with YOU!
Cancer studies like these take vision as well as financial investment. That’s why Morris Animal Foundation, with the generous support of our donors, continues to fund this critical work to change the odds for horses suffering from these devastating cancers. And it’s why we started our annual Stop Cancer Furever campaign.
We need your help.
You can fuel twice as much lifesaving animal cancer research with your donation today, thanks to Petco Love and Blue Buffalo, who are matching all gifts dollar for dollar, now through June 30, 2024, up to $100,000.
Together, we can Stop Cancer Furever.
Press release by Morris Animal Foundation