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Keep An Eye Out: Three Common Equine Cancers

Though cancer is less common in horses than in humans, it's still possible for equines to develop various forms of the deadly disease. Because horses are so large, it can be difficult to actually locate the cancer that is affecting the horse. The most obvious signs of equine cancer are typically scaly areas of hair loss, growing and changing lumps, and swollen lymph nodes, but cancer can also take on other forms.

At its most basic, cancer is the uncontrolled growth of abnormal cells. The three main types of cancer found in horses include:

Melanomas. Melanoma is the type of cancer most people visualize when they think of cancer in horses. This cancer causes skin tumors; it's estimated that nearly 80 percent of grey horses over the age of 12 will develop melanomas around the tail, perineum, sheath, eyelids or mouth. Once found, melanomas should be removed when they're still small; this is often done by laser surgery.
Sarcoids. Although a benign cancer, sarcoids can spread rapidly. There are various different forms of this cancer, each with a characteristic appearance. To add to the trickiness of the disease, individual sarcoids can change forms. Though the growth rate and number of tumors per horse can vary, the tumors tend to grow in size and multiply over time.
Sarcoids can be found nearly anywhere on the horse, but the location of some tumors make them more-difficult to treat. Treatment may include chemotherapy, radiation and surgery. Sarcoids should be treated early; the bigger the sarcoids become, the harder they are to treat. Once a horse has developed a sarcoid, it is prone to developing more, even if they are removed.
Squamous Cell Carcinoma. Squamous Cell Carcinoma generally affects horse's eyes, eyelids and penis. Though slow growing, this cancer is invasive and can spread internally. Treatment generally includes surgery, radiation or chemotherapy; early diagnosis and treatment is key. Older geldings are more prone to the penile form of this cancer; regular sheath inspection can help locate lesions before they become extensive.

New Type Of Equine Wart Discovered

A new type of equine wart has been identified by a New Zealand researcher. Equine warts are caused by the equine papillomavirus, which may contribute to the development of some types of skin cancer.

A 10-year-old Warmblood had two round, thick masses nearly 1 inch in diameter on the back of his left front fetlock; his treating veterinarian biopsied them, thinking they were sarcoids, which would have been difficult to treat in that area.

The biopsy results showed that the growths were actually warts, which typically go away by themselves. There are multiple types of papillomaviruses; they are divided into categories based on what type of lesion they cause. The papillomavirus that caused these warts, however, was new. The type of papillomavirus it is most similar to causes self-resolving warts.

The horse was treated with a topical chemotherapy drug and the lesions disappeared within a month. The veterinarians on the case noted that the cream may not have been the cure for the warts and that they may have gone away on their own.

Though not every lesion caused by the equine papillomavirus needs to be biopsied, in this case it was the correct approach as the masses were not recognized as warts. It's important for vets to remember that warts can sometimes present with an unusual appearance, the treating vet noted.

Specific Plants Show Promise In Reducing Equine Tumors

Equine sarcoids are the most prevalent skin tumors in horses, followed by malignant melanomas. Currently, there are minimal therapies available that locally target either tumor.

Drs. Lisa Annabel Weber, Anne Funtan, Reinhard Paschke, Julien Delarocque, Jutta Kalbitz, Jessica Meißner, Karsten Feige, Manfred Kietzmann and Jessika-Maximiliane Cavalleri created a study to determine if acid derived from some plants would kill the cancer cells.

They determined that flowering quince, white birch, rosemary and members of the persimmon family can be used to make an acid that kills cancer cells by directly effecting their mitochondria.

Betulinic acid occurs when betulin is oxidized; the researchers created a study to see if botulin and betulinic acid worked as a topical treatment possibility against sarcoids and melanomas. After being treated for 48 hours, the number of necrotic cells was less than 2 percent in both melanoma and sarcoid cells.

They determined that both botulin and betulinic acid inhibited the growth of sarcoid and melanoma cells in a lab setting. They recommend that additional studies be done in live horses to fully assess the anti-tumor effects of topically applied acid. Treatment regimens including short application intervals for long lengths of time could make the acid more concentrated and effective.

Read the full study here.