What You Should Know About Cancer In Horses

When a horse gets cancer, it is a sign that the normal mechanisms of its cell growth have changed and that the cells have proliferated in a manner that is unchecked and disorganized. This process forms cell masses that disrupt a horse’s body’s normal functioning and development.

If a cancerous growth develops deep inside the horse’s body, you may not realize it for a very long time. Gone unchecked, cancerous lumps can grow to large sizes and may spread into vital organs or press against vital organs causing shutdown and malfunction.

If a horse has a cancerous growth on or around its head, the tumor may cause the horse’s face to take on a distorted appearance. Tumors on or around the head can also interfere with your horse’s ability to breathe, eat, see and/or hear.

When cancerous growths begin to spread it is called metastasis. When a cancerous lump metastasizes, more lumps grow. This spread can be very difficult or impossible to get under control.

What Are The Symptoms Of Equine Cancer?

symptoms of equine cancer

Lumps that spread within a horse’s intestines can fill up large parts of the organs and/or spread to other organs. When this happens, your horse may begin to show signs of disease such as weakness, loss of appetite, listlessness, weight loss and many other generalized signs of illness.

A horse who has cancer of any sort may experience some or all of these symptoms:

  • Your horse may experience unexplained bleeding from rectum, nostrils or other orifice.
  • Your horse may suffer from chronic weight-loss and/or chronic diarrhea.
  • You may notice that your horse coughs frequently and non-productively.
  • Your horse may experience difficulty and pain when urinating.
  • Lumps may appear and may change or enlarge.
  • Your horse’s abdomen may become distended.
  • Your horse may go mysteriously lame.
  • Your horse may have bad breath.
  • Lymph nodes may swell.

Cancerous growths can also cause behavioral problems. For example some cancer cells cause hormone imbalances that can disrupt the horse’s behavior. If a mare develops ovarian cancer (equine granulosa) her body will produce too much testosterone. This can cause her to behave like a stallion and become aggressive to her pasture mates.

What Causes A Horse To Develop Cancer?

what causes a horse to develop cancer

It’s hard to know what causes any specific type of cancer. It is believed that most cancers are connected with genetic mutations, but research is still underway to refine and improve this belief. When researchers are certain that genetic mutations actually do cause cancer and understand how they do, it will be much easier to predict, control and treat these cancers.

Evidence suggests that melanomas are caused by genetic mutations that are linked with the color of horse’s skin and coat. Gray horses tend to develop melanoma.

These nodular masses are often found in areas of skin that have little or no hair. For example around the dock and under the tail. Other common locations include in the eye and behind the jaw.

Occasionally a melanoma will develop inside the horse’s throat or abdomen. Melanoma is not always a cause for concern. Sometimes these growths stay very small and do not cause any symptoms or problems. Occasionally they will spread throughout a horse’s body and become very invasive and dangerous tumors.

How Can You Prevent Cancer in Horses?

Steps for prevention are uncertain, but it only stands to reason that you would follow the same common sense protocols you would in preventing cancer in yourself. Be sure that your horse has a healthy, wholesome lifestyle and diet.

Avoid exposure to known carcinogens. Keep your horse well protected from excessive sun exposure.

Establish a regular schedule of veterinary visits so that your vet will have the best chance of catching cancer in its earliest stage. Early-stage diagnosis is key to successful treatment.

How Is Cancer Diagnosed In Horses?

how is cancer diagnosed in horses

For example, if your vet notices that your horse has swollen lymph nodes, he or she may want to take a biopsy or perform cytology on the lumps or nodes to find out if they are malignant.

If your vet notices that your horse is suffering from diarrhea, distended abdomen or other evidence of gastric distress, he or she may want to perform an endoscope, an ultrasound or a radiograph to locate any intestinal tumors.

Unexplained lameness, dry cough, bad breath and/or difficulty and pain with urination also indicate internal problems that may be quite serious. If your vet notices any of these symptoms, he or she will want to perform a radiograph.

How Can Horses Be Treated For Cancer?

Treatments that have worked in humans suffering from cancer often work quite well in horses with cancer. Just as with people, treatment of cancer in horses may involve surgery, vaccines and drugs and even radiotherapy and chemotherapy.

Just as with human cancer, treatments for cancer in horses are constantly developing. For example as we learn more and more about genetics, cancer treatments based in gene therapy are becoming more of a possibility for both people and horse’s.

One treatment for melanoma that has been very successful involves the creation of a vaccine based on the horse’s own tumor tissues. Small instances of skin cancer can sometimes simply be kept under control through the use of topical creams and ointments. Some horse owners have had success using cannabis oil as a topical treatment for melanoma.

Treating Equine Melanomas With Cannabis Oil – A Case Study

The treatment you and your vet choose will depend on a number of factors, including the type of cancer, your resources and your vet’s preferences. Some vets believe that surgery should never be performed because it may trigger cancer to metastasize. Other vets favor fairly noninvasive surgical techniques such as laser surgery to deal with small tumors. Work closely with your vet to determine the right course of action if your horse develops cancer.

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Horses & Foals

6022 S Drexel Ave
Chicago, IL 60637

Amazon Disclaimer

Horses & Foals is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.


Horses & Foals do not intend to provide veterinary advice. We try to help users better understand their horses; however, the content on this blog is not a substitute for veterinary guidance. For more information, please read our PRIVACY POLICY.