Rethinking Vaccinations
Vaccines Linked to Increased Numbers of Tumors in Cats

by Dr. Paige B. Garnett

At the Western States Veterinary Conference in February, 1996, Dr. Greg Ogilvie of Colorado State University presented a lecture on the latest findings on vaccine induced fibrosarcomas in cats. Cat owners need to be aware of these tumors, what seems to be causing them, and what can be done to treat them.

History

The first report of the possible link between vaccines in cats and the subsequent occurrence of tumors called fibrosarcomas was published in 1991. Historically, a vaccine for feline leukemia virus became available in 1984, and a rabies vaccine that could be given under the skin (subcutaneously) instead of in the muscle tissue also became available in 1984. These two vaccines appeared to be the ones most often linked to the occurrence of these tumors.

Incidence

Studies have indicated that the chance of a cat getting a fibrosarcoma from either a rabies vaccine or a feline leukemia vaccine is anywhere from I in 10,000 to 1 in 1,000.

Causation

Dr. Ogilvie explained the possible link between fibrosarcomas in cats and the use of aluminum in certain vaccines. Aluminum is used to extend the length of protection of the vaccine and has been linked to inflammation at the site of the vaccination. It is thought that the inflammation might later start the development of a tumor. This idea is being disputed by many of the vaccine manufacturers, who claim that tumors have developed from vaccines that don't contain aluminum as well as from those that do. There is also some evidence, Dr. Ogilvie discussed, that a cat must have a genetic predisposition to develop a tumor which is why only a few cats develop them.

Tumor Identification

The earliest a tumor has developed following a vaccination has been 3 months. They develop a firm swelling under the skin that grows very rapidly. Any time a cat owner finds a lump on their cat, it is important to have their veterinarian examine the mass to determine if it is serious or not. Often, a small biopsy will be taken to determine whether the mass is a tumor or not, and if it is a tumor whether or not it is a fibrosarcoma.

What If A Cat Has A Fibrosarcoma Identified?

The oncology (cancer) department at Colorado State University has developed a three fold plan to treat fibrosarcomas. These tumors are very invasive - which has made their treatment difficult. A deep, wide surgery is performed, followed by radiation therapy and then a course of chemotherapy. Without aggressive treatment, these tumors continue to grow and invade the cat's body and do lead to the death of the cat. Treating these tumors aggressively when they are small has the greatest chance for successful cure.

What Can Be Done To Prevent Such Tumors?

Recently, the American Veterinary Medical Association has recommended that veterinarians put the various vaccinations in different locations in cats to better monitor the individual vaccinations and to discourage tumor formation (the more vaccinations in one single site the greater the chance for a tumor to develop.) Discuss with your veterinarian what vaccines your cat should get, and stay informed as more and more information is discovered to explain these tumors.