Vaccinations and feline cancer

 Dr. Liz Ruelle is a certified feline specialist and owner of Wild Rose Cat Clinic in southeast Calgary.

Dr. Liz Ruelle is a certified feline specialist and owner of Wild Rose Cat Clinic in southeast Calgary.

By Jacqueline Louie

Vaccinations help animals live healthier, longer lives by preventing potentially fatal infectious diseases. But, like any aspect of medicine, vaccines need to be used appropriately to ensure they’re contributing to your cat’s optimum health.

With vaccination protocols tailored to meet the needs of the individual cat, veterinarians advocate for the regular vaccination of all cats, indoors and outdoors, says Dr. Liz Ruelle, certified feline specialist through the American Board of Veterinary Practitioners and owner of Wild Rose Cat Clinic in southeast Calgary.

“Infectious diseases are all around, and not going away any time soon,” explains Dr. Ruelle. “That said, vaccinations are not without risk. The most common side effects from vaccines are similar to those in people — a mild ache at the injection site and a day of malaise. One very rare, but albeit serious risk of vaccination, is the development of a soft tissue tumour (cancer) known as an injection-site sarcoma.”

Injection site sarcomas were first seen in cats in the late 1980s. Although initially linked with vaccinations, injection-site sarcomas have now been associated with a variety of commonly used, and life saving, injectable medications in cats.

When a person or animal receives an injection, there is a local inflammatory reaction at the injection site. In a normal patient, that local inflammation soon calms down, but in those rare cats who are genetically primed to develop an injection-site sarcoma, the inflammation becomes chronic, and they can go on to develop a tumour.

“There is no way to predict which cat will form a sarcoma, as the underlying risk factors are at the DNA level and thus not detectable on examination or patient history,” Dr. Ruelle says. When a patient forms a sarcoma, there is often no way to know what was the underlying trigger, as sarcomas can develop years after an injection; they can also develop in cats without any history of having received an injection (vaccine or other).

“This is why the causes of cancer are not black and white, in both human and veterinary medicine,” Ruelle says, noting that cancer is a multi-factorial disease that encompasses everything from an individual’s environment, to their genetics to their lifestyle.

“Vaccines still are really important,” she adds, noting that vaccines protect against diseases that can be deadly, such as rabies, and for the vast majority of the cat population vaccines are hugely beneficial. For instance, thanks to both improved vaccinations and screening tools, veterinarians typically don’t see feline leukemia virus as often any more.

“You hear stories from vets in the 1980s, when the feline leukemia virus was absolutely rampant. Now I rarely see it in practice, because we have had good dedicated vaccine and testing protocols,” Ruelle says.

The current vaccine philosophy, she explains, is that “we want more cats vaccinated, but to vaccinate each individual less often. It’s balancing risk between appropriate disease protection and patient safety.”

When choosing the appropriate protocol for an individual cat, a veterinarian takes into account factors such as disease exposure risk, patient age and health status. Newer vaccines are much more effective, substantially safer and are a very important part of cat health.

Dr. Ruelle says: “If you have concerns about vaccination risk, or the risk of any treatment plan for that matter, then that’s a conversation you need to have with your veterinarian.  Medical decisions, even the most routine ones, are made after careful discussion between owner and doctor.”

The most common cancer that Dr. Ruelle currently sees in her feline patients is intestinal lymphoma — a cancer type common in her older patients, unrelated to both vaccinations and infectious disease. “Just like in people, cancer is a disease that’s of higher risk as a cat gets older and as the cell’s “photocopier” gets worn out and DNA starts to get damaged.

“Just like people, for optimal health and cancer prevention it’s all about ensuring that cells stay healthy — but that is easier said than done,” she says. “Lifestyle factors that owners can control include feeding their cat an appropriate diet, maintaining an ideal weight, minimizing toxin exposure (such as second-hand smoke), and routine veterinary care to catch disease changes early.”

10 subtle signs of sickness in cats

One or more of these “10 subtle signs of sickness” could be a sign of stress. And Dr. Liz Ruelle, a feline specialist practicing at Wild Rose Cat Clinic in Calgary recommends calling your veterinarian if you notice anything amiss with your kitty. “Know what the status quo is with your cat, and if you’re seeing a change, and especially if you see one or more of the top 10 signs of sickness, then that’s a reason to be calling your vet,” she says.

10 subtle signs of sickness:

  • Inappropriate elimination behaviour: urinating or defecating outside the litter box
  • Changes in interactions: A social cat not wanting to be touched or a cat that is not typically cuddly wanting to be cuddled
  • Changes in activity levels, either up or down
  • Changes in sleeping habits
  • Changes in water intake
  • Increased or decreased water or food consumption
  • Unexplained weight loss
  • Changes in grooming habits
  • Changes in vocalization
  • Bad breath

For more information about caring for your cats, visit the American Association of Feline Practitioners at and click on “Cat Owners” on the navigation bar or visit Wild Rose Cat Clinic at