[back] Cancer and vaccines
September 18. 2002 6:30AM
Vets focus on vaccine, cancer link in pets
By CINDY SWIRKO
Sun staff writer
Before Dr. Patti Gordon
will vaccinate a pet at her All Cats HealthCare Clinic, the owner must sign a waiver
acknowledging a link between cancer and certain vaccinations.
And when Gordon does give the shot, it may be low on one of Tiger's legs.
"I give them way far down in those legs so that if there is a sarcoma, amputation is usually more of a financially affordable alternative than radiation and chemo," Gordon said. "We are over-vaccinating, I think. There are a ton of vaccines, but not everything is necessary."
Links between vaccinations and subsequent cancers and autoimmune diseases have changed the frequency and the methods of vaccination among many area veterinarians and Alachua County Animal Services.
For instance, the vast majority of pet owners in Alachua County now get their cats and dogs a rabies vaccine that lasts three years - an option made available in the county in 2000 in part to reduce the threat of diseases, said Dr. Randy Caligiuri, director of Alachua County Animal Services.
But experts say pet owners should be more aware of the potential problems from vaccinations and discuss them with their veterinarian.
"People need to talk with their vet and consider the risk factors - including the sex of the animal, whether the cats are indoor or outdoor," said Dr. Janet Yamamoto, a University of Florida College of Veterinary Medicine professor. "Vets need to vaccinate as needed and not over-vaccinate. Not all vaccines need to be given annually."
Cats that are strictly indoors, for instance, and have no contact with outdoor cats do not need certain vaccinations, she said.
Yamamoto developed the first feline AIDS vaccine. But she said even that vaccine should not routinely be given. Instead, it should be given only to cats at greater risk of feline AIDS, such as those that go outside or males, which get in more fights.
Vaccination-related cancer is limited to cats. It is often associated with vaccines that use a killed virus rather than a modified live virus to develop immunity. Killed-virus vaccines are most commonly used for rabies and feline leukemia.
The cancer culprit may be the "adjuvant" that is used in killed-virus vaccines. The adjuvant is a material that holds the virus in the area of the shot for a few weeks so it can be time-released slowly.
The adjuvant is believed to sometimes cause fibrosarcomas - deep-rooted tumors - at the spot of vaccination.
Studies vary widely on the rate of fibrosarcomas - anywhere from one-in-1,000 to 1-in-10,000 vaccines administered.
But veterinarians say the tumors are difficult to treat.
"I personally lost a cat to fibrosarcoma," Caligiuri said. "I've done my share of taking out the tumors and they always come back. Without irradiating it or pretty much killing the cat with these other treatments, they are going to come back. When you look at the general population, it is not that bad, but it is a trend that vaccinating too often with adjuvanted stuff in cats can cause cancer."
While companies that make vaccines recommend they be given yearly, veterinarians said the vaccines typically provide longer protection.
Knowing that, some veterinarians will forego the manufacturing recommendation and vaccinate less frequently.
"If you have a good veterinarian, they will tell you that you don't have to do it annually, that every two to three years is sufficient," Yamamoto said. "The companies have tried to help by combining multiple vaccines into a single vaccine so therefore you get vaccinated one time. The less immunization, the less exposure to the adjuvant."
Some companies are now marketing adjuvant-free vaccines, but veterinarians say the products haven't been out long enough to determine if they are safe.
And Gordon said she has seen sarcomas from modified live-virus vaccines and steroid injections. She said research is now focusing on whether some cats have a genetic predisposition to the tumors.
Dogs, meanwhile, are believed to be subject to autoimmune diseases from vaccines. Researchers believe the vaccines may trigger the production of antibodies that attack the dog's own tissue, blood cells or other systems. Vaccines, for instance, have been linked to a type of anemia.
Cindy Swirko can be reached at 374-5024 or swirkoc@ gvillesun.com.