Feline skin cancer

Are the vaccines that protect against deadly diseases putting your cat a risk for skin tumors?

You're a caring cat owner. You take your feline to the veterinarian religiously at the same time each year for a thorough annual examination. And during that checkup a set of initial vaccinations or booster shots is usually administered. But exactly how safe are vaccinations? Frankly, many veterinarians and researchers aren't quite sure. Over the last several years, evidence has surfaced to suggest that injections may actually cause skin cancer in some cats.

In 1991 veterinary pathologist Mattie Hendrick uncovered a mystery. Conducting a series of studies at the University of Pennsylvania School of Veterinary Medicine, she noticed "highly aggressive" and malignant tumors (known as fibrosaromas) forming in cats. Hendrick and her colleagues noted that the lesions nearly always appeared at the most common site of vaccinations: between the shoulder blades.

Felines diagnosed with malignant skin cancer need a lengthy treatment program of chemotherapy, surgery, and radiation. Without treatment, most cats die. But while Hendrick's discovery may be unsettling, veterinarians are even more concerned that the more than 50 million American cat owners, fearing sarcomas, may forgo vaccinations and the routine examinations that accompany them--unwittingly putting their felines at greater risk of illness. Skipping shots, both first-time vaccinations and boosters, veterinarians stress, can be far more dangerous than the risk of vaccine-induced sarcomas.

Fibrosarcoma in cats is certainly not a new phenomenon, nor is it rare, says veterinarian Douglas Brum, director of the Animal Wellness Program at Angell [Memorial Animal Hospital in Boston, a division of the Massachusetts Society for the Prevention of Cruelty to Animals/American Humane Education Society. But the majority of skin cancers are not linked to vaccines. Instances of vaccine-associated feline sarcoma appear only infrequently-approximately 2 in every 10,000-and when they do, the two highest-risk injections are those for rabies and feline leukemia.

"But I can guarantee you that if it's your cat that develops sarcoma, you won't care what the odds are," says veterinarian Tom Elston, a member of the Vaccine-Associated Feline Sarcoma Task Force, a coalition of concerned national veterinary organizations that includes the American Veterinary Medical Association and the American Association of Feline Practitioners. The task force was formed, in part, to investigate the cause, recommend new treatment protocols to veterinarians, and help inform pharmaceutical companies that manufacture the vaccines. "This is a matter that deserves very serious consideration," says Elston, who runs his own private animal practice in Irvine, California. "What no vet wants is to do something that is supposed to help, only to find out it ends up hurting the cat."

The task force has met four times in the last year in an effort to get to the bottom of what may be causing the the cancerous lesions. "It's true that studies are showing the killed-rabies-virus and killed-leukemia-virus vaccines to be a problem," says Elston. "It's much less a problem with the panleukopenia vaccine." Elston says that although most of the sarcomas in question have developed between the shoulder blades, there is no evidence to strongly support the hypothesis that the problem is linked to the trauma of multiple injections at the same site.

"We're looking at many factors, including needle size, the speed of the injection, as well as the adjuvant [the chemical additive dispensed with the dead virus to stimulate the immune system]," says Elston. "It does seem that some cats appear prone to a reaction to the adjuvant," the content of which varies among the 10 pharmaceutical companies manufacturing the vaccines. Some researchers speculate that the aluminum contained in certain vaccines may deform healthy skin cells. Tumors, however, are occurring in nonaluminum shots as well, says Elston: "We haven't completely ruled it out yet, but it doesn't seem to be a direct factor."

Elston also notes that sarcomas have also developed at the site of antibiotics and worm medications administered via injection. He believes it will take years to solve the mystery. The task force is seeking funds for further research, and many of the pharmaceutical companies seem eager to contribute.

In the meantime, Elston suggests cat owners request their veterinarians to vaccinate in different parts of the body and chart these locations. Some animal experts recommend administering shots in a rear leg, since the sarcomas that form between the shoulders are very difficult to operate on and even more difficult to keep from coming back. The risk of sarcoma is not decreased, but amputation becomes a treatment option, according to Patricia Olson, director of veterinary affairs for the American Humane Association.

Some animal experts recommend that for the time being you ask your veterinarian for aluminum-free injections as well as "modified live FVRCP" vaccinations (a three-in-one shot for feline panleukopenia, feline calicivirus, and feline viral rhinotracheitis). The rabies and feline leukemia vaccines are in dead-virus form, and epiclenliologists are still examining potential links between dead-virus formulas and sarcomas.

The good news: "Vaccines may be lasting longer than we thought," says Elston, signaling that new protocols may call for more widely spaced vaccinations. In addition, intranasal vaccinations may take the place of injectable vaccinations in the very near future. In the meantime, feline specialists recommend that eat owners keep a close eve on injection sites. A sarcoma can appear anywhere from 12 weeks to three years after a shot.

While the potential sarcoma link is being investigated, veterinarians are reassuring cat owners that there is good reason to continue vaccinating their pets.

Newborn kittens do not have fully active immune systems, making them vulnerable to several diseases, says Brum. As kittens nurse from their mothers, however, they ingest antibody-rich colostrum, which Brum says helps boost their ability to fight off infection--at least for the first several weeks of life. By the time they become about 6 or 8 weeks old, kittens no longer benefit from their mothers' colostrum and need inoculations to stimulate their immune systems, particularly against the most common respiratory viruses. Residual antibodies from the mother's colostrum can actually prevent vaccinations from doing their job, making an extra booster every 3 to 4 weeks, up to 16 weeks of age, advisable.

What if you have just adopted a kitten and discover that vaccinations have been delayed or ignored for the first 12 weeks? Or what if you have just taken in a stray adult whose shot status is unknown? Veterinarians suggest two full sets of inoculations for upper respiratory diseases and panleukopenia, three to four weeks apart.

A common misconception among eat owners is the belief that only eats who venture outdoors need vaccinations. But even house eats can be exposed to rabies via infected bats and other animals that find their way into your home, not to mention the airborne viruses that can be carried inside via dust or your own clothing. So which inoculations does your eat need? The following list can help you sort through the available vaccines:

Feline Respiratory Disease (Rhinotracheitis, Calicivirus). These upper respiratory tract diseases are extremely contagious, says Brum, and widely spread from eat to eat, making the chances of infection for your feline quite high. Though not necessarily fatal, they can lead to further complications. There is a vaccination, and veterinarians usually administer a combination shot for these illnesses and panleukopenia. Most kittens, however, will need two to three boosters. Current recommendations still call for yearly shots for adults, although this may soon change.

A vaccine for chlamydia virus, also a respiratory disease, is available, although its efficacy remains debatable.

Feline Panleukopenia. Also known as distemper, this gastrointestinal-tract disease is highly transmissible from eat to eat. Without medical attention, 9 out of 10 eats with distemper die, and even with costly and prolonged treatment fatalities occur. Symptoms include loss of appetite, fever, depression, vomiting, and diarrhea. Fortunately, this ailment is nearly 100 percent preventable with a vaccine, says Brum. Recommendations are the same as those listed for the combination feline respiratory diseases vaccine above.