Vaccines, as I have mentioned many times on this blog, are perennially controversial. Many people worry that pets are vaccinated too often. Experts voice concerns that over vaccination may lead to autoimmune disease. Leukemia and rabies vaccines in cats have been linked to cancers at the injection sites.

The obvious goal for every veterinarian and conscientious pet owner should be to vaccinate pets neither too frequently nor too rarely. In an ideal world, we would vaccinate pets exactly as often as necessary. I predict that in the future this will be the norm. But as of 2009, it is impossible to say how often pets need vaccinations.

Some facts are clear. Juveniles (puppies and kittens) need vaccines more often than adults. Animals with different lifestyles need different vaccination protocols. And most important, every individual responds differently to vaccines. Every individual therefore has unique needs.

Measuring those needs is impossible. Blood tests called titers give some idea of a pet’s response to previous vaccinations, but titers measure only half of the picture. Titers measure antibody levels in the blood. However, antibodies cannot function without another component of the immune system called cell-mediated immunity. At this time there is no way to measure cell-mediated immunity. Therefore there is no way to measure a pet’s true level of immunity to disease.

I agree that many pets are vaccinated more often than necessary. On several instances I have treated animals for autoimmune disease and wondered whether vaccines might have contributed to the problem.

However, on hundreds of instances I have treated canine parvovirus. In every single one of these cases I knew with certainty that vaccination would have prevented the problem. I never have treated a properly vaccinated dog for parvo. The vaccine works.

I euthanized a 12-week-old puppy today because of parvo. A vaccine could have saved his life if it had been administered at the right time.

Over vaccination is a bad thing. Veterinarians and pet owners should work to prevent it. But don’t forget that under vaccination is even worse.

Your best option as a pet owner is to find a good vet who will take the time to discuss the controversies surrounding vaccines. Tailor a vaccination protocol to your pet based upon his or her needs, age, and lifestyle.

Share this entry with your pawple anywhere:

• Are Pets Being Over-Vaccinated?
• Where do Vaccine-Associated Tumors Develop in Cats?
• Why Aren’t Titers Used in Lieu of Vaccines?
• What are the Rationales Behind Rabies Vaccine Schedules?
• JAVMA Study Reveals Many Vets Aren’t Following Feline Vaccination Guidelines

A reader responded to one of my recent tirades (here and here) against outdoor cats with a very reasonable question. Why, she asked, is it OK for dogs to go outside but not OK for cats?

My pal Buster, a dog, goes outside every day. But I would never dream of allowing a cat to go outside.

When Buster goes outside he is accompanied by a human. For his safety he is kept on a leash whenever he is not playing fetch in a secure area.

I would never, ever consider opening the front door for Buster to spend the afternoon outside unattended. I doubt he would make it 10 minutes on the streets of San Francisco without suffering serious trauma.

But unattended outdoor activity is standard operating procedure for many cats.

If dogs were allowed outside in the way that many cats are, veterinary emergency hospitals would be as common as gas stations or convenience stores. Canine life expectancy would drop 80%.

I know many cats who are allowed outdoors only on leash (cat harnesses and leashes are readily available at pet stores). None of these cats is likely to get into fights or be hit by cars. They are, however, at risk of contracting feline leukemia.

Cats and dogs are not equipped with the wherewithal to thrive outdoors in human society. It is our responsibility to look out for them.

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Hi Dr. Barchas,
I know that the feline rabies vaccine has been associated with fibrosarcomas at the site of injection. Is it possible for the vaccine to cause tumors in other locations? Someone told me that the three-year rabies vaccine was more likely to cause cancer – is this true?

Tera
Columbus, OH

You have asked some very good questions. I’ll do my best to answer each of them.

Vaccine-associated fibrosarcomas are cancers that develop rarely at the site of rabies or feline leukemia vaccines. They appear to occur only in cats. The cause of the tumors is very poorly understood.

The cancers develop at the site of injection. I have not seen any reports of vaccines causing tumors in distant locations. Therefore, it is extremely unlikely that your cat’s abdominal tumor was linked to a vaccine. Fibrosarcomas can develop naturally, and if your cat suffered from a fibrosarcoma in her abdomen it likely occurred spontaneously. I sincerely doubt that your decision to vaccinate your cat contributed to her death.

Three-year rabies vaccines usually contain a component called adjuvant that is designed to help stimulate the immune system. One-year vaccines generally do not contain this component. Some people have hypothesized that adjuvant contributes to fibrosaroma development. These people therefore speculate that the one-year vaccine may be less likely to cause cancer than the three-year vaccine. I have not seen conclusive proof of this.

For instance, some studies have suggested that merely inserting a needle into the skin may trigger a cascade of inflammation that ultimately leads to cancer. This implies that the adjuvant is not to blame.

Also, remember that one-year vaccines must be given three times as often as three-year vaccines. The relevant question therefore is whether one-year vaccines are three times less likely to lead to cancer.

A few years ago I attended a lecture by a representative of a company that produces one-year, non-adjuvanted feline rabies vaccines. After the lecture I cornered her (literally–she was trying to get away and I backed her into a corner) and asked the following question. I remember it verbatim.

Can you provide quantitative evidence that three-year vaccines are three times more likely to cause cancer as your one-year, non-adjuvanted vaccine?

Her answer was no. To this day I have not seen any study that proves that three one-year vaccines are safer than one three-year vaccine (if anyone is aware of such a study, please let me know).

It is unlikely that your remaining cat will develop a fibrosarcoma from her rabies vaccine. Fibrosarcomas develop in approximately one out of every 3000 – 10,000 cats that receive the vaccine. I have no reason to believe that your cat is at increased risk.

Although vaccine-associated fibrosarcomas are not common, I still recommend that you never accept a one-size-fits-all vaccination plan for your pet. Good vets always are willing to talk about the risks and benefits of vaccination. Make an informed decision.

Photo: Myriah after removal of a vaccine-associated fibrosarcoma.

Share this entry with your pawple anywhere:

• Despite Controversy There is no Doubt That Vaccines Save Lives
• JAVMA Study Reveals Many Vets Aren’t Following Feline Vaccination Guidelines
• Why is it Fair for Dogs, but not Cats, to go Outside?
• Are Oral Tumors Common in Two-Year-Old Cats?
• Why Aren’t Titers Used in Lieu of Vaccines?

Hi, I am sorry to disturb you I am just after a
moment of your time.

Northamptonshire, England

Some forms of laboratory testing, such as measuring blood sugar or checking for anemia are quite simple and can be run almost instantly in any veterinary facility.

More comprehensive testing of liver, kidney, and other organ function is available at some veterinary hospitals. Other hospitals use commercial veterinary laboratories to perform these tests.

Very advanced tests must be run at commercial laboratories. These labs generally are located in major metropolitan areas or at veterinary schools. These tests sometimes are run only on one or two days each week.

Here is what I suspect happened with your dog’s samples. Because your dog’s symptoms were vague, your vet drew a blood sample on Monday and sent it to the laboratory requesting a broad, general panel of tests. A pathologist at the laboratory likely noted abnormal cells in the blood, and reported to your vet on Tuesday afternoon that they might represent developing leukemia. Your vet relayed that information to you on Tuesday evening.

Your vet may have then determined that the best way to proceed would be to perform advanced testing on the blood. It is not surprising that this would cost extra. The initial fee that you paid was intended to cover the broad panel of tests. If more tests are performed, then additional expenses should be expected.

I suspect that the additional test that your vet desired is one called immunocytochemistry. This is a test that checks for certain proteins on cells. It can sometimes be used to distinguish cancer cells from non-cancerous cells. Most laboratories do not perform this test every day. Sometimes it can take a week or longer to get results.

I believe that in the near future many diseases, including most types of cancer, will be easily diagnosable through detection of special molecules in the blood, saliva or breath of animals. These tests will yield immediate results.

Sadly, until these tests are developed, pets and people will continue waiting through agonizing periods before diagnoses are made.

If you are anxious to find out what is happening with your dog so that you can start treating him (and I certainly understand why you would be), your best bet will be to take him to a large specialist facility with advanced in-house laboratories. There should be several of them in London.

Photo credit: Click here.

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Hi Dr. Barchas,

Lindsay
Gainesville, FL

FeLV, or Feline Leukemia Virus, is a disease of cats that is related genetically to the human AIDS virus (experts do not believe that FeLV poses a health risk to humans). It can spread from cat to cat by sharing food, water or litter. Cats that groom each other or fight with each other may pass the disease as well.

You were very wise to keep Palatka separated from the cat already living in the house. The risk of the disease spreading is very real if the two cats come into contact with each other. However, if you keep them separated and practice good hygiene, the risk is low.

I also commend your vet for wanting to re-test Palatka in a few weeks. The test for FeLV sometimes yields false positives (in other words, the test comes back positive even though the cat isn’t truly infected). As well, some cats are able to fight off and clear the disease.

Unfortunately, other cats are not able to fight off the disease. These cats develop fatal immune system problems and cancers.

Keep the two cats separated until the follow-up test. If the next test is negative, the risk to your original cat is low. Nonetheless, you may want to consider vaccinating her against FeLV (be sure to discuss vaccine-associated tumors with your vet before you take that step) as a safety precaution.

If the next test is positive, I see no reason to put Palatka to sleep. Finding her a new, single-cat, indoors-only home is a better option in my opinion.

Share this entry with your pawple anywhere:

• Why is my Cat’s Tongue Inflamed?
• Despite Controversy There is no Doubt That Vaccines Save Lives
• Why is it Fair for Dogs, but not Cats, to go Outside?
• Where do Vaccine-Associated Tumors Develop in Cats?
• JAVMA Study Reveals Many Vets Aren’t Following Feline Vaccination Guidelines