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

The other night I put a young skunk to sleep.

The skunk was captured by San Francisco’s department of Animal Care and Control. It had been behaving erratically, staggering, and acting disoriented. Animal Care and Control did not have a veterinarian on duty at the time (it was the middle of the night), so the officer brought the skunk to the emergency hospital where I was working for euthanasia (the skunk’s condition was deemed to be beyond help).

The skunk’s likely diagnosis was canine distemper virus–the same virus that causes serious disease in dogs, wild canids, marine mammals, and African lions.

For the most part, diseases tend to be species specific. Dogs most often catch diseases from other dogs. Cats catch diseases from other cats. Humans catch diseases from other humans.

But there are exceptions. Rabies is the most famous exception. The virus can infect any mammal. Many parasitic worms can infest multiple species. Feline toxoplasmosis can infect humans, sea otters, and wild cats. Canine distemper virus can infect a variety of wild animals.

Fortunately, basic hygiene and vaccinations can protect your pet from many wildlife-borne diseases.

Pets who have minimal exposure to other members of their species (such as indoor cats and small dogs that rarely go out) may still be at risk for exposure to wildlife. Talk to your vet about these risks, and make life style and vaccination decisions accordingly.

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• Despite Controversy There is no Doubt That Vaccines Save Lives
• Out-of-Date Rabies Vaccine Lands Dog in the Clink
• What are the Rationales Behind Rabies Vaccine Schedules?
• Seriously, how Often do Dogs Need Rabies Vaccines?
• How Often Should Dogs Receive Rabies Vaccines?

Molly was minding her own business when the raccoon attacked her. The poor dog didn’t see it coming.

The sweet nine-year-old Yorkshire Terrier stepped out of her owner’s back door for her bedtime bathroom break. She rounded the corner. The owner heard a commotion, and the bloodied dog scampered back to the safety of the home. If her tail had been more than a stub, it certainly would have been between her legs. The incident lasted just a few seconds.

When I treated Molly I found several bite wounds on her face and muzzle. She also had three or four puncture wounds on her rear end. From her injuries, it appeared that she had run headlong into the raccoon. The raccoon savaged her face. The dog turned to run away, and was tagged a few times on her rump during the escape.

Fortunately, the injuries were not serious. But legal matters threw an additional wrench into the gears of the evening. After animal attacks I am required to determine the victim’s rabies vaccination status. I wish the owner had lied.

Molly lived the life of a homebody. She lived mostly indoors. The owner had decided to forego rabies vaccination for several years. Her vaccines were overdue.

Molly’s chances of contracting rabies during the encounter were basically nil. But San Mateo County law still dictates that pets with overdue rabies vaccines must be quarantined for six months after wild animal encounters. Five and one half months of the quarantine can take place at home. But the first 14 days must take place at the San Mateo animal shelter.

I’ve never been to that shelter. But I can’t imagine Molly is happy there. I feel bad for her–none of this was her fault.

Photo: “Bastique“.

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• Despite Controversy There is no Doubt That Vaccines Save Lives
• Wild Animals Can Spread Disease to Pets
• What are the Rationales Behind Rabies Vaccine Schedules?
• Seriously, how Often do Dogs Need Rabies Vaccines?
• How Often Should Dogs Receive Rabies Vaccines?

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?

Dr Barchas,

Randy
San Diego

A minimal vaccination schedule depends upon a dog’s age and lifestyle. In a mature dog, a minimal vaccination schedule would mean avoiding optional injections such as the ones that protect against Bordetella, canine coronavirus, and probably leptospirosis (but talk to your vet about this one first–leptospirosis can spread to humans). Mature dogs generally need vaccines no more often than once every three years. In some cases it may be safe to push vaccines other than rabies (see my previous post) back to once every five years or longer. You will have to find a vet who will take the time to work with you to tailor a vaccine schedule that is appropriate for your dog.

Titers are blood tests that are performed to assess immunity. Titers measure a component of the immune system called antibodies that circulate in the blood. They are reported as a ratio of one to a number. The higher that number, the better. A titer of 1:5 is low. A titer of 1:1,000,000 is very high.

Your vet may have been concerned about using your dog’s titers because the titers were low. Or, he may have been concerned by something else: nobody knows how to interpret titers. I am not aware of any studies that show what titer is required to prevent infection with rabies, distemper, or parvovirus. A low titer likely implies susceptibility to disease and a high titer likely implies immunity.

However, we do not know the most crucial piece of information that is necessary for interpreting titers. We do not know the minimum titer measurement that correlates with protection from disease.

There is another factor that complicates the use of titers. Titers measure only half of the immune system. Although it is very useful to know the quantity of antibodies circulating in the bloodstream, antibodies cannot work alone. They depend upon a different portion of the immune system (called cell-mediated immunity) to get the job done. At this time, I am not aware of any way to test cell-mediated immunity.

Consider this analogy. Antibodies are like foot soldiers in the battle against disease. Cell-mediated immunity represents logistics and weaponry. If your dog has a high titer against rabies, that is the equivalent to having a huge army of soldiers ready to battle the disease. But it matters whether the soldiers are armed with high caliber weapons and advanced communications, or whether they are disorganized and can fight only by throwing dirt clods.

Without the ability to measure cell-mediated immunity, one cannot truly know whether a pet is protected against the disease in question.

In general, high titers likely are correlated to strong cell-mediated immunity. I strongly believe that in the future either titers or other tests of immunity will supplant regular vaccinations in pets. I am confident (perhaps optimistic would be a better word) that in the next half decade we will see some major advances in immunology that will lead to decreased animal vaccinations and increased use of immunological assays.

But for now, although titers provide significant information, they do not look set to revolutionize veterinary medicine.

Photo: Jeffrey M. Vinocur

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Rabies vaccination became a discussion in a dog park . . .

Fred
Pleasanton, CA

The Vet Blog has not touched upon vaccines in a while. Vaccines seem to be second only to food when it comes to causing controversy on this blog. Now that most of us seem to have recovered from the raw food disucssion, I think it is time to open up a new can of worms.

Tomorrow’s post will discuss the use of titers in lieu of vaccines. Today, let’s talk about rabies vaccines.

Rabies is among the most dreaded human diseases. According to the ultimate repository of human knowledge, Wikipedia, the disease kills 55,000 people each year. Untreated rabies has the distinction of being the most deadly disease known to mankind–mortality is 100%.

Until the advent of rabies vaccines, dogs were by far the leading source of human rabies. In areas where canine rabies vaccination is common, human rabies is very rare. Most human rabies cases occur in developing countries where pets do not routinely receive vaccines. In many of these countries, the mainstay of rabies control is mass slaughter of dogs during outbreaks. Poisoned meatballs were recently used in an attempt to control a rabies outbreak in Bali. In 2006, tens of thousands of dogs in China were killed in an attempt to halt a rabies outbreak.

Pets receive rabies vaccines to prevent the disease from spreading to humans. And given the events in Bali and China it is clear that rabies vaccination, in general, saves the lives of pets–both through prevention of rabies (which is 100% fatal in dogs and cats) and prevention of mass slaughters.

But . . . there is a highly relevant but.

In the United States rabies vaccines are administered by veterinarians to dogs (and sometimes cats) as required by law. Rabies vaccination laws are developed by state or local governments. And once the government gets involved, reason goes out the window.

Some rabies vaccines are labelled only for one year use. These must be given every year. Other rabies vaccines are labelled for three year use.

Those that are labelled for three year use are subject to the laws of local governments. In municipalities where annual rabies vaccination is required, the vaccine is given every year despite the label. In areas where three year vaccination is mandated, the exact same vaccine is given triannually.

There is no rhyme, reason, or hard science to back up any rabies law with which I’m familiar.

Rabies vaccination laws are capricious. This is especially true in cats. A case of rabies in a feral cat several years ago prompted San Mateo county, near San Francisco, to require rabies vaccines in all resident cats. Adjacent San Francisco county does not require feline vaccination. Rabies has not been reported in a cat in either county for several years (more than 100 years in the case of San Francisco).

In many places, rabies vaccinations administered to pets less than 16 weeks old are considered invalid even though there is no scientific basis for such a timeline. A puppy in Alaska recently exposed several people to the disease when it was younger than 16 weeks and had therefore not been vaccinated.

Rabies vaccinations have been linked, rarely, to cancers in cats. Some experts have suggested that rabies vaccination may trigger scary problems such as immune-mediated hemolytic anemia and ischemic dermatopathy in both species.

On balance, there is no doubt in my mind that rabies vaccination benefits pets and people. I’ll take the one-in-100,000 case of ischemic dermatopathy over mass culling with strychnine meatballs (or a high prevalence of human rabies) any day. But I believe that a more rational and scientific approach to rabies vaccination is in order.

The Rabies Challenge Fund is working to investigate the efficacy of rabies vaccines and promote a scientifically validated rabies vaccination schedule for pets. Perhaps some day it, and organizations like it, will lead to rabies vaccine requirements that are evidence based.

But at this point bureaucracy is carrying the day.

Photo: This photo from the CDC illustrates why pets get rabies vaccines.

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• Despite Controversy There is no Doubt That Vaccines Save Lives
• Children and Pets are Good for Each Other. Follow Basic Guidelines so Nobody Gets Hurt.
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• Out-of-Date Rabies Vaccine Lands Dog in the Clink
• Where do Vaccine-Associated Tumors Develop in Cats?

I am the first person to admit that I do not know how often pets need vaccines. I am not alone this lack of knowledge. Absolutely nobody knows how often pets need vaccines.

I do, however, sometimes feel like I am alone in my willingness to admit that I don’t have all the answers when it comes to animal vaccination. And I frequently bump heads with two groups who claim, wrongly, that they do know how often pets should be vaccinated.

Members of the first group aren’t likely to comment on this blog, but they have plenty of money to throw around. They fund “studies” and publish “scientific papers” to justify their cause. I am referring to vaccine manufacturers. Their conflict of interest is obvious. If they sell more vaccines, they make more money. I am skeptical of what they say, and I urge you to take the same attitude.

The second group uses tactics that are remarkably similar to push for the opposite agenda. This group consists of anti-vaccination activists. Members of this group publish online summaries of data that cherry-pick the scientific literature to focus on and exaggerate the risks of vaccines. They tend to ignore data that contradict their arguments. Like the vaccine manufacturers, their interest is not in true science. They are promoting an agenda. I view everything they say with the same skepticism that I reserve for the companies making vaccines.

The true facts of animal vaccination are incredibly complicated. The details are phenomenally nuanced. Anyone who claims the matter is simple either does not understand the subject or is pushing an agenda.

I urge you not to heed the calls of those who claim that all pets need every vaccine every year. Equally, when someone tells you that pets never need shots, please ingest their comments with several grains of salt.

Do not let your pet fall victim to any group’s agenda.

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In 1991 veterinary medicine suffered a disturbing revelation. Two commonly used feline vaccines were linked to the development of malignant tumors at the site of vaccination. The tumors, called fibrosarcomas, are associated with the vaccines for rabies (in cats only) and feline leukemia. They are aggressive and difficult to remove. They occur in approximately one out of every 3000 – 10,000 cats who receives a rabies or leukemia vaccine.

The discovery of these so-called vaccine associated fibrosarcomas lead to the creation of a special task force (called, unsurprisingly, the Vaccine Associated Fibrosarcoma Task Force). The recommendations of the task force were supposed to cause a dramatic shift in the way cats are vaccinated.

Prior to the discovery of the fibrosarcomas and the formation of the task force, most cats were vaccinated against rabies and leukemia every year. The vaccines were administered between the shoulder blades because that is the easiest place to give injections to cats.

The task force recommended that the leukemia vaccine should be administered only to cats who spend time outdoors. The rabies vaccine should be administered as required by law. If possible, both vaccines should be administered no more frequently than once every three years.

Finally, the task force advised veterinarians to change injection sites. Fibrosarcomas between the shoulders are virtually impossible to remove. Therefore, the leukemia vaccine should be administered in the left rear leg, near the ankle. The rabies vaccine should be administered similarly in the right rear leg. If a fibrosarcoma develops in either of these locations, the cat’s life can be saved by amputating the leg–a less than perfect solution to the problem, but better than the alternative.

Vaccine associated fibrosarcomas are a source of angst for me. I have worked during my career to minimize the number of rabies and leukemia vaccines I give to cats. And I always give the vaccines in the rear legs.

However, a very disturbing paper published in the February 1, 2009 Journal of the American Veterinary Medical Association (JAVMA) indicates that many veterinarians are ignoring the recommendations of the task force and needlessly endangering the lives of their feline patients. According to the paper, significant numbers of cats are developing vaccine associated fibrosarcomas between their shoulder blades. This means that significant numbers of veterinarians are still giving rabies and leukemia vaccines in that spot.

Here are the conclusions of the paper.

Conclusions and Clinical Relevance–Despite publication of the vaccination recommendations, a high proportion of tumors still developed in the [region between the shoulder blades] . . . [v]eterinarians are complying with vaccination recommendations to some extent, but need to focus on administering vaccines as [far down] as possible on a limb to allow for compete surgical margins if amputation of a limb is required. (J Am Vet Med Assoc 2009;234:376-380)

What can you do to ensure that your vet is following the task force’s recommendations? Talk to him or her. Ask whether vaccination for leukemia and rabies is appropriate for your cat. If the vaccines are appropriate, ask where they will be administered. Never accept a one-size-fits-all approach to vaccination.

Photo: A vaccine associated fibrosarcoma between the shoulder blades of a cat, courtesy of Texas A&M’s School of Veterinary Medicine.

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• Where do Vaccine-Associated Tumors Develop in Cats?
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Hi,

Thanks
Andrea

It is not uncommon for dogs to react to vaccines in the way that yours did. Vaccines work by stimulating the immune system to fight bacteria and viruses. Some individuals react to vaccines excessively, causing lumps (called granulomas) to develop at the site of injection. These lumps generally are not life threatening. However, I always recommend minimal vaccinations in any pet that develops these sorts of lumps.

Although lumps at vaccination sites are not especially uncommon, lumps at antibiotic injection sites are much more rare. The fact that your dog reacted to both implies that his body may have a low tolerance for injections of all sorts. Perhaps the trauma of the needle penetrating the skin caused an exuberant immune system response. Or maybe the antibiotic and the vaccine both triggered inflammation at the injection sites, causing lumps to develop later.

Although I don’t know what exactly is causing your dog’s lumps, I definitely think you should avoid giving him injections if possible. Use oral antibiotics, and keep working with your vet to develop a minimalist vaccine protocol.

One final note. Pets can die from vaccines, but it happens very rarely. It is much more common, in my experience, for pets to die from lack of vaccines. I am aware of six dogs who died of parvovirus (which is preventable with vaccines) in one neighborhood of San Francisco last week. In my career I have not seen even one pet die from a vaccine reaction (although there have been two close calls).

Photo: Ginger has no known history of injection reactions.

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I have a lovely Shepherd/Retriever mix who suffered
with dreadful ear infections for years until the
fifth vet we saw finally sorted out it was
allergies. She is now on Hill’s prescription low
allergen z/d and doing very well on it.

Maggie-Lee
Christchurch, New Zealand

Two subjects tend to inspire fanaticism among people who have pets: food and vaccines. It makes sense if you think about it. Both subjects are complex enough to prevent any person from proving, definitively, that their diet or vaccine protocol is the best. I have covered both subjects several times on this blog. Click here, here, here or here to read some food-related articles. Click here, here, here, here, here, or here to read about vaccines.

No doubt about it, plenty of people believe that Hill’s z/d is manufactured by Satan himself in the bowels of Hell. But z/d isn’t even remotely unique in that regard. If you doubt that, I challenge you to pick a food, any food, and google it. I guarantee that someone, somewhere, believes the food you have picked is produced by Satan or his henchmen.

Let’s step back from satanic associations for a bit and try to suss out what’s going on with your dog. Ear infections in dogs often are related to allergies. Dogs can be allergic to many different substances. Food is one of the many substances to which dogs may be allergic. Therefore, switching your dog to a hypoallergenic diet may help his ear infections.

Dogs with food allergies react to the proteins in their diets. Wheat protein is a common cause of troubles, but it is hardly the only one.

There are two ways to make a hypoallergenic diet. A manufacturer can use “novel” protein sources such as duck, fish or rabbit combined with egg or potato. Or, a manufacturer can use chemical reactions to modify the protein in the food so allergic individuals do not react to it.

Hill’s z/d employs the second tactic. The proteins are hydrolyzed, or broken down, to a size that makes them unlikely to cause allergic reactions.

Hill’s z/d is balanced and nutritionally replete. However, it is hardly the most natural diet out there. I certainly wouldn’t be willing to eat a food in which all of the proteins had been hydrolyzed. Nonetheless, I could survive on one.

If feeding a natural diet is a priority for you, then z/d isn’t the best choice. You can talk to your vet about alternative hypoallergenic diets.

However, remember that plenty of dogs thrive on z/d. If it is the only diet that works, it’s probably better for your dog than the pain and stress of chronic ear infections.

Photo: Checkers has no known history of ear infections. But he has fantastic ears.

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