Brenda
Salisbury, NC

The debate over frequency of vaccination in pets has raged since my first day of vet school. This debate is no longer as heated and fervent as it was in the past.

On one side of the debate are vets who point out, correctly, that annual vaccinations radically improved pets’ lives by preventing dreaded diseases such as feline panleukopenia (which is the original, and still the worst parvovirus) and canine parvovirus (which is believed to be a mutated form of the feline virus). If you doubt this, you have never witnessed either parvovirus wipe out a shelter or cat colony.

On the other side of the debate are the ever growing number of vets who agree that vaccines save pets’ lives, but who feel that over-vaccinating puts pets at risk of other problems without leading to significant health benefits. They point to numerous duration of immunity studies that indicate pets need their core vaccines (rabies and distemper/hepatitis/parvovirus/parainfluenza (DHPP) in dogs; rhinotracheitis/calicivirus/panleukopenia (RCP) in indoor cats; rabies where legally required in cats; RCP and feline leukemia in outdoor cats) at most every three years as adults.

Those who favor three year vaccines have grown in number steadily over the last decade. Most veterinary schools and well-respected organizations such as the American Animal Hospital Association and the American Association of Feline Practitioners back three year vaccines. The preponderance of the scientific evidence backs three year vaccines. Virtually every veterinarian who graduated from vet school in the last 15 years (including yours truly) supports three year vaccination protocols (although any thoughtful vet will concede that protocols should vary based upon an individual pet’s circumstances and lifestyle).

Brenda, I have a few thoughts about your situation. First, you should be aware that the Bordetella vaccine is controversial. There are experts who feel that it is highly beneficial to pets. There also are experts who feel it is useless. Most vets, including me, believe that it can help to reduce the frequency and severity of kennel cough in dogs but that it by no means provides complete protection.

If your Malipoo had all of his puppy shots, then the chances of him ever contracting distemper or parvovirus are essentially nil. I see no reason for him to receive the DHPP vaccine annually. In my opinion a three year schedule is more appropriate. Talk to your vet about skipping add-ons to the DHPP such as coronavirus and leptospirosis as well. (Leptospirosis is contagious to people. The vaccine against leptospirosis is appropriate for some, but not all dogs.)

Finally, I believe there is a chance that your dog’s illness last year was vaccine-related. In my opinion it is a solid reason to push for a minimal vaccine protocol in your pet.

Photo credit: some person who names himself or herself only as “me”. Seriously, folks, how am I supposed to offer photo credits when that is all you give me?

National report — The number of rabies-infected cats was almost four times that of rabies-infected dogs in the United States in 2008, according to a new report from the American Veterinary Medical Association.
Cats may be more prone to rabies because they’re vaccinated less and roam outdoors unsupervised more often than dogs, the report suggests.

The data, collected by the Centers for Disease Control and Prevention, appears in a new AVMA rabies backgrounder published online in advance of World Rabies Day, Sept. 28. The report also covers the history of rabies and its prevalence around the world as well as clinical signs, diagnosis, treatment and euthanasia protocols for infected and possibly infected animals.

Most rabies infections — 93 percent — are seen in wild animals, according to the report, but most post-exposure rabies prophylaxis (PEP) in humans is administered because of exposure to rabid or possibly rabid cats and dogs.

Researchers also warn that imported dogs carry the threat of a resurgence of canine rabies variants in this country. They point to a rabid puppy that arrived from India in 2007, and a rabid dog from Iraq imported into New Jersey in 2008.

The complete study, “Rabies surveillance in the United States during 2008” appears in the Sept. 15 issue of the Journal of the American Veterinary Medical Association.

A quick visit to the American Veterinary Medical Association’s website provided hard numbers. In 2008, 49 states (Hawaii is rabies free) and Puerto Rico reported 294 rabid cats, 75 rabid dogs, and two people with rabies. Both human cases appeared to spread by bats. Both people died.

Bear in mind that these numbers are relatively small. Rabies is not common in developed countries. However, it is a major threat to humans and animals in some parts of the world. In these areas, dogs are the leading source of human rabies.

Chart: American Veterinary Medical Association.

Marilyn
Ajijic, Mexico

Your dog’s health almost certainly does not require him to be vaccinated every year. The schedule you describe probably constitutes over vaccination.

But I don’t know that for sure. Nobody, and I mean nobody, knows the frequency of vaccination that will protect your dog from rabies. Rabies vaccines are required by law in most places. Depending upon location, vaccination schedules vary from one year to three years. Some groups are working to extend legally mandated rabies vaccination intervals to seven years. All of these schedules are based on human convenience — we can easily measure years on the calendar. However, a year (or three years, or seven years) is nothing special to a dog’s immune system.

Every dog’s response to rabies vaccination is unique. Every dog therefore should have a unique vaccination schedule.

But that is not going to happen any time soon. Governments determine vaccination schedules. And governments don’t care very much about dogs. They care first and foremost about people.

Around 50,000 people worldwide die from rabies each year. Dogs are the main vector of human rabies. That is why many places legally require rabies vaccinations in dogs.

Remember, however, that 100% of dogs who catch rabies die. Rabies vaccines certainly can save dogs’ lives.

Developing countries such as Mexico with large numbers of stray dogs have relatively high rates of rabies. Vaccination is recommended more frequently in these areas.

Your dog probably does not need to be vaccinated annually against rabies in order to be protected from the disease. But if local law requires annual vaccination, I recommend that you follow the law.

Although I don’t know exactly how often your dog needs rabies vaccines, I do know that I wouldn’t want to end up in a Mexican prison. Conditions in those facilities are famously bad. I imagine that a Mexican animal shelter would be even worse. And that is where your dog could end up if he doesn’t get his rabies vaccine — assuming that unvaccinated dogs in your area aren’t summarily shot or poisoned.

Whether or not annual vaccination is over vaccination, pragmatically speaking you have no real choice. You should obey the law.

Photo: Ltshears.

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.

However, the intermingling of children and pets poses risks for both. Here are some guidelines for protecting your offspring and your furry pals.

Unhealthy pets can spread disease to people. Children are most at risk. The diseases range from ringworm to roundworm to rabies.

However, the key phrase in the above paragraph is unhealthy pets. The risk to children from healthy pets is very low. The first guideline for safe interactions between pets and children is therefore to confirm that your pet is free of parasites and disease. Your vet can check your pet for disease by performing a physical exam and running basic tests. Broad spectrum anti-parasite medications can be used regularly to protect your children–and your pet.

Pets occasionally bite or scratch children. I have noted that many child injuries occur when an unsupervised, poorly socialized pet interacts with an unsupervised, poorly behaved child. I therefore recommend that you properly supervise and socialize your pet, and that you properly supervise and socialize your child. It’s also a good idea to keep your cat’s nails trimmed.

Injury can be a two way street when pets and children mix. Last weekend at the emergency hospital I treated several pets who wound up hurt (accidentally, of course) when left with a child. One, a Yorkshire Terrier puppy, wiggled out of a five-year-old’s arms and broke her leg. I expect her to make a full recovery. Another, a Terrier cross, was not so lucky. A child was holding her leash and she broke loose near a busy street. I don’t need to tell you what happened next. The child was inconsolable. For the sake of your pet and your child, do not allow your child to handle your pet unsupervised until he or she is able to do it safely.

Countless other pitfalls exist. Large dogs can knock children over accidentally. Pets can steal potentially toxic (to them) foods from the hands of careless children. For the sake of both children and pets, exercise common sense and practice due diligence.

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.

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“.

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.

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.

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.