By Dr. Becker
Today, I have a very special guest returning for a second time to talk with us and give us the tremendous benefit of his knowledge, Dr. Ronald Schultz.
Dr. Schultz heads up the Department of Pathobiological Sciences at the University of Wisconsin-Madison School of Veterinary Medicine. He’s joining me today on behalf of an important project he’s been involved with for several years – the Rabies Challenge Fund. The purpose of the fund is to determine the duration of immunity conveyed by rabies vaccines, with the goal of extending the required interval for rabies boosters to five and then to seven years.
Dr. Schultz has agreed to spend some time today, in the first half of our two-part discussion, talking about core and non-core vaccines in cats and dogs.
I asked him first to briefly explain the difference between the two types of vaccines.
Core versus Non-Core Vaccines
Dr. Schultz replied that several years ago, the American Association of Feline Practitioners (AAFP) decided to look at all the USDA-licensed vaccines that were available for cats. They put them into categories, with the first and most important category being the core vaccines, which are those vaccines that every cat should receive.
Then they went back over the list looking for vaccines that should not be given to any cat, and placed those in a category called not-recommended vaccines.
All remaining vaccines on the list – those that didn’t fall into either the core or not-recommended vaccine categories – were placed in a third category called non-core or optional vaccines. These were to be given based on individual need, after considering a number of factors. So that’s how categories of vaccines came into existence.
The Feline Leukemia Virus (FeLV) Vaccine: Should Every Cat Receive It?
In the most updated feline vaccination guidelines, the feline leukemia virus (FeLV) vaccine has been moved from the non-core to the core category for kittens. Dr. Schultz says he would like to see every kitten receive two doses of the vaccine, administered from two to six weeks apart. (If the interval is longer than six weeks, you must start the protocol over.) He feels that with those two doses and a re-vaccination at one year, we can immunize a large percentage of the cat population against feline leukemia.
Dr. Schultz says the new guidelines recommend revaccination (after the kitten series and the one-year booster) every two to three years, but he doesn’t believe boosters after age one are necessary – especially given the development of age-related resistance.
I asked Dr. Schultz if he thinks even strictly indoor cats with no exposure to other cats should receive the FeLV vaccine, and he thinks they should (I don’t) – mainly because indoor cats very often become outdoor cats. In situations where a cat truly will never go outside or be exposed to other cats, there’s no need for the vaccine. But in Dr. Schultz’s experience, even people with the best intentions don’t wind up keeping their pet indoors at all times.
Dr. Schultz points out that the goal is to achieve population immunity. If the problem of persistently viremic cats (those who carry the virus) can be eliminated through kitten vaccination programs, the disease can be extinguished. Dr. Schultz says his colleagues in Switzerland tell him they have essentially eradicated the feline leukemia virus from that country’s cat population. Switzerland is about the size of many states in the U.S., and Dr. Schultz believes we could eliminate the virus state-by-state, if we did what Switzerland did.
He says he’s been talking to colleagues in Hawaii, trying to convince them to attempt to eliminate it there, since feline leukemia has been a real problem in that state’s cat population for years. Hawaii also has a large feral population, which doesn’t mean the feral cats are any more a threat than housecats. Studies of feline leukemia in feral cats indicate that the prevalence of persistent viremia is no higher than in pet cats – in fact, it’s actually higher in pet cats.
I asked Dr. Schultz if he had concerns about the feline leukemia vaccine and vaccine-associated sarcomas. He answered that initially there were just two types of vaccines linked to injection-site sarcomas in cats, adjuvanted leukemia vaccines and adjuvanted rabies vaccines. Dr. Schultz says it’s important to keep in mind that all adverse reactions to vaccines, including the development of tumors, occur in genetically predisposed cats. In the case of an adjuvanted vaccine, that vaccine in a predisposed cat is more likely to lead to an injection-site sarcoma than a modified-live vaccine.
What About the Feline Immunodeficiency Virus (FIV) Vaccine and the Chlamydia Vaccine?
I asked Dr. Schultz about the FIV (feline immunodeficiency virus) vaccine for cats. He replied that he does not recommend it. He said when it’s used, there must be at least three doses for the primary immunization, and then annual revaccination. One of the major problems is that there are strains of FIV floating around that the vaccine doesn’t protect against.
In addition, while FIV is a concern, the percentage of infected cats is fairly low. We just don’t see it a lot. FIV isn’t even considered in reviews of what vaccines are necessary for the shelter population.
I asked Dr. Schultz about the chlamydia vaccine. He doesn’t recommend it, either. The vaccine is primarily designed to reduce the incidence of feline infectious respiratory disease complex. In the shelter population, the vaccine hasn’t been helpful, and chlamydia is rare in pet cats. There’s also a feline bordetella vaccine Dr. Schultz does not recommend, because it hasn’t proven beneficial for shelter cats.
Is There Any Need to Run Titers on Cats?
Next, I asked Dr. Schultz if he is seeing more cat owners requesting antibody titers these days. He answered that no, very few cat owners bother titering. He says he’s not sure there’s any real need to titer for cats because there’s only one disease we can effectively titer for, and that’s panleukopenia, which is essentially feline parvovirus.
Why Dr. Schultz Prefers the Term ‘Protective Antibody Testing’ to Titering
Dogs are of course a different story, and Dr. Schultz definitely recommends antibody testing. I asked him what terminology he prefers – does he even use the word “titer”? He replied that he prefers either “protective antibody testing” or simply “antibody testing” instead of titers. This is because many tests today return yes-or-no results rather than titers.
Titer tests tend to become a numbers game, whereas tests that return a result of either “yes” (the animal has antibody at a level considered protective) or “no” (the animal does not have antibody at a level considered protective) give the information everyone needs, and no one has to get mired in trying to understand what the titer numbers truly mean. It’s much less confusing and should help veterinarians and pet owners make better decisions about revaccinations.
As I discussed with Dr. Jean Dodds in a recent interview, the whole subject of titers is tremendously confusing. Many veterinarians recommend revaccinations because they simply can’t sort out titer test results. They feel it’s easier to just revaccinate – especially when boarding kennels and grooming salons that receive titer test results often don’t understand them or accept them as proof of a dog’s immunity.
Vaccination or Revaccination Is NOT a Guarantee of Protection Against Disease
Dr. Schultz points out that what many people fail to understand is that vaccination or revaccination is by no means an assurance that the animal is protected. He has seen dogs that have been vaccinated repeatedly who have no antibody. When challenged (exposed to a disease), they are susceptible. And that includes rabies vaccines. Dr. Schultz has seen dogs that have been vaccinated five or more times against rabies that have no antibody. In the case of rabies, distemper and parvo, if there’s no antibody, the animal is not protected.
To demonstrate that fact, and to demonstrate that dogs can have lifelong immunity after receiving distemper and parvo vaccines, he keeps them in a distemper and parvo-free environment after their puppy shots. He does not revaccinate them. Seven years later, he checks their antibody levels. If there is antibody present, he challenges them with the virulent virus itself, and they survive it. If they don’t have antibody, he doesn’t challenge them because there’s a high likelihood they will get sick and die.
The presence of antibody, even at low levels, means the immune memory response will kick in and within hours the dog’s body will bring the infection under control. There will be infection, but it won’t cause disease. There’s a big difference between infection and disease. And in fact, reinfection without disease isn’t a bad thing because it leads to natural stimulation of the immune response. A few vaccines can provide sterile immunity. It is called this because the antibody produced is able to completely prevent the virus from infecting the animal, and so can’t reproduce itself. Vaccines that provide sterile immunity are almost always against viruses that produce systemic rather than local disease.
So for example, parvo and distemper vaccines provide sterile immunity for life in most cases, similar to measles, mumps, and rubella vaccines in humans. Dr. Schultz uses the example of his own case of measles when he was 5 years old. There were no measles vaccines back then. But 50 years later, he had his blood drawn for a demonstration for his veterinary students. He sent the blood to the State Laboratory of Hygiene at the University of Wisconsin and they performed a variety of serologic tests. His measles antibody response came back at a level considered protective. Now, how did Dr. Schultz have protective immunity 50 years after being naturally immunized with measles? He can thank his memory effector B cells.
Dr. Schultz explains the discovery of these long-lived plasma cells is fairly recent. They reside in bone marrow and are programmed to continue to produce antibody. A dog that lives on average 15 years will still have long-lived cells that produce antibodies to distemper or parvo at the age of 15.
Useless Vaccines and Why Some Are Still on the Market
The good news is that distemper and parvo are really the only two life-threatening canine diseases still active in our environment. Giardia, for example, is an unfortunate disease, but it’s not life-threatening. And according to Dr. Schultz, the really good news is that the giardia vaccine is no longer on the market.
I asked him about the dental plaque vaccine, and he said there’s more good news – it’s no longer on the market, either. It was in clinical trials under USDA authorization for four years. At the end of the four years, when they looked at the results, it was clear the vaccine didn’t work. It was taken off the market, and according to Dr. Schultz, credit is due Pfizer, the manufacturer of the vaccine, because they were willing to pull it.
I asked Dr. Schultz why he thinks some of these totally unnecessary vaccines ever enter the marketplace to begin with. He believes that very often there is some potential for those vaccines to provide benefit. But he also feels it’s critical that there’s a test period that actually determines whether vaccines do or don’t meet the requirements for licensure. Dr. Schultz believes the USDA is looking much more carefully at those types of vaccines now than they used to because these days we understand much more about what immunity is, how to measure it, how it protects us, and how it translates into an effective vaccine.
Dr. Schultz says one of his “favorite” vaccines is the canine coronavirus vaccine. He calls it “a vaccine in search of a disease.” This vaccine came into being back in the late 1970s when canine parvovirus first appeared. No one recognized parvo yet, but dogs were getting sick and many of them also happened to have coronavirus.
As it turns out, every animal has coronavirus -- even puppies. Dr. Schultz says it’s actually a beneficial virus. It doesn’t cause disease by itself. When scientists finally discovered the minute, spherical virus we now know as parvovirus, they found what was making the dogs sick. Meanwhile, Dr. Schultz and some of his colleagues were able to demonstrate that corona, in coexistence with parvo, could enhance the virulence of parvo.
In the 1990s, Dr. Schultz published studies that looked at what benefit the canine coronavirus vaccine might provide in the case of even a dual infection. What it provided was… nothing. But the vaccine still exists even though it has no value. Why? Because veterinarians still buy it. As Dr. Schultz explains, the only thing that removes a licensed vaccine from the market is if the manufacturer discontinues it. That’s what happened to the giardia vaccine and the porphyromonas (dental plaque) vaccine.
So if your vet says your dog needs the canine coronavirus vaccine, you can argue against it because you know its history.
Stay Tuned for Part 2 of My Interview with Dr. Ron Schultz
Stay tuned for the second half of my discussion with Dr. Ron Schultz on Friday, in which we’ll cover many more vaccine-related topics and also talk about his wonderful work with the Rabies Challenge fund.
Mercola Healthy Pets is proud to partner with the Rabies Challenge Fund to raise money to help improve the lives of animals. This week, for every $1 donated to the Rabies Challenge Fund by a Mercola Healthy Pets reader, we will donate $2, up to $30,000. I hope you’ll join us in helping RabiesChallengeFund.org fund the remaining research needed to complete their seven-year study.