Vaccination: Which ones do they REALLY NEED, and HOW OFTEN?

by Ann Brightman

When Helena took her new Sheltie puppy, Mick, to the vet for his first check-up, she felt more than a little anxious when it came time for him to receive his shots. While she wanted to protect her new friend from deadly diseases like distemper and parvo, she was also concerned about the health risks associated with over-vaccination. Although Helena went ahead with the vaccines and follow-up boosters, she was worried about subjecting Mick to subsequent annual shots, even though her vet told her she was risking her dog’s health even more by not doing so.

It’s a common quandary these days, especially as we hear more and more about the often devastating side effects of over-vaccination. How do we prevent our dogs or cats from contracting infectious diseases that can often be fatal, while also protecting them from the equally serious health consequences of too many shots? The best strategy is to learn which vaccines are absolutely necessary (referred to as core vaccines), why they’re needed, and what the minimum requirements are for each to ensure protection from disease without over-vaccinating.

WHAT ARE CORE VACCINES?

“Core vaccines are those that every dog or cat should receive, regardless of geographic location or lifestyle,” says Dr. Ron Schultz, Professor and Chair of the Department of Pathological Studies at the University of Wisconsin-Madison’s School of Veterinary Medicine. For dogs, the four core vaccines are canine distemper (CDV), canine parvovirus-2 (CPV-2), canine adenovirus-2 (CAV-2) and rabies. Those for cats are feline panleukopenia or parvovirus (FPV), feline herpesvirus-1 (FHV-1), also referred to as feline viral rhinotracheitis, feline calicivirus (FCV) and rabies. In this article, the first in a three-part series, we’ll be taking a close-up look at canine distemper, feline panleukopenia and rabies. The eight vaccinations listed above are considered core because the diseases they protect against are distributed over a wide area and have a high mortality rate. “These vaccinations are absolutely necessary,” says Dr. Schultz. “You want the vaccine to be the first antigens to prime the immune system. You don’t want to leave it up to natural immunization or exposure.” This is because, when compared to the actual disease-causing virus, the vaccine is a safer way to protect the animal. “If the vaccine is live, it’s attenuated. If it’s killed, it can’t cause disease,” explains Dr. Schultz. “It’s true that many puppies that never see a vet get naturally immunized by exposure to distemper, as an example, but for every one that gets vaccinated, probably another would have died if the first encounter with distemper occurred prior to vaccination.”

MINIMIZING VACCINATION

Although core vaccines are necessary to protect your companion from infectious disease, even these do not need to be given on an annual basis. “That’s what we’re trying to change,” says Dr. Schultz. “What we recommend is that both puppies and kittens get the core vaccines at least once at or over the age of 12 weeks.” The 12 weeks is significant, because prior to that, many animals still have passive maternal antibodies that block immunization, which means they may not respond to the vaccine and are therefore unprotected against the disease. American Association Hospital Association (AAHA) guidelines recommend vaccinating again at one year, and once every three years after that, although even that may not be necessary. “I have studies that show duration of immunity at seven to nine years for all the core vaccines except rabies, and even on an antibody basis I can show that rabies gives much longer protection than three years,” says Dr. Schultz.

CANINE DISTEMPER

(CDV) CDV is a highly infectious and often fatal disease that attacks the respiratory, gastrointestinal and central nervous systems. Although dogs of any age can contract distemper, puppies up to six months of age are most susceptible to the disease, which can cause a range of symptoms from fever, loss of appetite and eye inflammation in its early stages, to diarrhea, vomiting, pneumonia, and neurological complications such as ataxia, seizures and paralysis. Canine distemper occurs around the world not only among domesticated dogs, but also in many wild carnivores such as raccoons, skunks and foxes. “Wildlife is actually now more of a reservoir for distemper than dogs are,” says Dr. Schultz. “The virus is spread mainly by air, or by direct contact with secretions from the infected animal. The mortality rate among puppies with distemper is 50% or higher.” On the plus side, the distemper virus is very fragile and easily destroyed by outside influences. “It doesn’t live very long in the environment,” says Dr. Schultz. “It dies very quickly because it is what we call an enveloped virus. These kinds of viruses are highly susceptible to water, disinfectant and sunlight.” Although there is only one distemper serotype, there are several genotypes. “What this means is that, from an immunologic standpoint, it doesn’t matter which distemper infects the animal, they’re all similar; the vaccine for canine distemper can protect against the different genotypes.” Dr. Schultz adds that modified live vaccines (MLV) are most effective for distemper. “In fact there’s no question in my mind that you should be using live vaccines for most of the cores. Although attenuated, live vaccines infect and replicate, and that’s how you get immunity.” Although AAHA recommends vaccinating against distemper every three years after the initial puppy shots, challenge studies have shown that the minimum duration of immunity can last five to seven years, and perhaps even longer. In fact, titers have indicated that dogs can be protected for nine to 15 years. “To be honest, although canine distemper is a core vaccine, I think a dog only needs to receive it once in his life,” says Dr. Schultz. “The same goes for canine parvo and adenovirus-2. That’s the vaccination program I’ve been practicing on my own dogs without any difficulty whatsoever. We’ve never had a vaccine-preventable disease occur.” Titer testing is highly effective for canine distemper, but according to Dr. Schultz, the best time to do it is at two weeks or more after the last puppy vaccination, to ensure that the animal responded to its initial vaccines. “To my mind, that’s the only time it’s of medical benefit to use a titer test for canine distemper. After that, you don’t really need to titer the animal since you can easily go five or seven years before the next vaccine.”

FELINE PANLEUKOPENIA (FPV)

Although FPV is sometimes referred to as feline distemper, this terminology is misleading. “When I talk about feline ‘distemper,’ I always talk about it as feline parvo or panleukopenia,” explains Dr. Schultz. “The virus that causes this disease is essentially identical to the canine parvo virus, but not the canine distemper virus. If a dog has parvo, it can infect a cat, but this doesn’t happen with distemper.” Most often found in kittens, FPV is a contagious and deadly disease that attacks and destroys growing cells in the intestine, blood and nervous system. It causes diarrhea, vomiting, a lowered white blood cell count, and neurological symptoms such as tremors. Kittens up to six months of age can easily die from the disease, while older cats may develop much milder signs. “There’s a tremendous age-related resistance to parvo,” says Dr. Schultz. “If the animal is less than a year old, mortality is 80% to 100%. However, I rarely see mortality in animals over a year of age, although I might see mild morbidity. Nevertheless, feline parvo is the one cat vaccin4e I absolutely insist on.” Like canine distemper, feline parvo has worldwide distribution with outbreaks occurring most commonly in urban areas during the summer months. The disease is transmitted by direct contact, although cats can also contract FPV from the fecal matter of an infected feline. Unlike canine distemper, the parvo virus is extremely long-lived, and can remain active in the environment for months or even longer. “Parvo is what we call a naked virus and is one of the most resistant,” says Dr. Schultz. Soil contaminated with the parvo virus still has the ability to infect an animal a year later. “In fact, parvo is more often caused by environmental contamination than direct contact with an infected animal. You don’t need the infected cat to be in the environment for very long in order for it to leave the virus behind.” As with canine distemper, MLV vaccines are very effective for preventing feline panleukopenia. “With parvo, in fact, you’d better be using live vaccines, because the killeds don’t work.” As with other core vaccines, kittens should be vaccinated at 12 weeks. Titer testing is very effective for this disease, although challenge studies indicate that a vaccinated kitten can remain protected from feline parvo for eight years. RABIES (RV) Unlike distemper and parvo, rabies is a disease that can be transmitted from animals to humans, which is why rabies vaccinations are required by law throughout North America. The virus infects the central nervous system, causing encephalitis and death. Symptoms can include confusion, partial paralysis, aggressive behavior, excessive salivation and other neurological signs. Although rabies occurs worldwide, including in Asia, Africa and Latin America, some countries such as the U.K. are rabies-free. In North America, rabies is most prevalent in the eastern portions of the continent, although cases can occur anywhere. Wild animals such as raccoons, skunks, bats and foxes are the major carriers. Because rabies isn’t age-related, mammals at all stages of life can be affected with the same degree of severity. The chief means of transmission is by a bite from an infected animal. “There are multiple strains of rabies, but the important thing is that the vaccine prevents infection with all those different strains,” says Dr. Schultz. “Although the risk of infection in domesticated animals is generally low, the public health concern is the issue. That’s what drives the regulations for rabies vaccines.” As with the other core vaccines, puppies and kittens should be vaccinated at 12 weeks. Although some states and provinces have approved a three-year rabies vaccine, some still require annual re-vaccination for dogs and cats, even though the duration of immunity based on challenge studies has been shown to be three to seven years. “The regulations vary from state to state and province to province, and even from municipality to municipality.” It’s also important to realize that a municipality might have a more restrictive requirement than the state or province it’s a part of, although not the other way around. “Rabies titers are effective, but there’s no point running them because you’re going to have to vaccinate your animal by law anyhow,” says Dr. Schultz. However, titer testing for rabies is useful in cases where the animal has had an adverse reaction to the vaccine, or has a medical condition that could be aggravated by the vaccination. “In these situations, local municipalities will sometimes accept a letter from the vet as a reason not to vaccinate every three years, But the guardian has to understand that the animal is still considered to be non-vaccinated, and if it bit someone, it would be treated as such if it’s gone beyond the three years, irrespective of the vet’s letter. Even so, if you have a dog that for health reasons shouldn’t be given a rabies vaccine, it’s better to take the chance of it being quarantined for biting someone than to give the vaccine and kill the dog.”

BACK TO BASICS

Vaccinations definitely have their place in disease prevention, but knowing where to draw the line is key. “I’ve seen it go from no vaccines back in the mid-1960s, to where we just kept adding one after the other,” says Dr. Schultz. The pendulum has since started swinging back again as organizations such as AAHA and American Association of Feline Practitioners (AAFP) began looking more closely at which vaccines out of the 12 for cats and 16 for dogs were really needed and why. “We used to have one manufacturer that made a canine vaccine combo with 13 different components in it. That’s not good, and that’s why it’s not available anymore.” Now, by contrast, companies are coming out with information demonstrating that their products give duration of immunity lasting several years. “All the major manufacturers are coming on board and saying that their core vaccines give at least three years immunity. To me, that’s the greatest gratification in the more than 25 years I’ve been doing this.”  

The following article on LD 429, An Act to Require Veterinarians to Provide Vaccine Disclosure Forms, appears in the Sunday, February 20, 2005 issue of the The Lewiston Sun Journal

Too many shots? By Bonnie Washuk, Staff Writer Sunday, February 20,2005 AUGUSTA - Like many pet owners, when Kris Christine of Alna got cards from her veterinarian reminding her that Meadow's and Butter's shots were due, she brought in her lovable Labs. Her vet recommended that her pets have rabies shots every other year and distemper shots every year, Christine said. But months after Meadow's biannual rabies shot in the fall of 2003, she noticed something. "He had this weird thing on his back hind side," she said. "Every time he'd run, it would swell, then it would go away." Meadow eventually was diagnosed with mast cell cancer, which Christine believes resulted from the vaccination injection at that same spot on his leg. "It's not something you want," she said. "It's an aggressive cancer." Veterinarians say the likelihood is very small that Meadow's cancer stemmed from the shot. However, while taking care of Meadow's cancer, Christine stumbled on a hot debate in the animal health field: How often should dogs and cats be vaccinated? While experts stress that vaccines are vital to the health of pets, mounting research indicates vaccines can no longer be considered harmless. Research shows they can cause adverse health effects - everything from lower immunity against viruses, bacteria and parasites, to cancer - and that some vaccines do not have to be given as frequently as once thought. In response, the American Animal Hospital Association in 2003 began recommending less frequent vaccinations for cats and dogs. Christine, who began researching the subject after Meadow's cancer was detected, quickly became an energetic crusader, spreading information about vaccinations and questioning frequency guidelines. She believes that by following her veterinarian's recommendations, "Meadow was being over-vaccinated for years." In the process, Christine said she discovered that Maine law required a rabies shot for dogs and cats every two years, despite the fact that the vaccine's manufacturer says it is good for three. She questioned the law in early 2004, and it was changed last fall, according to state public health veterinarian Dr. Robert Gholson. The state now mandates that rabies shots be given every three years. (Saying not all veterinarians have gotten the word, Gholson is sending out a second reminder.) Christine now hopes she will be equally successful with her next effort: to get the Legislature to pass a law requiring Maine veterinarians to disclose the pros and cons of vaccines. Rep. Peter Rines, D-Wiscasset, is sponsoring L.D. 429, and said that since introducing the bill, the outpouring of e-mails and letters in favor has been overwhelming. "In my tenure as a legislator I've never had this kind of response," he said. Pet owners are thanking him, and some people outside Maine have said they hope his bill will lead to similar laws in other states, he said. "Everyone wants to do the best thing for our four-legged friends," said Rines, noting his bill is intended only to give consumers information. But some Maine veterinarians plan to voice their opposition to the bill at its public hearing on Feb. 28. Saying they feel like they're under attack, the opponents say they see no need for disclosure forms.  The making of a crusader After Meadow was diagnosed with cancer last year, he underwent two operations. A chunk of his back thigh was removed. On the bottom of one of Christine's veterinarian bills in April for cancer treatment was a reminder that Meadow's distemper shot was due in November and his next rabies shot in 2005. It upset Christine. "I said, 'He's not going to be alive then.'" Christine said her veterinarian said the cancer did not come from the vaccine, but Christine was skeptical. She grew even more doubtful after learning that the law required dog immunizations every two years even though the rabies vaccine lasted three. When she got the bill, Christine told her vet she had a problem giving her dog vaccinations every year or every other year. "Here's my dog lying at my feet, suffering with a huge chunk of his hind leg removed. I thought, 'You were giving him medication that you know he doesn't need.'" Christine found a new veterinarian and became an advocate for changing the laws and making pet owners more aware of the potential health risks posed by vaccinations. "We need the tools," she said. She is not the only one who feels that way. Among those concerned about pets receiving vaccinations too frequently are AKC judge and former breeder Arnold Woolf of Lewiston and Larry Doyon of Munster Abbey Kennels in Minot, breeders of German shepherds. Both say they support the legislation. Experts: Risks are low, but . . . Christine's efforts have also met angry opposition. Last week the Maine Veterinary Medical Association came out against L.D. 429. In a Feb. 2 letter to lawmakers, MVMA President Matt Townsend did not directly spell out why the organization is opposed to the bill. But Townsend complained that such a law would mandate "cumbersome disclosure and consent procedures for every vaccination and medication dispensed by veterinarians." It also said Christine "has launched what can only be described as an aggressive scare campaign, designed to drive a wedge of distrust between pet owners and their veterinarians." Actually, the law makes no mention of medication other than vaccines. The law says veterinarians must provide disclosure forms informing consumers about the advantages and disadvantages of vaccines. MVMA Executive Director Bill Bell said there is no Maine protocol on how often vaccines should be administered, and that even top researchers disagree. "The bill is vague to the point of being ridiculous," he said. Veterinarians are worried a disclosure form would scare away some pet owners from having their dogs and cats vaccinated, which would lead to diseases coming back, Bell said. He added that the bill will increase paperwork for veterinarians without doing any good. One nationally recognized vaccine researcher, Dr. Ronald Schultz, favors the law. While rare, vaccines can cause adverse health affects in cats and dogs, said Schultz, an expert in animal vaccinations and chair of the department of pathobiological sciences at the University of Wisconsin School of Veterinary Medicine. "I favor anything that would better inform the potential buyer of what they need and what they're getting," he said in a telephone interview from his Wisconsin office. A majority of veterinarians are already providing that information, but some are not, he said. The thinking that vaccines are harmless is changing, Schultz said, adding that annual vaccinations don't help pets, and can hurt them. "For years we worked under a philosophy of 'if it doesn't help, (at least) it won't hurt.'" What he called "an awakening" began in the 1980s when healthy cats given vaccines were getting cancer. "The odds were small, but if the odds are 1 in 1,000 that doesn't matter if it's your pet," he said. The probability of dog vaccines causing cancer is lower than cats, he said. "But we're constantly learning. The wake-up call to the veterinarian profession was that vaccines create a risk. ... No matter how rare the adverse effects are, we don't want to give a product that's not needed." Schultz said the veterinary profession has been using annual or biannual shots as a way to bring clients through the door for the more important exam. Convincing pet owners to come in by telling them their pets' annual or biannual shots are due should no longer be practiced, he said. Schultz cited the newest guidelines from the American Animal Hospital Association, which in 2003 went from recommending annual distemper shots to one every three years. Under the guidelines, dogs and cats should receive core shots for rabies and distemper beginning at 12 weeks, a booster at one year, then boosters no more frequently than every three years. (Some central and western Maine veterinarians are following the recommendations, others are not. See related chart.) All other vaccines are "optional," according to Schultz and the AAHA, and are based on the animal's lifestyle and risk. For instance, annual Lyme disease and heartworm vaccines may be important for pets living in areas where those diseases have been prevalent, but may not be necessary where they have not, he said.