What’s In Those “Shots?”

We are very fortunate to live in a time when vaccinations are so normal and routine that their necessity is actually being questioned by some. Only a few generations ago, humans and dogs alike lived in constant risk of developing potentially devastating diseases. Remember polio, small pox, diphtheria? Not to mention chicken pox and mumps, which today’s children no longer have to experience. Instead, a simple vaccine tricks the immune system into thinking we’ve already had those diseases, and our bodies will attack the real virus without you ever knowing it was there.

How does this work? The answer is both extremely complicated and also fairly simple. Think of the immune system as an army, and a pathogen (virus, etc.—something that causes disease) as a foreign enemy. When the army detects an invader, it sends a scouting force to check it out, evaluate it and determine the threat level. It then develops an appropriate defensive strategy and goes after the enemy to defeat it and eliminate the threat. All this takes time. In some cases, the enemy might be too fast or too powerful, and the army winds up being defeated.

But if the army already knows how the enemy thinks and what its weapons are, it can be ready to attack on short notice. The enemy might be wiped out before it ever sets foot on shore.

Vaccines work the same way. The inoculum consists of a virus, or sometimes a bacteria or toxin, which has been deactivated, or “attenuated.” This means it was altered so as not to cause disease but still triggers the immune system to mount a defense. In a way, it is like military war games, which train soldiers about enemy behavior. This inactivated pathogen “trains” the body to recognize the pathogen involved and is ready to fight quickly.

The first commonly used vaccine in dogs was against canine distemper virus and was introduced in 1950. Prior to that, distemper killed many dogs and rendered many more chronically ill, with seizures or chorea, a severe neurological disease. The original vaccine was not terribly effective by modern standards, with the effects lasting around nine months. Therefore, it was recommended that dogs be vaccinated at least once a year, and that was the standard for vaccines that followed.

Over the next couple of decades, vaccines were developed against other viral diseases common in dogs and cats. All came with the now-traditional one-year booster recommendation after an initial series of two or more primary doses. The protocol worked and was seldom questioned.

In 1979, the first three-year vaccine for rabies was introduced for both dogs and cats. It quickly gained widespread acceptance in the United States. Because rabies can be spread to humans through contact with infected dogs (in fact, worldwide, dogs are the most common source of rabies in humans), and because rabies is uniformly fatal, most, if not all, states now require that dogs be vaccinated on schedule. This isn’t because the states care about dogs—it’s to protect humans. In the United States, rabies is now very rare in dogs and humans; when it is contracted, it’s almost always through contact with wild animals. In cats and kittens, panleukopenia (so-called “feline distemper,” but not really related to the distemper virus in dogs), along with a host of viruses that caused severe upper respiratory disease, were combined into a very effective vaccine that extended the lives of pet cats to such an extent that cat overpopulation became a problem.

Cats can also be infected with rabies, but are harder to regulate. Many states have no requirement that cats receive a rabies vaccine. This is not because cats can’t get the disease or pass it to humans—they certainly can! It’s because the states can’t figure out how to enforce a law against cat owners.

In the late 1970s, a severe and highly contagious, usually fatal gastrointestinal disease swept through the world, leaving thousands of dogs dead. That disease was parvo, and it marked one of the first times in the history of the world that a new disease emerged, was identified, and vaccines developed within a few short years. Today, we still see cases of parvo in puppies, but thankfully vaccination is the norm and the disease is easy to prevent. Most cases are in non-vaccinated puppies.

In the 1980s, feline leukemia virus became a preventable disease when an effective vaccine was introduced. However, many believe the near-simultaneous introduction of reliable blood tests for the disease was equally responsible for the dramatic downturn in this deadly, widespread retrovirus of cats.

So the decades passed, and veterinarians—who remembered distemper, remembered when parvo was new, and had cried with cat owners whose cats fell one by one to leukemia virus or who lost whole litters to panleukopenia—continued to recommend annual vaccination against these diseases, because it was the best way we knew to prevent these scourges from returning.

All these diseases are still out there. All of them still infect pets in the Coachella Valley. But most are now so uncommon that many pet owners have no idea why their pets need “shots.” The viruses listed above, with a few others, constitute the so-called “core vaccine” protocols recommended today.

The typical core vaccine protocol today:

Puppies

Starting at age 6 to 8 weeks: DA2P = distemper, parvo, and hepatitis (adenovirus 1&2); repeat every 3 weeks until age 15 weeks or more. Booster every 3 years. Rabies at 4 months, one year later, then every 3 years. (This is required by law.)

Kittens

Starting at age 6 to 8 weeks: FVRCP = feline viral rhinotracheitis, calicivirus, and panleukopenia. Repeat every 3 weeks until 14 weeks or older. Rabies at 4 months, one year later, then depending on lifestyle and owner preference.

As you might imagine, over the past 60-plus years, vaccine technology has improved significantly. So have laboratory tests, and our ability to treat these terrible diseases when they occur. Still, prevention remains far better than treatment. We also know that unvaccinated pets of all ages are vulnerable to these infections. We know what puppies and kittens need to optimize their protection. What is less clear is just how often adult pets need to receive boosters.

As you might imagine, over the past 60-plus years, vaccine technology has improved significantly, and prevention remains far better than treatment.

Adult Boosters

As mentioned, vaccine technology has improved dramatically since the 1950s, when the first vaccine for canine distemper was introduced. As the technology improved, most veterinarians suspected that the protection they provided would probably last longer than the one year recommended by the manufacturers.

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Yet, up until the past 15 to 20 years, veterinarians were loathe to change the recommendation for annual boosters. It was widely assumed that yearly vaccines did no harm, and no studies existed to show us how long the protection actually lasted. With parvo still rampant throughout the world, distemper still cropping up with surprising frequency, and vaccine producers still labeling their products to be given every year, few in the trenches felt comfortable suggesting longer intervals.

Then a few cats developed malignant tumors at the location where vaccines were commonly given. First recognized in the early 1990s, within a few years it was strongly suspected that some vaccines—usually leukemia virus or rabies—occasionally cause cancer. It’s important to state that this has never actually been conclusively proven, and there are other factors involved—the tumors usually take years to appear and only a very small number of cats develop them (somewhere around 1 in 10,000 ). But it was enough to cause an upheaval in the entire industry.

Simultaneously, there was a growing suspicion that some cases of autoimmune disease in dogs might be related to vaccinations. The correlation is not strong, but since reassessment was already underway regarding cat vaccine protocols, it fell to the vaccine producers to take another look at what is really necessary to protect our pets efficiently, without risking their health in other ways.

Guidelines are still changing. The American Animal Hospital Association (AAHA)’s latest recommendations for dogs were released in 2011, but even they are based largely on unpublished material. In other words, there is still much we don’t know for sure. Keep in mind that every vaccine protocol should be tailored to the individual pet, and studies are continuing so even this might change again at any time. There seems to be relatively little difference from one vaccine manufacturer to the next, as to efficacy and duration of protection, so that remains individual preference. Most private practitioners choose the brand that seems to cause the fewest adverse reactions in their hands. I should mention that this isn’t typically the lowest-priced product on the market.

Keep in mind that every vaccine protocol should be tailored to the individual pet, and studies are continuing so protocol might change at any time.

AAHA Recommendations

Dogs, having received their puppy series as listed above, should receive vaccines for parvo, distemper, and rabies, one year after their last puppy booster, and every 3 to 5 years thereafter.

Recommendations for cats come from the American Association of Feline Practitioners (AAFP). The most recent update was published this year. According to the AAFP, “At least once a year, as part of a routine health care program, the vaccination needs of all cats should be reassessed, in conjunction with a comprehensive physical examination and consultation.” Most vets feel that vaccines become less important as cats age, and our focus turns to other aspects of their health care. However, this article is intended to address vaccination needs, therefore:

Cats having received their kitten series as listed above, should typically be boostered for rabies at least once, typically a year after their kitten vaccine; rhinotracheitis, calicivirus and panleukopenia (upper respiratory complex) at one year, and then every 3 to 5 years thereafter; and FeLV (feline leukemia virus) as kittens, one year later, and then on an as-needed basis. Cats that roam free outdoors, or are otherwise considered at high risk for exposure to feline leukemia virus (such as living with an FeLV+ cat) should be boostered every other year for FeLV.

Please remember that these are general recommendations, not gospel. You should discuss the needs of your individual pet with your veterinarian, based on his or her lifestyle.

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Another problem, of course, is that responses vary between pets, with some getting better protection than others to the exact same vaccine. It’s possible to run serum titers to assess levels of protection against most core vaccines, if you simply want assurance that your pet is protected and are willing to pay the added cost. This entails drawing a small sample of blood, which is sent off to a diagnostic lab to be tested for antibodies against the worst diseases—typically parvo and distemper in dogs, and panleukopenia in cats. Unfortunately, there are no studies showing absolute correlation between titers and protection against active disease, but we’ve been running them for enough years that many vets feel they are a good alternative to regular revaccination.

Other Vaccines

Non-core vaccines are those that are recommended only in certain situations. This discussion only pertains to dogs.

Bordatella. For dogs, most if not all vets in the Coachella Valley recommend vaccination against Bordatella bronchiseptica, which causes infectious tracheobronchitis, often referred to as kennel cough. Unfortunately, because it’s a bacteria rather than a virus, this vaccine is somewhat less protective than core vaccines. Most now recommend two vaccines, at about 8 and 12 weeks, then revaccination every year, or sometimes more often.

Snake Bite. Another non-core canine vaccine frequently recommended is Crotalus atrox, the so-called rattlesnake vaccine. This is an attenuated toxin meant to protect dogs from the adverse effects associated with being bitten by a rattlesnake. Because snake bites are quite common here in the desert, this is a good idea for some. Unfortunately, there are no studies showing that it really works, and the adverse reaction rate is somewhat higher than with other vaccines, which prevents most of us from making blanket recommendations. Talk to your vet if you think this might be useful for your dog. The vaccine is not recommended for cats.

Canine Influenza. This viral disease was introduced from Asia early this century, and is actually caused by two related but distinct viruses. It has since spread throughout the country, including here in the desert. It is readily spread from one dog to another, especially in kennels, dog parks, and other places where dogs from different backgrounds meet up and interact. It’s still uncommon in Southern California, but is expected to increase over time.

The big problem is that many dogs show either no symptoms, or nonspecific signs such as coughing. But a small number of infected dogs become very ill, and it can be fatal even with treatment—and treatment, as you might expect, is symptomatic for the most part. Like so many other viral diseases, we have no way to predict which dogs will be asymptomatic and which might become very sick, if infected. The decision whether to vaccinate depends on likely exposure. Unlike human influenza, the canine version thus far remains stable, rather than constantly mutating. This has enabled the production of consistently protective vaccines. The vaccine itself is not only effective but very safe – adverse reactions are extremely rare. Dogs receive two doses, three weeks apart, the first time they are vaccinated, then a yearly booster. Talk to your vet about whether this is appropriate for your dog.

Leptospirosis. This is a group of bacteria that can cause severe disease in dogs, typically causing high fever, along with liver and/or kidney failure. Most cases are associated with exposure to wildlife or swine, and it’s extremely uncommon in Southern California. Vaccination is based on lifestyle. The scariest thing about the disease is that humans can catch it through exposure to dog urine, as well as wildlife or swine. This fact is sometimes used to persuade people to vaccinate dogs that are at very low risk of exposure.

Lyme Disease (Borrelia burgdorferi). Typically carried by deer ticks, this disease is caused by bacteria found mostly in the northern and northeastern United States. It gained a lot of attention in the 1990s because of human cases. The vaccine is somewhat controversial in that it has never been proven to prevent disease, and some experts question whether dogs are really at risk. Nevertheless, if you plan to travel to an area where Lyme disease is common, consider having your dog vaccinated. A better approach might be a good tick preventive, because Lyme is the least of the diseases your dog might catch from ticks in California! The others—ehrlichiosis and anaplasmosis, for example—don’t get the press, because no vaccines exist and humans aren’t affected.

A number of other vaccines are occasionally recommended for both dogs and cats, but I suspect I’ve confused you enough already. For more information, visit aahanet.org/library or catvets.com/guidelines to read the full text of the most recent vaccination recommendations.

Lillian Roberts, DVM, is the owner of Country Club Animal Clinic, which is located at 36869 Cook Street in Palm Desert. (760) 776-7555 countryclubdvm.com

Quick Reference

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Puppies

Starting at age 6 to 8 weeks: DA2P = distemper, parvo, and hepatitis (adenovirus 1&2); repeat every 3 weeks until age 15 weeks or more. Booster every 3 years. Rabies at 4 months, one year later, then every 3 years. (This is required by law.)

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Kittens

Starting at age 6 to 8 weeks: FVRCP = feline viral rhinotracheitis, calicivirus, and panleukopenia. Repeat every 3 weeks until 14 weeks or older. Rabies at 4 months, one year later, then depending on lifestyle and owner preference.

American Animal Hospital Association (AAHA) Recommendations

Dogs, having received their puppy series as listed previously, should receive vaccines for parvo, distemper, and rabies, one year after their last puppy booster, and every 3 to 5 years thereafter.

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American Association of Feline Practitioners (AAFP) Recommendations

Cats having received their kitten series as listed above, should typically be boostered for rabies at least once, typically a year after their kitten vaccine; rhinotracheitis, calicivirus and panleukopenia (upper respiratory complex) at one year, and then every 3 to 5 years thereafter; and FeLV (feline leukemia virus) as kittens, one year later, and then on an as-needed basis. Cats that roam free outdoors, or are otherwise considered at high risk for exposure to feline leukemia virus (such as living with an FeLV+ cat) should be boostered every other year for FeLV.