Pet Vaccines 104 - How Often Should You Vaccinate?

Try these links for previous articles in the series on canine vaccines, feline vaccines, and how vaccines work.

You've probably had many vaccines yourself - vaccines for measles, mumps, hepatitis, tetanus and more. And if you're like me, you're likely hard pressed to remember what you've had and when... but you probably remember several sore arms spaced throughout life. Every vaccine varies in effectiveness and duration, meaning sometimes you need a vaccine once (measels), annually (flu), or every several years (tetanus). This article will attempt to demystify some of the when of vaccines for your dog and cat.

The Vaccine Schedule
For those who just wandered by looking for the recommended vaccine schedule without a burning need for the why behind those recommendations, let's get it out of the way:

• Puppies 
• Distemper, Hepatits, Parvovirus (DAP): every 3-4 weeks, from 6-16 weeks old
• Rabies: once at 12-16 weeks
• Bordetella (optional, but recommended for puppies): intranasal once at first vaccine appointment
• Leptospirosis (optional, recommended in most areas): at 12 and 16 weeks
• Kittens
• Herpes, Calicivirus, Panleukopenia (FVRCP): every 3-4 weeks, from 6-16 weeks old
• Rabies: once at 12-16 weeks
• Feline Leukemia (FeLV) (optional, recommended for kittens): at 8 and 12 weeks
• Adult Dogs & Cats with initial and regular vaccination history
• DAP or FVRCP: every three years
• Rabies: every three years (some states/municipalities require annual vaccination, however)
• Bordetella and leptospirosis (dogs), FeLV (cats): Annual if indicated

Why Are Puppies and Kittens Different?

Right after birth some "magic" happens inside mom and her kids - and by magic, I mean really complicated physiological changes. These allow antibodies (proteins that help prevent infection) from the mother to exuded in her milk, and for a brief period the pups or kittens can absorb these antibodies through the gut and into the bloodstream. These maternal antibodies hang around for the first six weeks or so and protect them from common diseases - that's why we generally wait until after six weeks to begin vaccinations.

Eventually those maternal antibodies start to break down, however, leaving the kids increasingly susceptible to disease. So, we start vaccinating them to teach their own  immune system how to protect itself. There's a hitch, though: the remaining maternal antibodies interfere with those vaccines and prevent the pet from developing a full immune response until they are gone. Somewhere around 12-14 weeks the maternal antibodies should have entirely disappeared, and that's why we booster most vaccines every 3-4 weeks until then - each vaccine gives the immune system a boost that keeps the pet safe, but that boost doesn't "stick" until mom's antibodies get out of the way. It's also why we don't give rabies vaccines until after 12 weeks.

Why Do Some Vaccines Need A Second "Booster?"
Some vaccines are more effective at stimulating the immune system than others; for example, a single dose of rabies will typically provide immunity for at least a year. Others, like leptospirosis, pack less of a punch; for those the first shot "warms up" the immune system so it's ready to mount a full response when boosted 3-4 weeks later. The reasons for this mostly have to do with the type of vaccine in question (see the previous article) and are beyond the scope of this article - trust your vet to sort this out for you, or ask them for the details when you've had six or more cups of coffee.

Wait, I Thought Fluffy Needed Shots Every Year?
How long is a vaccine good for? It's an easy enough question to answer - if you're willing to spend the money and time to vaccinate a bunch of animals, then maintain them in a controlled environment monitoring their immune response. The vaccine companies did this, of course, but generally just for a year. So, we knew the vaccines were good for at least that long but really didn't know when immunity started to fade, and thus when a booster vaccine was really necessary. At the time, recommending annual boosters made perfect sense as the safest thing for pets.

We now know, however, that most of the "core" vaccines generally provide good immunity for three years or longer, and most of us have changed our recommendations to reflect that. So, why so some veterinarians still hang on to the old annual recommendations? Maybe you're tempted to think it's about money - that vets see yearly dollar signs associated with yearly vaccines. That couldn't be further from the truth - after all, if money was our focus we'd all have become human physicians instead, doing essentially the same work on a different animal for three times the income. No, the reason many vets still recommend annual vaccinations is because it's a reliable way to get you to bring your pet to the clinic for the most important part of the annual visit - the physical exam.

This bladder stone - which basically filled the entire
bladder - was discovered on "routine" physical exam.
The owners had no idea the dog was having urinary issues.

It's no secret most people associate going to the vet with "getting muffy's shots," not "getting a physical." And yeah, you likely don't take yourself in for a physical yearly, either. The trouble is you know when your tooth hurts, when you've been nauseous for a month, or when your knees are starting to feel sore in the morning. You can get in the car and head to the doc as needed, or at least tell someone what's wrong and ask for a ride. Our pets don't have that luxury. Sure, sometimes it's obvious Muffy isn't feeling well - but ask yourself, do your friends and family notice every time you're not feeling well? And how long does it take them if they do notice. I couldn't tell you how often I find problems a pets' people had no idea about - everything from bum knees and ear infections, to bladder stones and broken teeth. Regular physical exams are hands-down the most essential service your vet offers, and while I don't agree with recommending vaccination more frequently than necessary to get pets in the door for that exam, I certainly understand why some vets still do it.

Note that several vaccines - leptospirosis, feline leukemia, bordetella, and lyme to name a few - don't last as long and really do need annual boosters. And for any vaccine, I always recommend a booster at one year the first time a pet receives it, regardless of the potential duration. Better safe than sorry (or stuck in the ICU with parvo). Our final article will cover adverse vaccine reactions; these are understandably a major concern of many folks, but fortunately are fairly rare.

Pet Vaccines 103 - How Vaccines Do (And Don't) Work

So, we've talked about the diseases we commonly vaccinate for in the first (canine) and second (feline) articles. Now we'll offer up some answers for the questions we commonly field about vaccines.

How do vaccines protect my pet from disease?

That's a deceptively simple question, considering how complicated Muffy's immune system is. The basic idea is easy enough to grasp, however. In order for your immune system to fight off an invading disease, it first needs to identify it. In the cellular soup that is the living body, when something new and harmful comes along it can take some time to identify it - time you often don't have when under attack by disease. Remember how much of the town got wiped out in Invasion of the Body Snatchers before folks figured out how to tell who's who? So, vaccines contain bits of the offending virus or bacteria that have been rendered harmless, giving your immune system a "heads up" on what to look for if infected in the future. That means they can take care of the enemy before it becomes a problem, instead of wasting time trying to figure out who the enemy is.

What's actually in those vaccines?

There are three basic types of vaccines. 

• Killed vaccines are basically busted-up bits of a virus or bacteria. They contain important proteins your immune system can recognize and learn to differentiate in the future, but everything's dead so the virus or bacteria can't spread or cause disease. 
• Modified live vaccines actually can multiply in the body, but they've been altered by the kids in the lab so they no longer cause disease. These generally produce much better immunity since your immune system gets exposed to a lot more virus. 
• Recombinant vaccines take the best of both worlds - generally, a harmless virus (yup, probably the majority of viruses out there cause no real harm) is injected with a few genes that allow it to produce a few proteins that are specific to the disease we want to vaccinate against. It's sort of like a good samaritan going door-to-door with photos of annoying door-to-door salesmen so you know when not to open the door.

Are vaccines 100% effective?

Realistically, nothing is 100%, but most manufactures claim efficacy of 100% or at least the upper 90's for the "core" vaccines. Non-core vaccines like leptospirosis, FeLV, and FIV sport lower numbers but are generally still pretty good - in the case of lepto, sometimes even if disease isn't prevented, a reduction in severity could be life saving. 

It's also worth noting that a very small percentage of animals will be "non-responders" to a particular vaccine - for whatever reason, there immune system won't recognize and mount a response. Another potential reason for failure is mishandling of the vaccines, which generally are sensitive to temperature - this is the main reason buying and giving vaccines yourself is a bad idea. I threw out $800 worth of vaccines a few months back when a refrigerator died over the weekend - I frankly don't trust the kid at the feed store or the businessman running a mail-order outfit to do that.

What's "herd immunity?"

Okay, so no one's ever actually asked me about the concept of herd immunity. But it's worth bringing up here. Basically, the idea is that if you create immunity to a disease in a majority of a population through vaccination, the individuals who don't develop immunity (from failure or lack of vaccination) get a sort of second-hand protection, since you've drastically decreased the odds of them being exposed to the disease. Imagine 100 people in an office. If 90 of them get flu shots, you've just reduced the risk of exposure to the flu at the office by 90% for the other 10 folks. So, even if a vaccine isn't 100% effective for everyone, if everyone gets it they'll be well protected regardless (and that's how you end smallpox, kids). 

As an aside, this is why I tend to think of vaccination (both animal and human) as a social responsibility - those 10 folks who didn't get the flu shot are not only freeloading on everyone else's vaccines, but they're serving as a potential reservoir for the disease, too.

So, two big questions remain - how frequently should pets be vaccinated, and what are the risks of vaccinating (hint: they're a lot less than not vaccinating). We'll get to them next, but for now I'll let "herd" immunity serve as an excuse to leave you with the following video.

Pet Vaccines 102 - Common Feline Vaccines

For the the first article on canine vaccines, and a discussion of rabies, click here.

Cats are not just small dogs that will agree to relieve themselves on ground-up clay. They have their own medical (among other) quirks, their own diseases, and with the exception of rabies, their own unique vaccination needs. This article discusses those vaccines and the disease they prevent. Rabies vaccination is recommended (and legally required) for cats as well; we discussed that in the prior article on canine vaccines so I won't repeat myself here.

Feline Distemper Complex (FVRCP)
This is the standard combination vaccine for cats, along the lines of the canine "parvo combo." I'll be the first to admit all the different names and acronyms make talking about it confusing. Most vets, and their medical records, use the acronym FVRCP; I've underlined the letters that acronym comes from below in an attempt to clarify.

• Feline Viral Rhinotracheitis (Herpes) and Calicivirus: These are two separate diseases, but they are so similar in how they affect cats that we tend to lump them together. Both primarily cause transient upper respiratory symptoms - sneezing, nasal discharge, lethargy and the like (rhinotracheitis = inflammation of the nose & windpipe). Infection is permanent, and both viruses may flare up temporarily any time the animal is stressed - just like cold sores in people. Herpes commonly causes ulcers on the eyes, while calicivirus more often causes oral ulcers. Both are highly contagious between cats, so it's no surprise that many cats are infected as kittens. So why vaccinate everyone then? Well, if you don't have it you don't want it - and equally important, vaccinating everyone reduces viral spread through the population in the long run.

• Panleukopenia (Feline Parvovirus or Feline Distemper): Yeah, this one has too many names. Here's the scoop - this is very closely related to canine parvovirus, and typically produces the same sort of disease - vomiting, diarrhea, etc. In kittens it also is very effective at damaging white blood cells, hence "panleukopenia," which translates to "all white cells decreased." That's important because that means their immune system is suppressed and thus they become very likely to get secondary diseases. And, in neonates, the disease may damage the nervous system, resulting in problems similar to canine distemper. So that's where all the names and confusion come from. Fortunately, a very effective vaccine comes from your veterinarian so your cats hopefully never need to worry about those details.

Non-Core Vaccines

• Feline Leukemia Virus (FeLV): This disease primarily affects white blood cells, potentially turning them cancerous (leukemia). However, the most common effect is a depression of the immune system, leading other illnesses to be more severe and predisposing to secondary infections when sick. It is transmitted via saliva, and cats are most susceptible when young. Thus, an initial series is recommended for all kittens, and adult boosters are recommended for cats that spend time outdoors - potentially exposed to other cats. Since cats may be infected for years before showing signs, testing is also recommended for all cats when young.

• Feline Immunodeficiency Virus (FIV): In many ways similar to FeLV, FIV is basically the feline equivalent of AIDS. It is capable of dramatically depressing the immune system, leading to potentially fatal opportunistic infections. The virus must enter the bloodstream directly, making bite wounds the most common manner of transmission. Vaccinated animals will test positive, meaning there's no way to differentiate vaccination from a sick animal in the future. Considering the efficacy of FIV vaccines is somewhat questionable, vaccination is recommended only on a case-by-case basis, primarily for outdoor male cats - since guys, as always, are more likely to fight. 

So there are your kitty shots in a nutshell. The next article in the series will cover questions about vaccine types, frequency, and risks. Stay tuned!

Heartworm 103 - Those Pesky Cats

Cats are not just small dogs, and feline heartworm disease is a prime example. The first two articles of this series dealt with how heartworms cause disease and preventative/diagnostic strategies primarily in relation to dogs. Today's article will outline specifically how heartworms effect cats; in many ways they are a more frustrating and elusive problem in cats, made all the more dangerous because many owners don't realize feline heartworm is a serious concern.

Accidental Guests: Heartworm Disease in Cats

Cats are not the natural host for heartworms. Unfortunately, no one seems to have explained this to the mosquitoes that spread infection or the heartworm larvae that cause it. Consequently, these uninvited and unadapted parasites really, really tick off the cats immune system. The first consequence of this is positive - cats seem much better than dogs at killing off larvae before they develop into adults. Studies suggest only about one-third to one-half of naturally infected cats develop adult worms, though it's tough to nail down accurate percentages due to the difficulties in testing that we'll go into later. 

Hey, human. Indoor cats get
heartworms too.

The second consequence of cats' super-miffed immune system is a negative one, however. Killing off the larvae within the lungs results in significant inflammation. Vessels and lung tissue gets thickened, making blood flow and air exchange less efficient and resulting in the classic signs of respiratory disease - coughing, rapid or labored breathing, and general malaise. This is now referred to as heartworm-associated respiratory disease (HARD), and it is a major reason why I've started recommending all cats receive monthly preventatives. Depending on the studies you look at, perhaps as many as 15% of cats in some areas are exposed to heartworms and thus at risk for HARD - even if they never develop adult worms. And if you think your kitty is free and clear because it's indoor only, think again - in one published series of cases, 27% were indoor-only cats.

What about the ones who do develop adult worms, though? Whereas dogs may have dozens of adults, cats rarely have more than two or three - again, their immune system is pretty good at whacking those larvae. This means many cats with adults have such a low burden they may show none of the cardiovascular problems typical in dogs. The caveat to this is that when those adults die off after a year or three, the dead worms are big enough to block off major lung vessels - and between that and the cat's once-again huge inflammatory response it can be enough to quickly kill them. Indeed, most veterinary texts list "sudden death" as a major "sign" of feline heartworm infection. That's not the way I like to diagnose things.

Diagnosing Heartworms in Cats...

...is really, really frustrating.

In the second article we talked about how the main test used to diagnose heartworm in dogs looks for a protein produced by adult female worms. This test works equally well in cats, if there is an adult female worm. In one study on naturally infected shelter cats over 50% had only a single worm, and none had more than four. This means cats are fairly likely to have male-only infections, and thus come up negative on this test - even though a single male could potentially kill them. 

Cats aren't good at tests.

Even more importantly, a lot more cats will develop the serious respiratory disease discussed above (HARD) without ever developing adult worms. On the bright side, there are antibody tests available that check for exposure to heartworm larvae. These would be great for diagnosing HARD or even male-only adult infections...except studies suggest they aren't that sensitive and miss many exposed cats, maybe more than 50% of them. 

Not surprisingly, I don't spend much time screening outwardly-healthy cats for heartworm. I'll run both tests when I suspect a cat has HARD or adult worms...but if they're negative, I don't cross heartworm off the list. Chest x-rays or ultrasound of the heart can be useful, but diagnosing feline heartworm can be elusive even when you're sure that's the problem.

Treating Feline Heartworm

Here's a quick topic. Remember how one dead adult may be enough to gunk up the lungs and cause sudden death? We can kill the worms easily enough, but we're just as likely to kill the cat. Yeah...we don't treat feline heartworm. "Treatment" is pretty much relegated to using anti-inflammatory drugs to control the signs and hoping for the best when the worms do die off. It's pretty frustrating when you find yourself crossing your fingers and wishing a freeloading parasite a long, healthy life.

Heartworm Preventatives for Cats

Most veterinarians used to be wishy-washy at best about recommending monthly preventatives for cats because adult infections were relatively uncommon, and serious complications (like death) even moreso. But the respiratory complications - which can potentially be life-threatening themselves - are looking more and more common. Complicate this by the fact we don't have a great diagnostic method  (meaning we likely are underestimating prevalence) and hopefully you're starting to understand why I've started recommending all cats stay on a monthly preventative. 

As of this writing, there are two topical products and two oral products on the market, and all are effective for heartworm prevention. Both topicals are great products, covering fleas and some common intestinal parasites while sparing you the adventure of trying to get a pill into a cat. Neither oral product covers fleas, but Interceptor covers several of the more common intestinal parasites. It's a good alternative in areas where fleas aren't a concern as it's a fair bit cheaper than the topicals.

I've covered a lot of ground in these three articles, and in a good bit of depth. If you're not 100% convinced that heartworm is a serious risk that warrants monthly preventatives, I'm happy to address any lingering questions or concerns in the comments section below!

Four Good Habits for Your New Pet

This time of year we start seeing a lot more new pets at the clinic, and we spend a lot of time talking about "to-do" and "don't-do." Many of the most common problems I deal with in older pets - behavior issues, dental disease, and obesity - may never develop into issues in the first place if good habits are established right off. So, with that in mind here are four good habits I recommend to every pet owner.

1. Make Them Work for Treats

Food rewards can be extremely effective at teaching your pet new behaviors. They can also be extremely effective at making your pet fat. Too often we get in the habit of giving a favorite treat on a regular basis not as a reward, but as an expression of affection toward our pets. Food is not love, folks. When you just want to show your pet some affection, grab their favorite toy or offer up a good belly rub. Start the habit now of only giving treats as a reward for a requested behavior or during training sessions, and only giving treats in moderation. This will make training much more effective and the resulting behaviors that much more reliable, as they aren't over-satiated with treats and they know the only way to get those tasty morsels is to work for them.

2. Brush Their Teeth

Heavy calculus and inflammed gums

Imagine that your significant other never brushed their teeth. Yuck.

I see about a patient a day with severe dental disease - we're talking rotten teeth trying desperately to get out of an animal's head. While it can sometimes be difficult to get adult pets on board with toothbrushing, almost any pet will learn to tolerate and even enjoy it if you're persistent (even cats). All that gunk that builds up on your pet's teeth is actually mineralized bacteria. Not only does it irritate the gums, leading to periodontal disease and tooth loss, it also serves as a source of infection that can spread to other organs like the heart. Every animal will need professional cleaning (just like us) at your vet a few times over the course of their lives, but daily toothbrushing has been shown to reduce how often it is necessary. So, if you get in the habit of daily toothbrushing now you will improve your pet's long term health, as well as reduce the need for cleaning under anesthesia, saving your pet some risk and yourself some cash.

3. Feed Individual Meals

I would be so fat if I lived at a buffet. While the occasional dog or cat will have the willpower to restrain themselves and stay slim with free-access feeding, those guys are by far the minority in my experience.

Feeding multiple small, measured meals is the only way to control your pet's food intake. Get in the habit now and you'll likely keep your pet from ever getting fat, and if they should start gaining weight (metabolism and activity level can change, after all) it's easy to cut back the food a bit before things get out of hand. Plus, life will be much easier if you have multiple pets and one should need a special diet at some point - say a limited ingredient diet for food allergies or a senior diet for an older pet. On that note, when you begin feeding meals the food should only be offered for a few minutes and then taken away, eaten or not. After a couple weeks they'll learn to wolf it down when offered, and you shouldn't have to worry much about Muffy finishing Spot's leftovers.

4. Experience!

Morgan digs people.

Earlier this week we had a 110lb, goofy, outgoing Mountain Dog in the clinic. I went to get him out of his run for treatment, and he balked, cowering back in the corner and refusing to come out. A pink plastic disk had fallen in the floor in front of the run, and who knows why, but he was terrified of it.

During the first few months of a puppy or kitten's life they go through critical phases where they learn what's "normal" - what the world is like, and that they don't have to be afraid of it. Exposing your pet to new experiences - places, things, animals, and most importantly people - will help them turn out happy and well-adjusted. Make a habit of seeking out new experiences with your pet and making them positive. For example, carry some treats with you when you go for a walk or to the dog park, and ask people to have them sit (work) and give them a treat. And while the early months are an important, special time, this is a habit you should keep up - you can still wind up with a pet that is afraid of everything and everyone if you later turn them into a shut-in, who never interacts with anyone but you. And be honest, you're going to feel pretty silly if your big, manly dog is terrified of a pink plastic disk.