What? Is It Time For My Horses's Shots Again, Already?

Written By Walt Friedrich

Well, maybe, but let me pose a few questions first:

Other than for Tetanus, when was the last time you had a vaccination?

Do you consider your immune system to be reasonably strong?

When you’re in the midst of a crowd, do you ever feel unsafe because there may be people nearby who have a contagious disease?

Now, ask yourself the same questions with respect to your horse.

Interesting, isn’t it? If you’re like most folks, you haven’t been vaccinated since you were a child (except maybe for Tetanus, if you cut yourself in the barn recently). And yet, you’re not worried about being near sick people in a crowd. If you give it some thought, would you come to the conclusion that you’re still protected from those illnesses because of all those childhood injections you endured, and your immune system is strong? It’s a logical explanation – we know contagious diseases can spread easily (evidenced, for example, by shocking conditions in some third-world countries), yet you – and most everyone you know – are spared. Well, feel good about it. You should. In large part, it’s because of those childhood injections – even though they took place many years ago!

S0 now consider the contrast between your situation and your horse’s: if you’re like most horsepeople, your horse is younger than you are – and yet your horse may have received “shots” regularly, perhaps every year, while you received them only ONCE, long ago. His kind has been around at least as long as ours, and, like us, he’s survived pretty well – and, also like you and me, without benefit of all those injections during most of those millennia, thanks to our good, strong immune systems! See the dichotomy?

The typical domestic horse is the subject of repeat inoculations every year or two, and always against the same threats! How strange. As history has amply demonstrated, his immune system is quite adequate, and for all but the current miniscule percentage of his species’ total history he received no injected protection, but now he’s apparently considered to have such a weak immune system that it needs frequent reinforcement inoculation.

The pharmaceutical companies that formulate the injectibles tell you, virtually in unison, that it is simply not safe to take your horse to a horse show and risk exposing him to other horses, or that there is imminent danger that a bug may bite your horse and infect him with some horrible virus, and therefore your horse should be vaccinated again...never mind that he was just boostered last year. Yet you, without a booster, are at the same horse show, even though you are just as much at risk as is your horse. Why are you not pressured to receive the same injectable precaution?

Which leads to the obvious question: could it be that yearly vaccinations for our horses are unnecessary? Over the years your horse has very likely been vaccinated for the same diseases repeatedly, and to some of them he has developed immunity. Yet powerful stuff is pumped into his system with every booster shot -- could the practice of over-vaccinating our horses actually be causing him harm?

No-one is claiming that horses should never be vaccinated, but rather that over-vaccination is a problem. Make note, however, that some changes have actually been made in some parts of the world: there is often a longer time interval between tetanus vaccinations than there is with most vaccines, for example. Perhaps we should be traveling farther down this path.

Let us pause for a moment and consider that much that you have just read might be called the contrarian viewpoint. It’s logical, we need to give it that, but it’s also pretty strong. But now let’s have a look at the other side of the story.

A newborn foal is very well-armed as he enters life, provided he receives his mother’s colostrum as he suckles. His natural protection is quite limited, but the colostrum contains his mother’s full repertoire of antibodies. A great way to start life, better even than your and my childhood vaccinations.

When he’s six months old, or thereabouts, his inherited immunity has declined somewhat, but he has also begun to develop his own immune system inventory of protection, adding to what’s still there from his mother. He should now bolster his colostrum-provided protection  by getting his first array of shots -- the equine version of our childhood inoculations.

So far so good, he’s ready to face the world. But it’s the adult world, now, and he faces adult horse situations. Since the purpose of vaccinating is to stimulate the immune system to create protective antibodies, his new arsenal will protect him from future attacks. But some of these menacing microbes are great at evasion – they mutate, with the result that the stock of antibodies in the bloodstream and cell walls may not work on an attack by a mutation, and he can suddenly be in trouble. Further, the lifetimes of different antibodies are not all equal, some quite short, in fact. Consider the common cold in you and me – one cold is never enough, it seems, because we continue to “catch” them throughout our own lives. Either the antibodies we’ve built up are short-lived, or maybe what we “catch” is a mutation that’s changed enough that our antibodies may not recognize it. The same considerations apply to our horse. Pharmaceutical companies that develop the injectibles need to be constantly alert for new strains, and must develop new vaccines to counter them. It is a long-term, continuous effort, a sort-of early-warning system, to track tomorrow’s potential invaders.

Of course the vaccine manufacturers are in business for profit, and if their products do not do the job, then veterinarians will not use them and horse owners will not buy them.  If a vaccine does not do its job well, it will not last long on the market.  On the other hand, manufacturers must act conservatively and make realistic evaluations of their products. They would be out on a legal limb if they claim more than a product can deliver.  Thus, it seems safe to assume that the effects of a vaccine will last longer than the suggested time between booster shots. Updates are needed by the immune system so that its protective inventory is always up-to-date and prepared; it gets updated every time the horse is in contact with an infecting agent as well as every time he gets booster shots. A pretty good protection scheme, that – but the manufacturer must make sure his updated vaccine is available and delivered before it’s obsoleted by further mutation. Immunology is a pretty complicated science, wouldn’t you say?

So we can see why manufacturers “push” repeated shots – often, today’s formula is updated from that of an earlier version, and while he certainly is in business for profit, the manufacturer is also in business to keep our horses healthy – and so are our veterinarians. It’s obvious that veterinarians in general are very honest in not providing any products to horse owners that do not bring good value for their cost. Most believe in an item completely or they will not provide it to a client or patient. Certainly, there are exceptions to that observation, but in general, our veterinarians take pains to provide an extra level of service to us and to our horses, and in so doing, many will join the manufacturers in “pushing” regular boosters.  

Well, there you have it. A dichotomy. On one hand it seems to appear that we’re over-vaccinating, at significant cost to ourselves and possible harm to our beloved horses. But on the other hand, pharmaceutical manufacturers and veterinarians need to be sure that they are providing more than just adequate care, and doing so in a timely fashion.

It is a dilemma. We can second-guess them all day long, but who among us would risk arbitrarily tweaking the rules of the game, so to speak, when the stakes are so high? The take-home is that it is probably wise to provide booster shots to our healthy horses in order to keep them that way, but do the difficult research to determine how often your horse gets vaccinated and against what dangers. They should not be a cookie-cutter answers, like “annually” and “for everything”, but rather customized for your own horse’s circumstances. Remember, we are the ultimate decision-makers. If we think that giving yearly shots is too often, it’s easy to schedule them only every two years – or every three – or however frequently we deem is enough. Considering all the unknowns, one action seems to make good sense – discuss your specific situation in detail with your vet. There is a large fund of knowledge in every vet – we should all partake of it, and our horses are the beneficiaries.

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