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Coming in 2014 to a Vet Near You: Tail Vaccinations

Vaccine injections have been linked to aggressive sarcomas in cats, leading to horrible limb amputations. That could end soon.

 |  Jan 14th 2014  |   4 Contributions


Sometimes when I am feeling philosophical I muse about the greatest advances in the history of medicine. I realize such musings are not mainstream, but it should come as no surprise that I have a special interest in medicine.

There have of course been many great advances in the history of both human and veterinary medicine (and the two very closely parallel each other). The germ theory of disease and subsequent understanding of the importance of hygiene certainly ranks highly among medicine's greatest steps forward. So do the invention of antibiotics, intravenous fluids, anesthesia, pain killers, and diagnostic imaging (technologies such as radiographs, MRI, and ultrasound).

But in terms of sheer quantity of lives saved (be they human or animal), suffering prevented, cost effectiveness, and elegance of theory, one advancement stands head and shoulders above all others: vaccines. Vaccines reliably protect against some of the most dreaded diseases out there. Smallpox, polio, canine parvovirus, feline panleukopenia, and even rabies can all reliably be prevented with vaccines.

Vaccines have been around for quite a while, and since about a day after their invention there have been vocal anti-vaccine activists. Whether they fret that vaccines are unnatural, or cause autism (they don't), or are against their religious tenets, the vaccine haters have been around for as long as vaccines. Frankly put, when discussing vaccines in humans, dogs, and most other species -- except cats -- the anti-vaccine activists don't have a logical leg to stand on. The benefits of vaccines, particularly in juveniles, so incredibly outweigh the disadvantages that it's generally blindingly obvious.

Photo of Dr. Eric Barchas by Liz Acosta

But then there are cats. You already knew that cats are unique creatures. But feline exceptionalism isn't merely a political statement or a frame of mind. It's a fact of science. Cats' bodies are like no others.

Now, in general, the benefits of vaccines in cats still very decisively outweigh the risks -- up to a point. Unvaccinated cats die horrible deaths from panleukopenia or feline leukemia at appalling rates. But feline vaccination is not completely without risk. Vaccines in cats have been linked to cancers.

Originally called vaccine-induced fibrosarcomas and then later vaccine-associated sarcomas, these cancers were first noticed to develop at the site of vaccination in cats. Initially the rabies and leukemia vaccines were fingered as the only culprits. However, it has now become clear that any injection has the potential to trigger cancers in cats (although the rabies and leukemia vaccines still appear most likely to cause them). The name has subsequently been changed to injection site sarcomas.

Injection site sarcomas are malignant, aggressive cancers. Their exact cause remains a mystery, but inflammation appears to play a role in their development. Cats' unique inflammatory processes appear to put them at greater risk of injection site sarcomas than other species (although the phenomenon has been noted as a rarity in many species).

Vet immunizing a cat by Shutterstock.

The cancers develop at the site of the injection. Back in the olden days, vets gave cats all their vaccines in the scruff of the neck. There was a good reason for this: The scruff of the neck is by far the easiest place to administer a vaccine. However, injection site sarcomas that develop in the scruff of the neck are nearly impossible to remove.

So, a gory solution emerged. Guidelines were issued that advised veterinarians to vaccinate cats in the legs, below the elbow or the knee. Sarcomas that developed in these locations could more readily be removed -- by amputating the affected leg.

Now, if you think amputating a leg is a less than perfect way of dealing with this problem, you're not alone. But it seemed to be the best -- or rather the least bad -- option available while the whole mess of injection site sarcomas was being sorted out. In the end, the only acceptable solution to the injection site sarcoma issue will be vaccines and protocols that lead to adequate protection against disease with virtually no risk of sarcoma development. Unfortunately such a solution seems quite a long way off.

And if amputating a cat's limb to treat a cancer caused by a vaccine were not already unpalatable enough, there is another problem. It is evident that many vets are not following the guidelines. There are regular reports of sarcomas above the elbow or knee, in the scruff, or even on cats' flanks (it seems that some vets aim for the upper rear leg -- which is wrong to begin with -- and miss the leg altogether). These sarcomas are virtually impossible to cure.

The tail: expendable ... relatively? A cat rubs a fence with his flanks and tail by Shutterstock

Now, however, a potentially even less bad (although still not good) vaccination guideline may be about to emerge: tail vaccination.

A recent paper published in the Journal of Feline Medicine and Surgery discussed a pilot study of tail vaccination in cats. The paper compared cats who were vaccinated according to current guidelines (in the legs below the elbow or knee) with others vaccinated in the "distal tail" (which means the end of the tail). Tail vaccination appeared to be comparable in efficacy and, somewhat surprisingly, in ease of administration. The authors report that tail vaccination was well tolerated by the cats in the study.

Amputating the tail, or a portion of the tail, is a far-from-perfect way of dealing with sarcomas. But it's a far sight better than amputating a leg. It's also hard to imagine even the most absentminded of vets aiming for the tail and hitting the flank.

I sincerely hope that a real solution to injection site sarcomas will be forthcoming in the near future. Unfortunately, the prospects for such progress don't seem terribly good at this time. Some of the best minds in veterinary medicine have been working on the problem for decades and, pathetically, tail vaccination is the most promising practical development I've seen in a while. Let's hope the pace of progress truly picks up.

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