Rabies: what is it and why do we vaccinate?

Written on September 28, 2017 by Krista Vernaleken, VMD Hospital: Bulger Veterinary Hospital

Imagine a disease that could affect anyone, young or old, and can affect any mammal.

The animal is bitten, then seems OK for a while. A few weeks pass and he or she starts to act funny, maybe a little listless, maybe kind of irrationally angry and aggressive.  You go near it and it bites you…then the same happens to you!  Sounds like something from a zombie movie, right? shutterstock_76201372

That disease is Rabies, and while nobody rises from the dead (as far as we know), symptoms of rabies look and sound like the early scenes in zombie apocalypse movies.

Most pet owners think of rabies in passing. “Rabies: sounds bad.  Better get my pet her shot.” And most of the time, that may be enough: it’s very bad and vaccines can prevent it.  Maybe the disease conjures up images of “Old Yeller,” and “Kujo” if you are of a generation that has seen these classic movies.  Maybe somewhere you heard that Edgar Allen Poe might have died of Rabies (one of many theories of his death).

Most pet-owners are aware that the vaccine is required by law and that it is a disease that is communicable between animals and humans.

Indeed, these things are true.  But what is Rabies really, and how likely is it that you will come into contact with an animal that has rabies?

What is Rabies?

Rabies is a viral disease.  Unlike most viral diseases, which are highly species-specific and can only really affect one species, rabies can infect all mammals.

The disease is transmitted when a healthy animal is bitten by a rabid animal. Viral particles are present in the saliva of the rabid animal which are passed into the blood stream of the healthy animal.  Viral particles replicate in the healthy animal and migrate up the nerves and into the central nervous system, then out into the salivary glands.  At this point, the new animal is capable of transmitting the disease.  The time between being bitten and being capable of transmitting the disease is highly variable – usually this is 2-8 weeks, but there have been cases where it has been both shorter and longer.

A pet or human is considered potentially exposed to rabies when bitten or scratched by any animal (wild or domestic), whether vaccinated or unvaccinated.  This is a tricky thing to understand, because it seemingly makes no sense – why is it considered rabies exposure if a vaccinated dog bites another vaccinated dog?  Because rabies is so very serious and fatal to any mammal that it infects that we can’t afford to take ANY exposure lightly. No vaccination is 100% – so if a vaccine failure occurred there could still be a risk.

To flip this on its head, what if we weren’t strict about it?  What if the vaccine your pet received was a dud (or your pet was never vaccinated).  Not likely, but what if?  And then your dog goes out and eats a raccoon carcass he or she finds (don’t get me started on the crazy stuff well-fed dogs will eat!).  But because in our imaginary world laws about this aren’t strict, no one does anything.  Everyone goes about their lives.  But 2 months later, your dog starts acting strangely.  It gets worse, but rabies isn’t on their list because the signs aren’t classic and rabies is rare.  You euthanize your dog, never knowing it had rabies.  You and your family were exposed, but didn’t even realize it.  Your entire family could die of this, only realizing too late that earlier recognition would have saved all of you.  This is a dire and extremely unlikely scenario, but this is why we are so strict about it.

Rabies Protocols and Guidelines

There are set protocols in place in Massachusetts which provide vets and animal control officers with clear guidelines.  Here are some examples where humans or animals should be concerned about rabies exposure:

  • Obviously, if a human or domestic animal comes into any direct contact with a known rabid animal, the human or pet should be treated.  For humans, see your local ER.  For animals, the treatment and quarantine period depends upon whether the pet is currently vaccinated.  But it has to be done quickly – within 10 days of the exposure.
  • There’s a known rabid animal, your pet was in the yard with it, but you’re not sure if they were in contact or not.  This is still considered a rabies risk and your pet should be treated proactively.  Again, the treatment depends upon your pet’s rabies vaccine status.
  • Your dog meets and greets a raccoon in the yard.  You’re not sure where the raccoon is now, but there’s blood on your dog.  This is considered exposure to a “suspect rabid” or “possibly rabid” animal.  Since we don’t know for sure, we assume it could have rabies and treat accordingly.
  • Your dog is out on a casual walk, and gets into a fight with a neighbor’s dog.  Even if both are up-to-date on their vaccines, this must be reported so that the biter can be monitored appropriately.
  • You find a bat in the house.  Especially if you have kids.  Please note that many incidents of human rabies occur when bats bite sleeping humans.  The humans don’t know – in fact kids sleep so soundly that they might not notice they were bitten.  Any bat found in a home should be considered a rabies risk and tested – usually your local animal control will help you catch the bat or provide advice. Yes, the bat will need to be euthanized and tested. I like bats and think they are hugely helpful in the environment.  But what if the reason it is in your house is because it’s rabid?  Are you willing to bet your family’s life that it isn’t rabid? It’s unfortunate, but rabies is a serious disease that is fatal to all mammals. It warrants being taken extremely seriously.

These are just some of the situations that owners might not think they should be concerned about.


Vaccination in pets (and humans when warranted) is considered highly effective.  Due to the severity of the disease, it is still treated very cautiously when there is a possible exposure.  But there haven’t been many cases of definitive rabies vaccine failure.  Your best insurance is to keep your pet vaccinated.

The law requires that all unvaccinated pets brought into a veterinary hospital be vaccinated.  That means that technically, if you bring your pet to me and it is unvaccinated or has an expired vaccine and is healthy enough to be vaccinated, I as a veterinarian MUST vaccinate.  I don’t have the right to allow you to say no.

And this applies to indoor cats and ferrets, too.  ALL mammals can get rabies.  This includes rodents and bats which may enter the home and interact with cats and ferrets.  It is true that rodents are considered excessively low risk, because they are so small that most of the time, if they were attacked by a rabid animal like a raccoon or coyote, they would be killed and therefore never able to infect another.  The state does not usually recommend testing dead mice you find in the house, unless there are extenuating circumstances.

No vaccines exist for rabbits, guinea pigs, or other pocket pets.  But if a vaccine exists (dogs, cats, ferrets, and most large animals like horses and cattle) then your pets should be vaccinated.

The ramifications of exposure to rabies are severe and fatal if untreated.


If an animal or human is exposed to rabies but is treated in a timely fashion, it is considered 100% treatable.

Treatment in animals consists usually of a booster vaccination and then some confinement or quarantine period based upon the previous vaccine status of the pet.

Treatment in humans is immunoglobulins and a series of post-exposure vaccines.  Those at high risk, like vets and spelunkers (which I mention because I love that word, and also bats live in caves) should have pre-exposure vaccines, which makes post-exposure treatment much easier.

But here is the bad part:  if not caught right after exposure and allowed to progress until signs appear, the disease is 99.9% fatal.  Completely Untreatable. There is no cure.

Each state reports their rabies cases independently.  In Massachusetts, from 1992 to 2016, approximately 10% of submitted cases have come back positive.  This dipped slightly down to about 5% (the lowest point) from 2011 – 2013.  In 2016, the most common species to be positive were raccoons, skunks, bats, cats, foxes, and woodchucks.

The good news is that cases identified in domestic animals are still quite rare, and human cases are even rarer in the US – only 1-3 cases are identified annually.  This is 3 cases too many.  And sadly, those who feel vaccinations cause grave side effects often use the rarity of the disease as a justification for not vaccinating.  The disease is rare BECAUSE we vaccinate.  Vaccination rates must continue to be high or the disease and associated deaths will increase.

Fortunately, there may be hope on the horizon. There have only ever been been a total of 3 known people who have ever been successfully treated after signs appeared.  That’s not a lot.  But 10 years ago, we would have said that there had never been a successfully treated case.  Prevention is still the best option, and this starts with awareness.


More reading:



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Massachusetts Veterinary Referral Hospital

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General Practice, Emergency & Specialty

Bulger Veterinary Hospital

North Andover, MA 01845
ER: 978.725.5544 GP: 978.682.9905