Rabies: Flushing viruses out of the forest

Like any curious pup, the second Arnie encounters hedging/bushes/shrubbery, his first instinct is to dive right in in the hopes of flushing out some yummy yummy bunnies/kittens/boars.

Like any over-protective owner, I run after him screaming “GET OUTTA THERE YER GUNNA GET BITTEN BY A SNAKE!!!”

Cause when you start poking your nose in places you arent supposed to be– you dont always find yummy squirrels. Sometimes you flush out bad things… like rabies infected vampire bats. Thats exactly what logging/mining expeditions in Venezuela have done. Theyve displaced colonies of vampire bats… vampire bats infected with rabies… vampire bats that are now biting humans. Thus in the past year, 38 Warao Indians have died from rabies, half of those within the past couple of months, as youve probably read in the news.

Most people know a little bit about rabies because of Old Yeller, and the fact we have to vaccinate our pets against it (its the law).

Im going to write a bit about the viral life cycle so certain persons currently traveling in South America will know what to do if they suspect they have been bitten by a vampire bat ;)


If you get bitten by a wild mammal (rabies can only infect mammals), assume that it is rabid. You cant afford to ‘wait and see’, because after rabies infection gets to the point where you are showing symptoms, its in your brain, and its too late to treat. But while it can take a long time (few days to a few months) after a bite to get ‘rabies’, its not because rabies goes ‘latent’. The silent period is just a side effect of rabies life-cycle, and it just so happens thats what makes rabies treatable.

  1. Infected animal carries rabies viruses in its saliva. It bites you on, say, the leg. Viruses enter your leg muscle cells and replicate. The viruses move into the sensory nerves in your leg (the nerves that say ‘OMFG I JUST GOT BITTEN BY A RABID ANIMAL OOOOOOWWWW’)
  2. The viruses move to your legs dorsal ganglia and replicate some more
  3. Viruses get into your spinal cord, use it as a highway to your brain
  4. Viruses infect your brain stem and cerebellum, and takes over your behaviors
  5. Virus spreads to your eyes, nose, and most importantly, salivary glands
  6. Youre crazy and can go bite someone else and infect them

We figured out you could stop rabies through animal experimentation way back in 1887– If you infected a rat in the foot, then cut its sciatic nerve, rabies infection never progressed and the mouse didnt die. They also figured out that you could wait a few days, up to three weeks, before severing the nerve, and the animal would still survive. So, if you can clear the viral infection before it travels to the spinal cord, you prevent it from infecting the brain, thus prevent the viral encephalitis that ultimately kills someone with ‘rabies’.

So, if you get bitten by an mammal, the first thing they do is give you a rabies vaccine. Youll get four more over the next few weeks to really piss your immune system off, kicking it into high-gear so it can (hopefully) overtake the infection. Lots of B-cells pumping out antibodies, lots of cytotoxic T-cells honed-in on killing rabies infected cells.

Initially, you also get a dose of anti-rabies antibodies to tide you over until your own immune system reacts to the vaccine and can take over (its not a good long-term treatment due to serum sickness, and your own immune system will take over just fine, unless youre immuno-compromised).

If you get treated early, rabies isnt a death sentence. And, in Venezuela they are starting to vaccinate at-risk humans, distributing mosquito nets to keep vampire bats away from sleeping people, and deploying med-boats to remote areas. So this recent rabies outbreak is unfortunate, but controllable.

But the next virus we flush out of the forest… what if its not ‘just rabies’…?

Comments

  1. #1 Sili
    August 11, 2008

    I did not know any of that (almost). Hadn’t heard of the indians, and I didn’t know that was why Old Yeller was shot(OY is one of those things I know of, but haven’t seen, because of the way it permeates all of US culture – like The Princess Bride).

    Completely off-topic, but it looks like someone snuck out the security footage after Bossman’s latest little peptalk to your lab.

  2. #2 Becca
    August 11, 2008

    If you infected a rat in the foot, then cut its sciatic nerve, rabies infection never progressed and the mouse didnt die. They also figured out that you could wait a few days, up to three weeks, before severing the nerve, and the animal would still survive.
    Kinda makes you wonder how they figured that one out…

  3. #3 dNorrisM
    August 11, 2008

    Old Yeller had rabies?? Mom told me she had babies!

    (“Joke” stolen from Friends)

  4. #4 Paul Lundgren
    August 11, 2008

    Don’t you think it’s just a matter of time before it happens? These viruses are getting more “competitive” all the time, with the diminishing habitat, and we’re gonna pick them up somehow.

  5. #5 efrique
    August 11, 2008

    We figured out you could stop rabies through animal experimentation way back in 1887– If you infected a rat in the foot, then cut its sciatic nerve, rabies infection never progressed and the mouse didnt die.

    First thing is how cool it is that they figured out that cutting the nerve worked to stop rabies.

    Second cool thing is it makes you change from a rat to a mouse!

    If you give the mouse some of the anti-rabies antibodies, does it turn back into the rat you started with?

    If you get treated early, rabies isnt a death sentence.

    Yeah, but now you’re a mouse, and that’s no picnic.

  6. #6 Bayesian Bouffant, FCD
    August 11, 2008

    If you infected a rat in the foot, then cut its sciatic nerve, rabies infection never progressed and the mouse didnt die.

    A nasty virus indeed; first it changes your species, and then it kills you.

  7. #7 Screechy Monkey
    August 11, 2008

    The law requires people to vaccinate their dogs? That explains all the autistic dogs….

  8. #8 The Chemist
    August 11, 2008

    I’m not sure, but I hear you should also worry about large snake bites (the fact that it is only carried by mammals is not lost on me, bear with me a moment)

    I was watching one of those true stories on the Discovery channel where one of those herpaphiliac freaks who keep large constrictors in their homes talks about getting attacked (big surprise). I can’t quote him verbatim but what he said goes something like this:

    “I was in the emergency room, and they were giving me these rabies shots in the stomach and I’m yelling at the nurse, ‘It’s a REPTILE it doesn’t get rabies!’ and she was yelling back at me, ‘YES! But its food DOES!’”

    Maybe it was just the hospital being overcautious, but it seems plausible.

  9. #9 scott fanetti
    August 11, 2008

    ERV:

    You talk alot about having really tight control of the little snips of rna and dna you work with. Is the technology currently at a point where one could just write a virus and plug the code into some host cells to compile it? If that is the case, can you give a cell infected with a virus a piece of bad code to introduce a bug into the virus replication?

    It is truly incredible that we are alive in a time where we can consider the basic fundamental elements of life for what they truly are. Code.

    I just hope I live long enough to see people able to reverse engineer the whole system and see it from a programmers perspecitve.

  10. #10 Jared
    August 11, 2008

    Scott, even if you were to introduce a “bug” into the viral code, you lower the odds of that virus surviving. When you do that, your buggy bug doesn’t out compete any other strains and fades into oblivion.

    By the way, for all you computer programmers out there:
    for fun, have a crack at the biological operating system;
    consider coding that’s in quaternary. That code can be used on its own as machine code (ribozymes) or to encode for hardware production (proteins) or for software commands (activators, enhancers, deactivators, etc.). Signals for input can be analog, digital, or both and output can also be any combination of analog or digital. Signals can modify hardware (protein modification), or alter the software (modification of DNA), or modify the system (cell) in multiple ways. I could go on at length, but I would encourage all you E-squares out there to have some fun with biology.

    FYI: I started out in computers as a kid, loved programing, and got into genetics in collge. There’s a little of my bio you can’t get anywhere else…

  11. #11 Scott Fanetti
    August 12, 2008

    Yes – I guess I did not consider the fact that the virii that were disabled would not proliferate within the population. I guess fighting a virus is kind of like fighting evolution. The better your strategy to kill a negative vecotr, the higher the chance a survivor will come and proliferate in the population.

  12. #12 ERV
    August 12, 2008

    Scott– You arent totally off base, though!! The trick is to manipulate the virus in such a way it doesnt effect the overall fitness of the virus, like what some folks at the Pasteur Institute are trying to do with Polio!

    Hack the planet!

  13. #13 Lab Rat
    August 13, 2008

    ooh nice post. As someone with a vested interest in viruses it’s great to find out more information about different types (especially from ERV who I almost worship). One question though, do you know if Rabies are lytic or lysogenic phages? I’m guessing that they’re lytic, as the response is so quick…

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