bats and rats and rabies, oh my!

Regarding http://www.straightdope.com/classics/a1_029.html:

According to the New York State Department of Health, there were 32 human rabies cases reported in the U.S. from 1990-2000. Of those cases, six were contracted abroad, and all six typed as dog rabies. Twenty-four of the 26 domestic cases typed as bat rabies. Therefore, however few bats actually have rabies, and however few humans get rabies each year, the majority of humans in the U.S. who die of rabies got it from a bat.

In most of the bat rabies cases there was no recorded exposure to bats. (Unfortunately, by the time rabies is suspected, the patient is generally no longer able to answer such questions.) The most obvious conclusion is that humans exposed to rabid bats are less likely to realize that they’ve been exposed and therefore less likely to seek prophylactic treatment than humans exposed to, say, rabid raccoons.

There is also some evidence that some strains of bat rabies – specifically the silver-haired/pipistrelle variant – are more infectious than the canine variant, hence more likely transmissible by a superficial bite or scratch that goes unnoticed.

Regarding the prevalence of rabies among bats, my vet school lecture notes claim that while <1% of randomly collected bats have rabies, up to 5% of those encountered by the public and submitted for testing are positive. (No better citation given, I’m afraid). Even granting that sick bats are easier to catch, it seems plausible that rabid bats are overrepresented among the population we encounter.

Given all of this information, it is not unreasonable to treat any physical contact with a bat as a possible rabies exposure. (My understanding is that transmission by inhalation is still under debate.) Sure, the wildlife and the unvaccinated cats and dogs are more likely to have and transmit rabies – but for whatever reason they are less likely to kill humans.

Regarding rats and rabies, we were told in the same lecture that rodents are very susceptible to rabies and therefore tend to die before they begin shedding significant amounts of virus in their saliva. So realistically, any rat healthy enough to bite probably doesn’t pose much of a rabies threat.

Judy

Basically, the reason people get rabies from bats is stupidity. Bats are, as has been stated, hard to catch, unless they are sick or injured. People with less than a full deck may see such a bat and pick it up. I do not have documentary evidence, but I would venture a guess that none of the cases of bat rabies reported in humans came from a bat on the wing.

Perhaps what we are typing as bat rabies is being incorrectly identified, and it comes from another animal, since there is no recorded exposure to bats? Or am I grasping at straws here?
keith in tampa - if we are going to blame bats, don’t forget the dreaded vampire bat. Maybe some representatives of Desmodus rotundus are flying over the border to sample some Yankee blood.

Of the 32 human rabies cases, did any of the victims survive?

Rabies is a virus that attacks brain tissue; it’s overwhelmingly fatal, but not 100% fatal. Survivors have debilitating brain damage, but some do survive.

Without vaccination or prompt treatment, rabies is pretty universally fatal. The few (six, I think) survivors all had a history of either pre- or post-exposure prophylaxis.

I used to have a copy of the Alabama state rabies manual - I can’t seem to find my copy now - that I was given in vet tech school. According to it, one reason that people often (relatively speaking) contract bat rabies is because they have no idea they have had any exposure to a bat.

Of course there are many people who don’t realize that simply picking up a bat is risky, but most people (at least in the southern US, where rabies is endemic) realize that a bite from any wild animal could possibly transmit rabies, and they immediately seek medical advice. However, rabies can also be transmitted through a scratch, mucous membranes, or an already-existing break in the skin through exposure to body fluids of an infected animal. For example, you can also catch rabies from cattle, even though they really don’t have any teeth to bite you with! You can also contract rabies by having a rabid animal drool on your fresh paper-cut. Also, most of the bats in the US are pretty small specimens with correspondingly small mouths, so a bite might not even be noticeable.

Bats sometimes enter houses, maybe by flying through an open window or doorway in pursuit of an insect. A few lucky people have had a colony of bats set up housekeeping in their attic or chimney, from whence they sometimes enter the living quarters. A person who is asleep in a room with a bat frantically seeking escape could receive several ‘exposures’ without ever waking up. They may wake up after the bat has escaped, or even wake up and find the bat in their room, and never realize they have been bitten or scratched. If you have no idea that you’ve been exposed, you are not going to have any reason to even think of rabies until you are already showing symptoms (by which time it is usually too late). As a matter of fact, I seem to recall that, in the US, rabies is usually diagnosed postmortem during autopsy because it is pretty rare in humans and most doctors never even consider the possibility. (Not that an immediate diagnosis is likely to have any effect on the outcome.)

So please don’t be so quick to call people ‘stupid’, okay?

JillGat, jmp64, and any other willing experts who happen to be reading this thread, while in vet tech school an instructor (a veterinian) mentioned two rabies cases that allegedly were contracted without direct exposure from an animal, and ever since I’ve wondered if these were true stories or if he made them up help throw a scare into us (to make sure we were very careful in our future careers).

In one case a man supposedly contracted rabies from a wood splinter. A farmer/rancher, he was diagnosed with rabies before his death - I can’t remember which animal now except that it was a raccoon, skunk, or fox - but no one could figure out how he contracted it, since there was no evidence of a bite or suspicious scratch and the man hadn’t mentioned any encounter with the identified species to his friends or family. The only ‘suspicious’ thing that could be found during autopsy was a tiny wood splinter in his arm - which they eventually tested and found positive for the virus!

The man and a neighbor frequently encountered each other while doing various chores near the fence between their properties, and would prop against a handy fence post and chat. The speculation was that the rabid animal had just begun to show symptoms so was still functioning well enough to be frightened off by the man’s approach, that for some reason it had been licking or biting the fence post, and the man had the misfortune to get a splinter from a saliva-contaminated spot only moments after the animal left.

The other case was a chimney cleaner somewhere in south Alabama (I can’t remember the name of the town, now) who apparently contracted bat rabies after cleaning a chimney where bats had been nesting. (Is nesting the correct term for bats?) Supposedly this was never positively confirmed, but the victim had recently cleaned a chimney after the owners evicted some bats that had moved in there, and there didn’t seem to be any other source for the infection. (I guess by the time he/she was diagnosed it was too late to test the chimney.)

Have any of you ever heard of these two cases? Did/could that happen? It’s a rather frightening thought for someone who lives in a rural area and has to literally chase raccoons, possums, etc. away from the cat food.

JillGat:

But it’s a virus. Aren’t there going to be statistical immunes to every virus?

Six out of the 32? Or out of another n?

The Center for Disease Control rocks my world.
http://www.cdc.gov/ncidod/dvrd/rabies/Bats_&_Rabies/bats&.htm
Unfortunately, this is the dumbed down page with no statistics. Backtrack on the URL for numbers 'n’at.

http://www.cdc.gov/ncidod/dvrd/rabies/Epidemiology/Epidemiology.htm
"Wild animals accounted for 93% of reported cases of rabies in 2000. Raccoons continued to be the most frequently reported rabid wildlife species (37.7% of all animal cases during 2000), followed by skunks (30.1%), bats (16.8%), foxes (6.1%), and other wild animals, including rodents and lagomorphs (0.7%). Reported cases in raccoons, decreased 3.2% from the totals reported in 1999. Reported cases in skunks, foxes and bats increased 7.1%, 17.9% and 25.38% respectively from the totals reported in 1999. "
They also have neat maps of the US with incidence densities. Cool stuff!

Also, check out the Kid’s Rabies Home Page!

InstantCrisis

The link to Cecil’s article didn’t work for me. I hope I’m not being repetitive.

I didn’t notice that at first. The link in the original post has been corrected.