From William R Elliott, Ph.D.: (excerpted from a
posting on CaveTex, Wednesday 21 April 1999)
I'm not an MD, but I have followed this subject of rabies in the
scientific literature for years. The risk of rabies from caving is almost zero
unless you actually handle lots and lots of bats without rabies vaccination.
Cave and bat biologists don't even do that, usually. If you are going to handle
bats, better get the human diploid rabies vaccination (maybe $100-200 cost). I
know a grad student who failed to do this, even though he was handling bats
while mist netting. He finally got bitten, and had to pay $2500 for
post-exposure rabies treatments, which was necessary.
Perhaps 20 confirmed cases of bats passing rabies to humans (who
died) were found in North America in the last few decades. See Bat Conservation
International's web site
for details. None of these cases were cavers, and none were confirmed from cave
situations. It's strange, but more than a few of these cases may have been
caused by the silver-haired bat flying around someone's house. No evidence of a
bite was found in most of those cases. This is a mystery. Most cases of human
rabies were acquired from dog bites. That's why dog catchers and mammal
biologists usually get vaccinated. In Texas skunks and foxes are a major
wildlife reservoir for rabies, which gets passed sometimes to domestic animals.
Dogs are the major reservoir. Texas raccoons rarely have rabies, while coons in
the eastern USA often have rabies. Bat populations probably have far less than a
1% rabies rate.
If you want to know more about the two people who died of bat
rabies in Texas in the 1950s, read my chapter on Conservation in the 1994 NSS
Convention Guidebook, The Caves and Karst of Texas. It gives the history
of bat protection in Texas, and some previously unpublished details about the
mining engineer and the health dept. lab worker who died of rabies. The lab
worker may have gotten infected in a cave, or in the rabies lab where he worked,
or from an experimental live rabies vaccine given to him by his own physician.
The risk of getting rabies from walking into a bat cave and just
breathing the air is probably very low for humans. A study of caged animals in
Frio Bat Cave proved that they could catch rabies by the "aerosol route",
without being bitten by a bat. But the animals were exposed for weeks in a
hostile atmosphere, which included caustic ammonia vapors that probably weakened
How effective is the Rabies vaccine at preventing Rabies?
One more thing about the rabies "vaccine" that needs clarified:
It DOES NOT prevent you from contracting rabies if you get bit
by an infected animal. It merely reduces the number of post-exposure shots you
need to three. Not only that, but various humans process the serum differently,
so that one may have a high number of antibodies present after many years, while
another may have a count next to zero after only a year. All wildlife
professionals (including those of us that regularly handle bats) should get
their titer level checked annually. This involves drawing a small blood sample,
which is sent to a lab for analysis. Even if you have received the pre-exposure
"vaccine", YOU SHOULD STILL GET THE POST-EXPOSURE
TREATMENT IF YOU COME IN CONTACT WITH A SUSPECT ANIMAL!!! Rabies is a
deadly virus, with no known cure. If you wait until symptoms start to show, it
is too late for any treatment. If in doubt, get the shots.
Realistically though, like so others have already pointed
out, your chances of contracting rabies from caving is practically nil. Unless
you regularly come in DIRECT contact with mammals (particularly dogs and cats,
but including bats to lesser degree), then don't bother with the "vaccine". It's
not a catchall prophylaxis, and is unnecessary for general caving.
by Alicia Wisener Gale
excerpted via OCR from an article which first appeared in The TEXAS CAVER
IMPORTANT NOTE: This work is over 20 years old
and some of the information regarding treatments and immunizations is
out-of-date. Do not rely on it for accuracy when looking for or prescribing
rabies treatment or immunizations.
Down in the dark of caves live the bats, and down in the dark of
the bats lives a particularly nasty little virus of the Rhabdovirus
group. It is the rabies virus. All warm blooded animals are susceptible to its
infection; recovery from the disease in man is rare, almost non-existent.
Rabies in man is manifested in four stages: a short prodromal
phase, a sensory prodromal phase, a sensory phase, a period of excitement, and
the paralytic phase. The first, prodromal, usually occurs 14 to 21 days after
infection and is symptoms are by malaise, anorexia, headache, nausea, sore
throat, and/or fever. The patient later begins to show increasing nervousness
and apprehension with lacrimation, pupil dilation, increased difficulty in
swallowing, and perspiration. (The difficulty in swallowing due to terrifically
painful muscle spasms of the throat led to the patients 'fear of water' or
drinking, from which came the name 'hydrophobia'. ) The excitement phase occurs
3 to 5 days from onset and is characterized by seizures, convulsions, and death.
If the patient survives the third phase, he becomes listless, stuporous, and
finally comatose, followed by death. All infections of rabies were held to be
fatal until 1970 when a single recovered case was documented.
Bats infected with rabies react differently than their human,
spelunker-type counterparts. Bats can recover from rabies since, in some
peculiar way, the virus adapts itself in a nonpathogenic manner to the
chiopteran salivary glands. Vampire bats transmit rabies for months without ever
showing a sign of the disease. Even if you catch the little rascal who nipped
you, its brain tissue may not show rabies virus even though yours will shortly.
Almost half the infected bats showed no inclusion (Negri) bodies which is a
positive test for rabies and many harbor the virus only in their salivary glands
and brown fat. Remember, you can't detect most viruses microscopically. Since
1964 there have been 321 cases of rabies in bats reported. When one considers
the difficulty of determining bat rabies, the number of unchecked bats, and the
number of bats whose bite could mean rabies for a caver, it gets a little
Since 1950 there have been six human rabies cases attributed to
bat bites. Bats spread the virus in two ways: entrance of rabies virus
containing saliva into human circulation via a bat bite and, aerosol
transmission of the virus in bat infested caves.
The rabies virus was recently discovered in colonial and
non-colonial frugivorous and insectivorous bats in the US. Bats are able to
transmit rabies to humans and quadruped mammals. The virus does occur in Mexican
Freetailed bats and healthy bats of this genus show a large percentage of
antibodies against the disease. Infection of the Mexican Freetail may be due to
the fact that they winter in Mexico with Vampire bats, especially notorious for
their rabies carrying abilities. Transmission from one species to another
accounts for this. If you are bitten by a bat, cleanse the wound thoroughly. No
wound closures are advised. Next, resign yourself to the rabies series since, if
your bat is infected, there's only a 50:50 chance of proving it, meaning that
you have a 50:50 possibility of getting it, even if the bat proves negative.
This means 14 to 21 single daily injections of the infamous "belly-type". If you
are over 15 years of age and are given heterologases antirabies series, you run
a 46% chance of developing serum sickness. Happily though, a new human
antibody-antisera that doesn't provoke allergic reactions is now being evaluated
for human use. Oh yes, you should also get a tetanus shot if you're bitten.\par
Now, since the aerosol transmission was proven, a caver is faced with the
unpleasant thought of waking up some two weeks after a caving trip with malaise,
anorexia, headache, et cetera. No case of human rabies by aerosol transmission
has been documented to date, however. Unfortunately, by this prodromal phase,
it's probably too late for the rabies series.\par An alternative to the rabies
series (post infection prophylaxis) is the 'pre-exposure' immunization. Two
types of vaccine are now used in the US: duck embryo vaccine (DEV), and nerve
tissue vaccine (NTV). DEV is prepared in embryohated duck eggs infected with the
Pasteur rabbit-brain-fixed-virus and is then inactivated with propbio lactone.
NTV is a rabbit brain tissue preparation infected with a fixed virus and
inactivated by phenol and incubation at 37C, or UV irradiation. The NTV are
dangerous since the foreign rabbit brain material may sensitize the person
vaccinated and produce allergic encephalitis and paralysis. Sometimes the
chances of getting these side effects are greater than the chance for
contracting rabies. All of this is due to an antigen antibody reaction which
reacts with the patient's brain antigen and causes inflammation and
degeneration. Duck embryo is most often used in the US. It markedly reduces
chances for encephalitis, but anaphylactic reactions and post treatment
paralysis have been reported. DEV is given by injection on two possible
schedules: two doses, one month apart followed by a third, six months later, or
three weekly injections with a fourth dose three months later. Booster
immunization should be obtained every two to three years and effectiveness
confirmed by a serum-neutralization test.
The vaccine is available from the State Health Department, and
in some instances, the County or City Health Units, usually free of charge. Your
family doctor can also prescribe it for you, at a higher cost of course, from
your favorite drugstore.
The injections are virtually painless, but some recipients
report very minor itching and inflammation in the area of the injection for
several days following. Your lymph glands will defiantly swell, and any blood
tests taken for the next week or so will show high levels of white blood cells.