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What is it?
Rabies is a disease spread through a virus.
Basically, viruses work like this. Most cells have both DNA (deoxyribonucleic
acid), and RNA (ribonucleic acid). These are the genetic coding, the building
blocks of life. When cells divide, the genetic information is copied and
transferred to each cell. Viruses are one-celled creatures that have only one or
the other. Rabies is an RNA virus. Rabies virus belongs to a group called
Rhabdoviruses, which are bullet-shaped viruses with a hard sheath. Viruses are
incapable of dividing or reproducing on their own, so they use other cells to do
this for them. A virus will attach itself to another cell, such as a blood cell,
and inject its genetic coding into the cell. This changes what the cell does,
from being a red blood cell or a liver cell to becoming a little virus factory.
The virus repeats itself inside the cell over and over until the cell literally
breaks open, and all these little viruses go out and attach themselves to other
cells.
Incidentally, this is one of the reasons why
there’s nothing you can take to cure a cold. There are a lot of different
versions of the cold virus (viruses mutate readily), and because the virus
attacks inside the cell, there is no way for any medicine to reach it. By
allowing yourself to rest, your body’s own defenses (white blood cells) can
attack the viruses. By drinking plenty of fluids, you eliminate these dead white
blood cells and viruses from your system. Diseases like the cold virus are
called opportunistic pathogens. What that means is that these viruses ‘n’
things are always present in the air and on surfaces around us, but most of the
time our bodies are able to ward them off. It’s when we allow our defenses to
get depressed through not eating properly, not getting enough rest, having too
much stress, etc. that the virus can get a start.
There are four levels of damage that viruses
can do. Level one viruses are things that don’t cause many problems, like the
cold virus. Level two viruses are things that are more serious, but not usually
fatal, like polio or hepatitis. Level three viruses are fatal to humans, but
ones where there is a way of dealing with them. Rabies is considered a level
three virus. Level four viruses are those that are fatal, and for which there is
no way of dealing with them. Ebola is considered a level four virus. During the
black plague of the Middle Ages, there was about a 40% death rate. Ebola Zaire
has over a 90% death rate, and it’s highly contagious. There are level four
biocontainment labs at USAMRIID (the U.S. Military) and at the Center for
Disease Control in Atlanta, for example. To work with level four viruses, you
have to be in a space suit type apparatus, and the rooms where these viruses are
kept have a negative airflow. What that means is that if you blew a hole in the
roof, air would flow in, not out. It’s not something you want to mess
with. With Ebola, the skin and muscle tissue essentially liquefies.
Where Does Rabies Come
From?
Rabies virus has been around for a long, long,
long time. There are writings about rabies from Mesopotamia, and on the
hieroglyphics in Egypt. In North America it is thought (but not proven) that the
virus came with the explorers from Europe, traveling in sled dogs and pack
animals. In northern Canada, rabies was historically known as arctic madness or
Eskimo sled dog disease. It was diagnosed as rabies in the 1920’s. In the late
1940’s rabies spread from arctic foxes to red foxes, high in northern Ontario.
From there it spread down into southern Ontario fairly quickly. The open
farmland provided excellent habitat for foxes, and thus for rabies.
Traditionally, Ontario has had the highest incidence of rabies anywhere in
Canada, although there are occasional outbreaks in Quebec and there is some
skunk rabies in Alberta.
How Do Viruses Spread?
Most viruses spread from individual to
individual through the air or through inter-surface contact. Within the body,
most viruses travel through the bloodstream. Rabies virus is an exception in
that it only travels within the body through nerve cells. Once the virus has
access to a nerve cell, it will travel along the peripheral nerves to the spinal
column, then along the spinal column to the brain. Once it has a good stronghold
in the brain, it will spread fairly quickly throughout the whole body. One of
the places it goes is to the salivary glands. There, the virus transfers what
the salivary glands do (making saliva so you can chew and swallow your food) to
becoming little virus factories. It is often said that a rabid animal foams at
the mouth. This is because the animal is producing a lot of saliva, and the
saliva has rabies virus in it. The virus also changes the animal’s behaviour
so that a rabid animal will bite at anything. They’ll bite at rocks, at
sticks, at trees, themselves, and anything in their path. This is how the virus
ensures its spread from one individual to another.
There are four ways to contract rabies:
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What Does a Rabid
Animal Look Like?
Depending on where the virus contacts the body,
it can take more or less time for symptoms to develop. The face is a lot closer
to the brain than the foot. It’s important to remember that even with a bite
wound, the virus must contact a nerve cell in order to proliferate. If the virus
can’t contact a nerve, it will die within a short period of time. Before
Pasteur developed the first rabies vaccine, about 40% of people attacked by
rabid animals developed the disease. It’s not something you want to take a
chance on. Normal gestation (from point of contact to symptoms) of the virus
usually takes about three weeks. However, there have been cases where the virus
has taken up to two years to become active. It is vital to take action quickly,
as once symptoms develop the virus has taken over the brain. There have been a
couple of cases of humans who have survived rabies, but they had virtually no
cognitive function (a "vegetable").
There are generally acknowledged to be two
forms of rabies, the fierce form and the dumb form. Often one is the progression
of the other. Once the animal begins to display symptoms, it has at most five
days to live, often a day or less. There have been a few cases where an animal
was shedding virus through the saliva but not showing symptoms and vice versa,
but most often these begin around the same time. A raccoon that panhandles in a
park is not showing signs of rabies, even if it displays mild aggression. A
rabid animal will wander around as if drunk. Paralysis develops in the hips, so
often the animals will have difficulty walking, staggering around. It will
attack or bite at anything, unprovoked. With cattle, they often bellow and seem
agitated. Cats are more likely to become fierce. As the disease progresses,
there is a swelling in the throat that compresses the trachea. Eventually the
animal is unable to move or breathe and it asphyxiates.
What Animals Carry
Rabies?
ANY mammal, any animal with hair or fur, can
contract rabies. This includes humans. One question children have asked me a lot
is, "Can whales get rabies?" Technically, yes. However, it’s unlikely a
rabid animal would get close enough to a whale to spread the virus.
The animal that is the dominant carrier of the
virus in a region generally classifies rabies as the type for that region. For
example you have coyote rabies in Texas, the Mississippi skunk strain, and raccoon
rabies and fox rabies here in Ontario. It is vital to note that any mammal
can get any kind of rabies. These species are the dominant carrier of that
type, mostly because they are most likely to be in contact with animals of the
same species. The raccoon strain is particularly virulent, affecting a wide
variety of species quite readily. Historically, we have had fox rabies in
Ontario. Raccoons and coyotes have been a little more resistant to that strain
of rabies, but virtually all skunks in Ontario that have had rabies were
infected by the fox strain. On the grossest level, it’s all rabies virus.
Using fancy PCR techniques, you could separate fox rabies from Windsor from fox
rabies from Ottawa.
Fish don’t get rabies; neither do insects,
reptiles, amphibians or birds. Having said that, there was one case of a young
owl in France that contracted rabies. It is the only known case in history. Some
species of raptors, especially Great-Horned Owls have been known to be carriers
of the virus in their bloodstream because of predation on skunks. Their internal
body temperature is too high for the virus to spread so they don’t contract
the disease, nor do they spread it.
In Ontario, the main rabies vector (until the
past few years) has always been the red fox. Ever since rabies moved into
southern Ontario in the 1950’s, Ontario has had the dubious honour of having
the highest incidence of rabies in Canada. Because an outbreak of rabies can
kill most of the animals of a given species in an area fairly quickly, it takes
time for the population of animals (and rabies) to rebuild. Rabies in Ontario
generally runs on a four-year cycle of diminish and rebuild until the next
outbreak.
In 1967, a stray cat scratched a little girl
near Ottawa and she died of rabies. That was the last fatal human rabies case in
Ontario. It also marked the beginning of the Ontario Ministry of Natural
Resources Rabies Research program. Over the years the Rabies Unit developed a
strategy to deal with rabies using bait containing a rabies vaccine. The project
has included a number of agencies, both public and private. It remains a
co-operative project. After several years of doing small-scale projects, the
Rabies Unit began a large-scale project in eastern Ontario in 1989. The area
from Ottawa to Brockville had a very defined rabies cycle, with very obvious
patterns of highs and lows. There was an average of 400 cases per year in that
zone. They began large-scale baiting in 1989, and the last rabid fox in that area
was in 1993.
Raccoon rabies in the U.S. was traditionally
confined to Florida, Georgia, Louisiana and the southern part of South Carolina.
Over twenty years ago, a group of raccoon hunters from West Virginia who had
shot all the raccoons in their area went down to Florida, loaded up 3500
raccoons, and released them in West Virginia. Raccoon rabies came too, found a
susceptible population and exploded up the Eastern Seaboard. It is now found
along the entire East Coast, and is continuing to move north and west. The first
cases in New York State were in the southeastern corner of the state in the
early 1990’s. The disease spread like wildfire through the state, and
approached the Canadian border first in the Niagara region. Because the vaccine
in the bait we developed was designed for foxes, it would not work on raccoons.
Therefore, the Rabies Unit began an intensive program of live trap - vaccinate
and release (TVR), using cage traps to capture the animals and Imrab vaccine
(the same one your vet uses) administered by injection. As the disease moved
east along the southern shore of Lake Ontario, the Unit began a similar program
around the bridgeheads at Gananoque, Prescott, and Cornwall. A vaccine bait
combination has since been developed for raccoons as well.
There are two problems associated with raccoon
rabies that aren’t as prevalent with fox rabies. One is that raccoons are
great hitchhikers. Raccoons have been known to catch a ride on transport trucks,
boat trailers, and trains. The other problem is that they live close to humans,
and humans tend to think they’re cute. When raccoon rabies first entered New
York State, there was a raccoon rehabilitator who wanted to take some raccoons
five counties west from an epizootic area, and release them in a county where
the rabies had not yet progressed. He was caught by the New York State Troopers
and sent home. He then went on the local radio station, proclaiming himself some
sort of raccoon vigilante, saying that he was going underground and the
authorities couldn’t stop him from releasing those animals. We had at least
one known case in Ontario where a man live-trapped a raccoon in his backyard in
Toronto, but didn’t want to kill it. So, he took it to his cottage three hours
away and released it. The first cases of raccoon rabies in Maryland were fifty
miles over the border, near a garbage dump. The first case of raccoon rabies in
Ontario was some 50 kilometres north of Brockville in a well-known raccoon
"dumping zone" for the city. There are wooded parks in Toronto that
have up to 100 raccoons per square kilometre! A lot of humans mean a lot of
garbage, and to raccoons that means a lot of food.
A note about relocation and bounties: First,
the Rabies Unit did an experiment where several raccoons were live-trapped in
Toronto and released in the country north of the city. Farmland, an idyllic
situation… All the released animals were dead within three months. Because
there is such a high population of raccoons already, the released animals were
unable to find a home range. Some were hit by cars; others starved to death.
Second, nature hates a vacuum; if you remove a lot of animals from an area,
either by poisoning, bounty or relocation, you encourage other animals from
outside the area to immigrate to fill the void. They bring with them their own
diseases, parasites, etc. Over the past hundred years or more, coyotes have been
shot, trapped, poisoned, exploded, and there are more now than there were then.
Finally, if you relocate an animal, you also relocate any diseases it may be
carrying.
As our urban areas continue to expand and chew
up more and more habitat, human/animal interactions are more and more common.
This is especially true of the people who buy houses with those nice ravine lots
at the back. These are the people who call every day to complain about the wildlife in
"their"
back yard.
Dealing with Rabies
It must be noted that there is no known "cure"
for rabies. For people such as myself who work around rabid animals there is a
pre-exposure inoculation to raise the body’s ability to deal with casual
contact. For anyone who has been in contact with a rabid animal there is a
post-exposure treatment. Anyone who had rabies shots 30 years ago will be
pleased to know that the treatment has changed. The original rabies treatment
(the Semple treatment) consisted of autoclaved brain tissue (steam
"cooked" to sterilize) that was injected directly into the abdomen.
There was no way to get it absorbed into the bloodstream directly, so it had to
be absorbed through the intestinal wall. After the required shots, the whole
abdomen turned into a huge red welt.
That system hasn’t been used for some time.
Post-exposure treatment now consists of five shots in the arm over a period of a
month, plus one hemoglobin shot to boost the immune system.
Now, only a doctor is qualified to give medical
advice, and only a doctor can prescribe post exposure treatment. If you are in
contact with a suspected rabid animal, try to save the specimen if possible,
especially the head. The brain will be sent to the Agriculture Canada Rabies Lab
for testing. The first thing you can do is to wash the contacted area with soap
and water, then contact your physician or the local emergency ward. If a pet has
been in contact with a potential rabid animal, the same applies. Take cautions
with the animal, and contact your vet as soon as possible. If it is a pet
contact and the attacking animal is confirmed rabid (or if it escapes), the vet
will likely recommend complete quarantine or euthanasia.
If you come across a dead animal on your
property and there is no possibility of contact from anyone or any pet, then
either wrap it well in several garbage bags (turn the bag inside out, then
envelop the animal) and/or bury it deep enough that it won’t be dug up. If
you must handle the animal, use a shovel or, if absolutely necessary, use heavy
rubber gloves. Use a bleach solution to disinfect everything.
If you find a dead animal on your property or a
road-killed animal, the question becomes, "Is it still rabid?" It depends on
two factors: time and temperature. Temperature is the more important factor.
There is an old trappers’ saying that if you find an animal you suspect to be
rabid, you should freeze it before handling. Absolutely the worst thing you can
do. Freezing does not kill rabies virus. The virus will go into a
suspended state, only to awaken on thawing. An Agriculture Canada experiment put
a rabid animal in a freezer at -30 deg. C for two years. When the carcass was
thawed, the virus was still active! Rabies virus in a petrie dish at room
temperature will remain active for a few days. In a summer, roadside condition,
the virus around the surface of the animal would probably die within half an
hour, but the virus in the brain would be viable for several days. There is no
way to guarantee that any dead animal did or did not have rabies without a brain
test. During the rabies enzootic experiment in eastern Ontario, about 50% of the
road-killed foxes we received were rabid! About the same percentage of animals
with quills were rabid. Several animals with quills were young and likely very
hungry; one was 10 ½ years old (Methuselah for foxes). Many road kills were
also young and inexperienced. Better to err on the side of caution.
If you find a dead animal that you want to
skin, especially if you want the skull for a sample, be VERY careful. Remember
that rabies can be fatal, but it is not the ONLY disease or condition out there.
Some of them are transferable to humans. Wear rubber gloves and a rubber apron.
Wear eye protection and a kevlar glove on the hand not holding the knife.
Disinfect everything with a bleach solution. If you prick yourself with a
knife or bone, contact your doctor. Use common sense. At this time, raccoon
rabies is confined to eastern and central Ontario. Fox rabies is still present
in small amounts in pockets around the southern part of the province. Remember
that other species of mammals can also get rabies.
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