| Rabies in Dogs: Symptoms,
Diagnosis, Treatment & Vaccination |
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| FACTS |
Rabies is one of the best known of all the viruss. The mere mention of
the disease can bring back vivid memories of Old Yeller. Who among us does
not picture a large yellow dog foaming at the mouth and acting aggressively
and out of its mind looking to bite anyone or thing that crosses its path.
While this is a common stereotype, this is actually a rarely seen scenario,
in the United States that is. Fortunately, through active vaccination and
eradication programs, rabies only accounted for 4 human deaths in the United
States in 1997. In other parts of the world, however, human cases and deaths
from rabies are much higher. In fact, some estimates claim that human death
rates may be over 10,000 a year in southern Asia.
If you want to completely avoid coming into contact with a rabid animal you
should move to Australia, the British Isles, or Antarctica where there is no
rabies virus. When traveling around the world, you will encounter certain
animals that are much more likely to be carriers of the disease. After
leaving the safety of the British Isles and heading eastward into Europe,
the fox is the primary carrier. If you dip south into Africa, you will
encounter it in jackals in the north, dogs and cats in the central
countries, and mongooses in the southern part of the continent. Heading into
the Himalayans, you can see it in wolves and in Russia it is seen in dogs.
The arctic fox is the main carrier in all parts of the Arctic. If you
venture into Indonesia and Malaysia, the dog and cat are again common
carriers. When you come back to South America, the dog and cat are again
common sources of exposure as well as vampire bats.
In Mexico, insectivorous bats cause the most problems. In the United States,
the mountain states have the lowest incidence of humans contacting animals
with rabies. When you hit the Plains, the Midwest, and Texas the striped
skunk is the big carrier. As you work your way to the east, raccoons become
important carriers. Fox and bats also cause some human exposures, but very
rarely, especially the bat who gets blamed more than it should. If the
squirrel or rabbit in the back yard bites you, do not panic, there has never
been a reported case of someone contracting rabies from one of these
species. |
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| WHOS AT RISK |
| People that work closely with wildlife, veterinarians, and travelers are
at the highest risk of exposure. Fortunately, there is a vaccine that is
available to protect high-risk people. Animals that come into contact with
wildlife and are not vaccinated, are at a higher risk of exposure. While the
risk of coming into contact with the virus is very low, it nevertheless does
exist. When I started my first job in rural Wisconsin, a veterinarian I
worked with told me that in over twenty-five years of practice he had never
seen a case of rabies. Two years later, I was exposed to two dogs and a cow
in one three-week period that all had, and died from, rabies. Because of the
movement of carriers, there is always the risk of exposure. In my three
cases, there was known contact with raccoons by both dogs and a skunk by the
cow. |
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| transmission of the disease |
| The transmission of the disease almost always occurs as a result of an
infected animal biting a non-infected animal. There have been a few reported
cases of infection resulting from aerosolization occurring in caves where
large quantities of infected bats reside. Rabies virus does not live very
long outside the host and remains viable in the carcass of an infected
animal for less than 24 hours. The rabies virus is shed at high levels in
saliva. However, being bitten by a rabid animal does not necessarily mean
that the animal will become infected. It has been speculated, that only
around 15% of exposed people will contract the disease. Humans, dogs, and
cats are only mildly susceptible to the disease unlike skunks, raccoons,
foxes, and bats that are much more susceptible to the virus. |
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| SYMTOMS |
| After coming in contact with the virus, the bitten animal may go through
one or all of several stages. If the bitten animal is a skunk it may not
show any symptoms at all but could become a lifelong carrier. With most
animals, however, the virus will spread through the nerves of the bitten
animal towards the brain. The virus is relatively slow moving and the
average time of incubation from exposure to brain involvement is between 3
to 8 weeks in dogs, 2 to 6 weeks in cats, and 3 to six weeks in people.
However, incubation periods as long as 6 months in dogs and 12 months in
people have been reported. After the virus reaches the brain it then will
move to the salivary glands where it then can be spread through a bite.
After the virus reaches the brain the animal will show one, two, or all of
the three different phases. |
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| prodromal phase |
| The first is the prodromal phase and usually lasts for 2-3 days in dogs.
Apprehension, nervousness, anxiety, solitude, and a fever may be noted.
Friendly animals may become shy or irritable and may snap, whereas,
aggressive animals may become affectionate and docile. Most animals will
constantly lick the site of the bite. In cats, the prodromal phase lasts for
only 1-2 days and they usually develop more fever spikes and erratic
behavior than dogs. |
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| furious PHASE |
| From the prodromal phase, animals may enter the furious stage; cats are
particularly prone to developing this phase. The furious stage of the
disease in dogs usually lasts for 1 to 7 days. Animals become restless and
irritable and are hyperresponsive to auditory and visual stimuli. As they
become more restless, they begin to roam and become more irritable and
vicious. When caged, dogs may bite and attack their enclosures. Animals
progress to become disoriented and then have seizures and eventually die. |
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Paralytic (dumb) phase |
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Animals may develop the paralytic phase either after the prodromal or
furious stage. The paralytic phase usually develops within 2 to 4 days after
the first signs are noted. Nerves affecting the head and throat are the
first to be involved and animals may begin to salivate as a result of their
inability to swallow. Deep labored breathing and a dropped jaw may result as
the diaphragm and face muscles become increasingly paralyzed. Animals may
make a choking sound and many owners think that there is something lodged in
the dog’s throat. This was the case with both dogs I was exposed to (as
mentioned earlier) and the owners were also exposed as they had been looking
in the dog’s mouth for a foreign object. The animal will get weaker and
eventually go into respiratory failure and die.
As a side note, many of the dogs with rabies that I encountered while in
Central America also presented with the dumb form. The one cow that I saw
bellowed incessantly and staggered aimlessly. Many animals present with a
combination of the above symptoms and phases.
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| Diagnosis |
| The current way to diagnose rabies in animals is to submit the brain for
microscopic exam. Some new testing techniques utilizing skin and or blood
samples are being studied and used in a few research settings and show
promise as a way of testing potentially exposed humans and animals. They are
not routinely being used at this time. |
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| TREATMENT |
| There is no treatment. Once the disease develops in humans, death is
certain. There have a couple of reported cases of dogs surviving the
infection, but they are very rare. |
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| Vaccination and prevention |
Vaccination is the best way to prevent infection and properly vaccinated
animals stand very little chance of contracting the disease. While rabies
vaccination for dogs is mandatory for all states, it is estimated that up to
half of all dogs are not vaccinated. Some communities are also requiring
cats to be vaccinated, which is very important because there are currently
more cases of cat rabies than dog rabies. Some people estimate that less
than ten percent of the cat population is vaccinated thus leading to the
high incidence of rabies in cats. The standard vaccination protocol is to
vaccinate dogs and cats at three or four months and then again at one year
of age. After the 4-month-old initial vaccine a three-year rabies
vaccination is recommended. The three-year shot has been tested and shown to
be very effective. A few counties, states, or individual veterinarians
require yearly or once every two-year vaccination for a variety of reasons
that need to be explored more closely. There is also a rabies vaccination
available for high-risk people.
There are some vaccines available for large
animals also. The question of vaccinating exotic animals is a common one.
There are no approved products for most
exotics, however, canine vaccine is used on some species to offer some
protection. Vaccinating exotics or wolf
hybrids should be dealt with individually in cooperation with your local
veterinarian. Keeping a wild animal that is at high risk of being a carrier
such as a skunk or raccoon is never recommended. |
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| HUMAN EXPOSURE |
| If an animal bites a human, the animal will be either quarantined or
observed for a period of at least ten days to ensure that it does not have
rabies. Whether or not the animal was currently vaccinated the community
that you live in will dictate the requirements of the quarantine. People
that do become exposed to a rabid animal can be given a five-shot post
exposure series of Human Rabies Immune Globulin to protect them against
being infected. There is a three-shot series of Human Diploid Cell Vaccine
that can be used to vaccinate people at high risk. |
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| SUMMARY |
| All warm-blooded animals are at risk for contracting rabies, however,
some species are much more resistant than others. Transmission of the virus
is almost always through a bite from a rabid animal. There are a variety of
different symptoms and once contracted there is no cure, and death is almost
always the outcome. The disease is very preventable through vaccination.
While relatively rare in humans, the risk of contracting it, and the outcome
of the disease make precaution with wild animals and vaccination of domestic
ones essential. |
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| host: The organism in or on which a parasite lives. For example, dogs and
cats are hosts for fleas and roundworms. |
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respiratory: Relating to breathing or the
lungs.
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| VIRUS: The smallest form of life, invisible
with an ordinary microscope. An infectious unit that enters and uses cells
of plants or animals for replication. Some viruses cause disease in animals
or plants. |
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| Carrier: An animal which harbors an infectious
organism, such as a virus, bacteria, or parasite. The animal does not appear
ill, but can still transmit the organism to other animals by direct contact
or releasing the organisms (bacteria, protozoa, viruses) into the
environment in the stool, urine, respiratory secretions, or vaginal
discharges. |
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| There is no treatment. Once the disease develops in humans, death is
certain. There have a couple of reported cases of dogs surviving the
infection, but they are very rare. |
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