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Causative Agent |
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Rabies is a
viral disease that leads to
inflammation of the brain
(encephalitis). The virus is a member of the family Rhabdoviridae.
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Worldwide, several variants
of the
virus have been identified, each
associated with a single wild animal host species that acts as a
reservoir of infection for a particular geographic area.
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Images |
Click
on image to
enlarge. |
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Carnivores infected with
rabies, such as this skunk, often show evidence of having
attacked a porcupine. |
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Distribution |
Geographic: |
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Currently, rabies from insectivorous bats is the only known variant of
the virus present in British Columbia.
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Bats confirmed to have rabies have been found throughout BC;
therefore, all bats should be considered as potential
sources of rabies. This is particularly true if bats are
observed behaving abnormally, such as being found during the
day or on the ground.
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Seasonality: |
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The potential for exposure to rabies from bats exists primarily during
the spring and summer months when bats are most active.
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Hosts, Transmission and Life
Cycle |
Hosts: |
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Although all warm-blooded vertebrates are susceptible, only mammals are
important in the spread of rabies.
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In BC, bats are the only
reservoir of rabies. Records of bats
submitted for rabies testing suggest that relatively few are
infected, even among those submitted because they are
behaving abnormally. Bats are a valuable component of the
natural ecosystem and many species are at risk in BC. For
further information on bats and how to live safely with
them, see this
BC Ministry of Environment web page.
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Other potential hosts in BC include domestic dogs
and cats, foxes, raccoons, skunks, wolves (Canis lupus) and coyotes.
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Spill over
of rabies to terrestrial mammals from bats has occurred in
BC, but rabies has never been maintained in wild populations
of terrestrial mammals.
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In BC, rabies acquired
through bites from animals other than bats is unknown;
however, strange behavior in pets and other animals can
suggest that they may have rabies. Avoid contact with any
wild or unfamiliar animal.
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In other parts of
Canada, rabies is found in a variety of wild animals, such
as bats (Vespertilionidae), raccoons (Procyon
lotor), skunks (Mephitidae), foxes (Canidae) and coyotes
(Canis latrans).
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Transmission: |
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Transmission principally occurs through bites of infected carnivores and
bats.
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Rabies can also be acquired if licked by an infected animal OR if saliva
from an infected animal comes into contact with the
mucous membranes of the eyes, nose, lips, or through wounds in the skin.
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The rabies virus does not persist in the external environment; the
virus is rapidly inactivated
through exposure to most detergents, chemicals, ultraviolet
radiation, strong acids and bases, and direct sunlight.
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Life Cycle: |
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Rabies
viruses move from the site of
entry, such as through a wound, and are transported along
nerve fibres towards the spinal cord and, ultimately, the
brain, where the
virus undergoes replication.
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Abnormal behavior results
from the effects of
viral infection in nerve tissues.
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From the brain, rabies
virus is further spread to other
organs via the nervous system.
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The salivary glands, located
in the tissues of the mouth and cheeks, receive high
concentrations of
virus, making saliva an effective
medium for
virus transfer when the infected
animal bites another animal.
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Signs and Symptoms |
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Rabies should be
suspected in any wild animal exhibiting any behavior considered
abnormal, including:
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loss of fear or
unusual friendliness;
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excitation or
aggression;
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depression;
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incoordination;
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paralysis;
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convulsions or seizures;
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abnormal vocalizations;
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appearance of nocturnal creatures during the day;
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signs of choking or inability to drink or swallow food;
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drooling of saliva or frothing at the mouth;
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in carnivores, evidence of having attacked porcupines.
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Bats, unlike many mammals with rabies, may get sick and
die before being observed or showing symptoms typically found in
other mammals.
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Meat Edible? |
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DO NOT
consume meat from an animal with rabies or suspected to
have rabies.
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DO NOT
feed
meat from an animal with rabies or suspected to have rabies to pets.
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Human Health Concerns and
Risk Reduction |
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Rabies is a potentially life-threatening disease for humans; signs of
infection may not be detectable for weeks or months - left untreated, rabies is always fatal.
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Symptoms in humans are similar to those in wildlife:
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depression;
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headache;
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vertigo;
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stiff neck;
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inability to drink (hydrophobia);
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spasms and
paralysis;
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left untreated, death results from swelling of the
brain or
pneumonia.
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Two human deaths
have been attributed to bat rabies in BC. One was a 22-year old
college student bitten by a bat while visiting Alberta in 1985,
while more recently, a 52-year old man died of rabies in January
2003.
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Prevention of rabies depends on 4 basic activities:
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vaccination of domestic animals that live in close
proximity to people and which may be exposed to wildlife
reservoirs of rabies;
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avoid contact with potentially infected animals. Always
consult a health authority if a bat is found in the house. Never
approach any wild animal whether it appears to be acting
normally or not. Never feed wild animals;
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if there is a high risk of occupational exposure to
bats, a rabies vaccination should be considered;
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any person that is bitten, scratched, etc. by an animal
and suspects they have been exposed to rabies should wash wounds
immediately with soap and water, disinfect the wounds with
50-70% alcohol, and contact the nearest health authority and
inform them of the potential exposure to rabies.
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DO NOT go near any animal suspected of having rabies.
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Report any animal suspected of having rabies to the
local
Ministry of
Forests, Lands and Natural
Resource Operations office or the
RCMP.
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Do
not attempt to collect tissues yourself; if possible, submit the
entire carcass for testing. Specimens can be frozen.
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For
small animals such as bats and foxes, double-bag the entire animal
in strong garbage bags and place in a leak-proof container.
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For
larger specimens, contact the nearest
Ministry of Forests, Lands and Natural Resource Operations office
or Ministry of Health office for instructions on where to submit the
specimen.
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Further public health information on rabies can be found
at the
BC Ministry of Health.
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Rabies is a
reportable disease in Canada, and under the Health of Animals Act, all cases must
be reported to the Canadian Food Inspection Agency (CFIA).
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Samples for Diagnosis |
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Intact brain tissue is
the key diagnostic tool in confirming rabies infection. If an animal
suspected of having rabies must be destroyed, it is important that
it NOT be killed by gunshot to the head - other forms of euthanasia must be considered.
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Further Reading |
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Alberta Environment and Sustainable Resource Development –
Rabies (PDF file)
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Alaska Department of Fish and Game – Rabies
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BC
Centre for Disease Control – Rabies
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BC Wildlife Health Fact Sheet – Rabies (PDF file)
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Canadian Centre for Occupational Health and Safety
– Rabies
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US Centers for Disease Control
– Bats and Rabies
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Canadian Cooperative Wildlife Heath Centre. 1995.
Health Risks to Wildlife
Personnel: Hazards from Disease-Causing Agents. Canadian
Cooperative Wildlife Heath Centre, Western College of Veterinary
Medicine, University of Saskatchewan. Saskatoon, SK
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Elkin B., R.L. Zamke. 2001. Common
Wildlife Diseases and Parasites in Alaska. Alaska Department of
Fish and Game. Anchorage, AK.
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Rupprecht C.E., Strohr K., Meredith C. 2001. Rabies. Pp. 3-37 in E.S.
Williams, I.K. Barker (eds.),
Infectious Diseases of Wild Mammals. 3rd Ed. Iowa State
University Press. Ames, IA.
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