Rabies
Rabies is caused by a virus from a group of viruses called the
lyssavirus genus. The rabies virus is transmitted in saliva and
can infect any fresh wound, thus bite wounds from infected animals
are the most common source of infection. Once in the body the
virus is spread via the nerves to the central nervous system (the
brain). Rabies can infect most animal species, including humans.
The United Kingdom, Australia, New Zealand, Japan, Singapore,
Papua New Guinea, Iceland and the Pacific Islands are reported
to be free of the Rabies. In Australia a virus called Bat Lyssavirus
was identified in 1996, and extensive testing has shown that it
is not the same as rabies.
Throughout the world there are two cycles of infection, the ‘urban’
cycle and the ‘sylvatic’ (wildlife) cycle.
Urban Cycle- Dogs account for 99% of all human rabies deaths and
they are the main carriers of the virus within the urban environment.
The virus is spread between dogs as a result of fighting. This
is more commonly a problem in countries such as Asia, Africa and
South America where vaccination is less frequently undertaken.
In North America and Europe rabies in dogs is mainly controlled
by vaccination.
Sylvatic Cycle- Different regions in the world have different
wildlife and therefore different carriers of the virus. Some
examples include raccoons, foxes, skunks, weasels, stoats, jackals,
wolves, bats, mongooses and meerkats. Bat droppings are also a
potential source of infection through skin wounds and mucous membrane
(eyes and gums) which is of significance when entering caves containing
bat colonies.
Signs of an infection may take between 10 days and 6 months to
become apparent from the time of infection. Once clinical signs
are recognized it is unusual for the animal to survive more than
10 days as there is no effective treatment.
The following signs described below relate to the dog however
they area similar for all animal species. No one set of signs
is definite, so any unvaccinated animal with sudden onset of nervous
signs should be considered as a potential rabies case and handled
with caution.
There are 3 separate stages of rabies each with its own distinct
appearance.
Prodromal Stage- this is the 1st stage of rabies and occurs in
all cases. It only lasts 2-3 days and is easy to miss for someone
not well accustomed to the dog. The dog’s personality changes,
dogs that are normally shy can become friendly, and dogs that
are normally pleasant can become nasty and wary. The dog will
then develop signs of either the ‘dumb form’ or ‘furious form’.
‘Dumb Form’- The dogs face and neck muscles can become paralyzed.
They have profuse saliva dripping from their mouth and can’t
swallow properly. The dogs are not vicious and rarely attempt
to bite unless provoked. The paralysis spreads throughout the
body and the dog slips into a coma and dies. Owners attempting
to look within the dog’s mouth risk exposing themselves to the
rabies virus.
‘Furious Form’- The dog becomes restless and its pupils may dilate
(the black part in the middle of the eye becomes much larger).
They often appear to have a puzzled or apprehensive look and
periods of abnormal strength. If the dog is not restrained it
may wildly run around and snap at any nearby objects. The dog
may eat anything during this stage, including stones, soil and
sticks. After a few days the dog will suddenly show ataxia (uncoordinated),
convulsions, and become paralyzed and die.
Diagnosis is usually made by examination of brain tissue after
death.
Pets should be vaccinated at 12 weeks of age then again one year
later. Booster are given every one to three years depending on
the local risk. It is recommended that unvaccinated pets that
are exposed to rabies be euthanased or alternatively quarantined
for 6 months, with no uncontrolled contact with people or other
animals. Pets that have been vaccinated and are exposed to rabies
should be given a booster vaccination and be closely observed.
People intending on traveling to regions where rabies is a problem
should consider vaccination if they intend to be handling animals.
This will require 3 injections over a period of 21 days. The
vaccine is not completely protective and so if exposed it is advised
that medical help is sought immediately. Initial first aid can
include washing the saliva away from the wound with soapy water
and apply a disinfectant. Two additional vaccinations may be
given, but if the person was not vaccinated more will be required.
Related sites
Animal rabies control
Vaccine information and control
Vaccinations
Rabies, distemper, Bordetella and Lyme
Rabies
K9web website
Rabies
Prevention
US Government
Very detailed on all aspects of disease and cycle
Australian Quarantine Service
Quarantine recommendations and world distribution
