Rabies is a viral disease of mammals, transmitted through contact
with saliva from infected animals (i.e. bites, scratches, licks on broken skin
and mucous membranes). Rabies virus infects the central nervous system, causing
encephalopathy and ultimately death, which usually occurs within days of the onset
Where is rabies usually found?
has been found in most countries of the world; it is rare in Western Europe (though
it is moving westward again) and Australia, as well as the polar regions.
common is rabies?
Estimates from the WHO suggest that there are over 50,000
deaths from human rabies each year. The vast majority of these occur in Asian
countries where canine rabies is endemic. In most of Africa and Asia, the mortality
data is unreliable and almost certainly under-reported.
is rabies transmitted?
The most common mode of transmission is by a bite
from an infected animal; typically dogs, but most other small mammals have been
possible carriers, including bats, monkeys, foxes.
rabies be spread from person-to-person?
Transmission between human beings
is possible through biting, scratching or other contact with infected saliva.
There are several reported cases of transmission via transplanted organs, including
donor corneas. There is at least one case of transplacental transmission to a
baby, and others of transmission via breast milk. Transmssion is not airborne,
but aerosol infection - inhalation or ingestion of saliva, or eye infection -
is theoretically possible.
Who is most at risk?
living in infected areas, and those working with infected animals or people with
the disease. Higher risk groups include wildlife officers, veterinarians and people
travelling overseas who expect to have contact with unvaccinated mammals that
bite or scratch.
What are the symptoms of rabies?
develops in two phases:
The prodomal phase (prelude)
may include headache and pain at bite site, often with vomiting and loss of appetite.
Autonomic effects can include copious salivation and weeping.
Throat spasm, and difficulty in swallowing may be followed by progeressive
paralysis. The patient becomes terrified of water (hence 'hydrophobia') and becomes
increasingly agitated and hyperactive.
The agitation may include aggression
and biting, with confusion and delirium. Death follows.
is rabies diagnosed?
A definitive diagnosis follows laboratory identification
of the rabies virus in saliva or brain tissue. This makes diagnosis impossible
during the incubation period, and means that a definitive diagnosis is usually
obtained post mortem.
What is the incubation
The usual incubation period for rabies is three weeks to three
months, but this period can vary, and periods of years have been recorded. Only
one out of six bite victims (including untreated people) go on to develop symptoms.
there a treatment for rabies?
Once rabies is symptomatic. Only intensive
care can provide support. there is no cure; many antiviral agaents have been used,
none with any success.
Post-exposure prophylaxis has a role; if the animal
that bit the patient is identified, it can be observed for ten days; if it develops
symptoms, it can be killed and examined for the disease. If it was a wild animal,
it is normally killed immediately. This can provide evidence that the bite victaim
is at risk, without waiting for symptoms (which would be too late).
post-exposure prophylaxis involves wound management and immunization.
debridement of the wound is essential, and in animals has been shown to reduce
the risk of disease progression. The wound is not closed, post debridement, and
human rabies immunoglobulin is applied to the area (passive immunization). An
intramuscular injection of the immunoglobulin is given to provide some immediate
This is followed by active immunization, using human diploid
cell vaccine. This is usually a course of five injections into the deltoid muscle,
and 5 doses are usually given.
What is the
prognosis for rabies?
While only one in six bite victims go on to contract
the disease from the infected animal, rabies is 100% fatal if untreated.
is the mortality rate for rabies?
Once symptoms have appeared, the victim
usually dies in spite of subsequent immunization and treatment with rabies immunoglobulin.
There are only three documented cases of patients recovering from rabies infection.
000 - 60 000 human deaths from rabies are estimated to occur annually, despite
the existence of an effective vaccine for postexposure prophylaxis (PEP)(at least
10 million doses of rabies PEP are used annually).
In some countries, mortality
is very low (for example, the USA has about one case per year)
mortality is seriously underestimated, especially in Africa. For example, Tanzania's
human rabies mortality is estimated to be about 1500 deaths per year (about 5
deaths/100 000 persons), but national statistics report fewer than 200 deaths
Is there a way to prevent infection?
vaccine can help to prevent rabies. People who handle or come into contact with
animals that may be affected should receive a course of vaccinations.
sense precautions and appropriate training for professions is a much better guarantee
of safety. Domestic animals and browsing or grazing animals are not considered
a significant risk; but dogs, bats, monkeys and other mammals have been implicated
- usually foxes in Europe.
What is the rabies vaccine?
vaccine provides immunity to rabies when administered after an exposure (postexposure
prophylaxis) or for protection before an exposure occurs (preexposure prophylaxis).
The effectiveness of post-exposure vaccination depends on the delay in availability,
and the site of the bite
Who should get vaccinated
Pre-exposure vaccination is recommended for people in
high-risk groups, such as veterinarians, animal handlers, laboratory workers and
others whose activities bring them into direct contact with rabies virus or potentially
rabid bats, raccoons, skunks, cats, dogs, or other species at risk of having rabies.
there adverse reactions to the rabies vaccine?
There are no contraindications
to post-exposure treatment. In the case of allergic reaction, alternative forms
of the vaccine may be used.
There is a failure rate of about one per million
post-exposure treatments. Most of these have been associated with severe lesions
at or near the head, or errors in administration of the treatment.
diploid cell vaccines, pain, erythema and swelling or itching at the injection
site occur among 30%74% of patients. Systemic reactions involving headache,
nausea, abdominal pain, muscle aches or dizziness occur in 5%40% of vaccinees,
and allergic oedema in 0.1%. Systemic allergic reactions characterized by generalized
urticaria accompanied in some cases by arthralgia, angiooedema, fever, nausea
and vomiting have been reported in up to 6% of persons receiving a booster dose,
with onset after 221 days.
Purified Vero cell rabies vaccine produces
local and general reaction in 10.6% of patients and complaints of mild to moderate
reactions in 7%. Low-grade fever was the only significant systemic event, occurring
in 8%, usually following intramuscular vaccination. Pruritus at the injection
site has been the only significant local reaction.
the use of purified
chick embryo cell vaccine has produced local side-effects in 16.4%, with 15.1%
reporting general symptoms.
Can rabies be controlled
Rabies contracted from canine bites accounts for more
than 99% of all human rabies. Scandinavian countries eradicated rabies by environmental
measures including stray dog control. The UK has relied heavily on quarantine
and importation of mammals controls, but does have a program of dog control.
programs have included attempts to vaccinate foxes to create an immune barrier
at the entrance to the Rhone Valley; Switzerland has been freed of rabies. Research
Is there legal protection for workers and
People who contract rabies - and there families - may have a strong
legal case, depending on the circumstances. many places have laws that demand
vaccination of certain pets; any pet owner who fail to maintain up-to-date pet
vaccination may be liable. Wild animals may be subject to quarantine or movement
restrictions, and handlers who flout these laws will be liable.
On the other
hand, individuals who are warned of risks and given advice on protection, and
are subsequently bitten through ignoring the information, may have little right
Legal advise should be sought, as the circumstances will always
vary, and it will depend on local and national laws in your country.
can be learned from history?
Studying cases of rabies has helped to establish
how effective the vaccine can be, and who will beneift; studies of the spread
of the disease across continents can enable governments to alter regulations as
neede to protect the population. For example, over the past twenty years, rabies
has spread westward across Western Europe, with increased incidence in Germany
and France. So the UK has relaxed it's once-draconian quarantine regulations,
and reduced the publicity displays at ports and airports. Go figure!
and Further Information Sources
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Article written by Andrew Heenan BA (Hons), RGN, RMN