All about Rabies :
Rabies is a viral infection that
mainly spreads through a bite from an infected animal. It is an RNA virus of
the Rhabdoviridae family.
Without
early treatment, it is usually fatal.
The virus
can affect the body in one of two ways:
- It enters the peripheral
nervous system (PNS) directly and migrates to the brain.
- It replicates within muscle
tissue, where it is safe from the host’s immune system. From here, it
enters the nervous system through the neuromuscular junctions.
Once
inside the nervous system, the virus produces acute inflammation of
the brain. Coma and death soon follow.
There are
two types of rabies.
Paralytic
or “dumb” rabies: Paralysis is a dominant symptom.
Furious,
or encephalitic rabies: This occurs in 80 percent of human cases. The
person is more likely to experience hyperactivity and hydrophobia.
Vaccinate dogs and cats to protect them from rabies.
Transmission
Rabies is most common in
countries where stray dogs are present in large numbers, especially in Asia and
Africa.
It is passed on through
saliva. Rabies can develop if a person receives a bite from an infected animal,
or if saliva from an infected animal gets into an open wound or through a
mucous membrane, such as the eyes or mouth. It cannot pass through unbroken
skin.
In the U.S.,
raccoons, coyotes, bats, skunks, and foxes are the animals most likely to
spread the virus. Bats carrying rabies have been found in all 48 states that border
with each other.
Any mammal can harbour and
transmit the virus, but smaller mammals, such as rodents, rarely become infected or transmit rabies.
Rabbits are unlikely to spread rabies.
Symptoms
Rabies progresses in five
distinct stages:
- incubation
- prodrome
- acute
neurologic period
- coma
- death
Incubation period
This is the time before
symptoms appear. It usually lasts from 3
to 12 weeks, but it can take as little as 5 days or more than 2 years.
The closer the
bite is to the brain, the sooner the effects are likely to appear.
By the time symptoms appear,
rabies is usually fatal. Anyone who may have been exposed to the virus should
seek medical help at once, without waiting for symptoms.
Prodrome
Early, flu-like symptoms, include:
Ø a fever of
100.4 degrees Fahrenheit (38 degrees Celsius) or above
Ø headache
Ø anxiety
Ø feeling generally
unwell
Ø sore throat and
a cough
Ø nausea and
vomiting
Ø discomfort may
occur at the site of the bite
These can last from 2 to 10 days, and they worsen over
time.
Acute neurologic period
Neurologic symptoms develop,
including:
Ø confusion and
aggression
Ø partial paralysis,
involuntary muscle twitching, and rigid neck muscles
Ø convulsions
Ø hyperventilation
and difficulty breathing
Ø hyper salivation or
producing a lot of saliva, and possibly frothing at the mouth
Ø fear of water, or
hydrophobia, due to difficulty swallowing
Ø hallucinations,
nightmares, and insomnia
Ø priapism, or
permanent erection, in males
Ø photophobia, or a
fear of light
Ø
Toward the end of this phase, breathing becomes rapid
and inconsistent.
Coma
and death
If the person enters a coma, death will occur within a
matter of hours, unless they are attached to a ventilator.
Rarely, a person may recover at this late stage.
Why
does rabies cause a fear of water?
Rabies used to be known as hydrophobia because it
appears to cause a fear of water.
Intense spasms in the throat are triggered when trying
to swallow. Even the thought of swallowing water can cause spasms. This is
where the fear comes from.
The excess saliva that occurs is probably due to the
impact of the virus on the nervous system.
If the individual could swallow saliva easily, this
would reduce the risk of spreading the virus to a new host.
Diagnosis
At the time of a bite, there is usually no way to tell
for sure whether an animal is rabid, or whether it has passed on an infection.
Lab tests may show antibodies, but these may not appear until
later in the development of the disease. The virus may be isolated from saliva
or through a skin biopsy. However, by the time a diagnosis is confirmed, it may
be too late to take action.
For this reason, the patient will normally start a
course of prophylactic treatment at once, without waiting for a confirmed
diagnosis.
If a person develops symptoms of viral encephalitis following
an animal bite, they should be treated as if they may have rabies.
Treatment
If a person is bitten or scratched by an animal that
may have rabies, or if the animal licks an open wound, the individual should
immediately wash any bites and scratches for 15 minutes with soapy water,
povidone iodine, or detergent. This might minimize the number of viral
particles.
Then they must seek medical help at once.
After
exposure and before symptoms begin, a series of shots can prevent the virus
from thriving. This is usually effective.
Strategies include:
A fast-acting dose of rabies immune globulin: Delivered as soon as possible, close to the bite
wound, this can prevent the virus from infecting the individual.
A series of rabies vaccines: These will be injected into the arm over the next 2
to 4 weeks. These will train the body to fight the virus whenever it finds it.
It is not usually possible to find out whether the
animal has rabies or not. It is safest to assume the worst and begin the course
of shots.
A small number of people have survived rabies, but
most cases are fatal once the symptoms develop. There is no effective treatment
at this stage.
A person with symptoms should be made as comfortable
as possible. They may need breathing assistance.
Prevention
Rabies is a serious disease, but individuals and
governments can and do take action to control and prevent, and, in some cases,
wipe it out completely.
Strategies include:
Ø regular anti-rabies
vaccinations for all pets and domestic animals
Ø bans or
restrictions on the import of animals from some countries
Ø widespread
vaccinations of humans in some areas
Ø educational
information and awareness
In rural Canada and the U.S., agencies have dropped
baits containing an oral vaccine to reduce the number of wild raccoons with
rabies.
In Switzerland, the authorities distributed
vaccine-laced chicken heads throughout the Swiss Alps. The foxes immunized
themselves by consuming the vaccine, and the country is now almost free of
rabies.
Individual
precautions
Individuals should follow some safety rules to
reduce the chance of contracting rabies.
Ø Vaccinate pets:
Find out how often you need to vaccinate your cat, dog, ferret, and other
domestic or farm animals, and keep up the vaccinations.
Ø Protect small
pets: Some pets cannot be vaccinated, so they should be kept in a cage or
inside the house to prevent contact with wild predators.
Ø Keep pets
confined: Pets should be safely confined when at home and supervised when
outside.
Ø Report strays to
the local authorities: Contact local animal control officials or police
departments if you see animals roaming
Ø Do not approach
wild animals: Animals with rabies are likely to be less cautious than usual,
and they may be more likely to approach people.
Ø Keep bats out of
the home: Seal your home to prevent bats from nesting. Call an expert to remove
any bats that are already present.
Ø
In 2015, a woman died from rabies after being bitten by a bat during the night. She did
not realize she had been bitten.
People are encouraged to seek medical help after
an encounter with a wild animal, even if they do not have bite marks or other
outward signs of injury.
The World Health Organization (WHO) calls rabies a
“100-percent vaccine-preventable disease.” They note that at least 70 percent
of dogs in an area must be vaccinated to break the cycle of transmission.
In the U.S., vaccinations control rabies in domestic
dogs. Nevertheless, between 30,000 and 60,000 people
seek rabies post exposure prophylaxis every year, following contact with suspect
animals. Hundreds of thousands of animals undergo tests and observation.
Between 60 and 70 dogs and around 250 cats are
reported rabid each year in the U.S. Most of these have not been vaccinated,
and they were exposed to the virus through wild animals, such as bats.
