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Rabies
Rabies
Kendra McQueen
Jennifer Rasmussen
Edward Guevara
Description
• Rabies is an infectious disease caused by the Lyssavirus of the
Rhabdovirdae family that attacks the nervous system. These are
the only known viruses to travel along the nerves after infection.
The virus is usually in the saliva of a rabid animal and the route of
transmission is nearly always by a bite. By causing the infected
animal to be exceptionally aggressive, the virus ensures its
transmission to the next host. Transmission through the mucous
membranes has occurred by people exploring caves populated by
rabid bats.
• After a bite the virus enters the body and starts to replicate before it
moves to the peripheral nerves. It moves slowly in the nervous
tissue jumping from nerve cell to nerve cell where it eventually
reaches the CNS. At the brain it causes encephalitis and the typical
symptoms of rabies appear. The incubation period for rabies is the
time it takes to get from bite to brain which can be anywhere from 2
weeks to several, months. Bites on the hand and face can move
much quicker to the CNS because of the many nerve endings found
at these sites. As soon as the virus gets to the brain it travels to the
salivary glands, replicates in abundance and is shed in the saliva.
At this point the animal becomes infectious and can transmit the
disease through a bite.
Structure
• The Rabies virion is bullet shaped and contains
a non-segmented, negative stranded RNA
genome that encodes five proteins. It is
approximately 180nm long and 75nm wide. Its
RNA measures at 3000nm.
• The RNA is encased by nucleoprotein, which is
covered by the ribonucleoprotein (RNP) helical
core. Phosphoprotein and polymerase are
associated with the RNP. A matrix protein
covers the RNP and is surrounded by an
envelope.
• The surface of the envelope is covered by
around 400 spike-like glycoprotein10nm long.
Replication
• Attachment: the virus attaches
to the nerve cell.
• Penetration: the virus enters
the cell
• Uncoating: the envelope is
removed.
• Transcription and translation:
the virus replicates.
• Budding: the new virus leaves
the host cell and attaches to
other nerve cells and spreads
from brain to the rest of the
body by the nerves.
Rabies in humans
• The incubation period—the time from exposure to the
rabies virus until symptoms appear—is usually 4 to 6
weeks. In rare cases, the incubation period can last from
several days to more than a year after exposure to the
virus.
• If you are concerned that you may have been exposed to
the rabies virus, it is important to seek medical attention
before symptoms develop. Rabies is nearly always fatal
if not treated before the appearance of symptoms.
Signs and Symptoms
Pain at bite site
Fever
Malaise
Fatigue
Anorexia
Hydrophobia
Inability to Swallow
Cough
Nausea
Vomiting
Sore Throat
Muscle pain
Headache
Nuchal Rigidity Neurological Changes
CNS Damage
Hallucinations
Seizures
Alt Consciousness
Lethargy
Coma
Death
Is rabies a common disease?
• In the United States in 2001, there were 7,437 cases of rabies
reported in animals. Most were in wild animals. One case was
reported in a human. Rabies occurs in almost every state. Hawaii
is the only state that has not had a single native case of rabies in
animals or humans. As you can see by this map, rabies is most
common in the eastern United States.
Rabies Diagnosis dFA Test
Rabies Diagnosis dFA Test
Prevention
• Rabies is preventable!
• Be a responsible pet owner:
• Keep vaccinations up-to-date for all dogs, cats and ferrets.
This requirement is important not only to keep your pets from
getting rabies, but also to provide a barrier of protection to
you, if your animal is bitten by a rabid wild animal.
• Keep your pets under direct supervision so they do not come
in contact with wild animals. If your pet is bitten by a wild
animal, seek veterinary assistance for the animal immediately.
• Call your local animal control agency to remove any stray
animals from your neighborhood. They may be unvaccinated
and could be infected by the disease.
• Spay or neuter your pets to help reduce the number of
unwanted pets that may not be properly cared for or regularly
vaccinated.
Prevention
• Avoid direct contact with unfamiliar animals:
• Enjoy wild animals (raccoons, skunks, foxes) from afar. Do not
handle, feed, or unintentionally attract wild animals with open
garbage cans or litter.
• Never adopt wild animals or bring them into your home. Do not try
to nurse sick animals to health. Call animal control or an animal
rescue agency for assistance.
• Teach children never to handle unfamiliar animals, wild or domestic,
even if they appear friendly. "Love your own, leave other animals
alone" is a good principle for children to learn.
• Prevent bats from entering living quarters or occupied spaces in
homes, churches, schools, and other similar areas, where they
might come in contact with people and pets.
Prevention
• When traveling abroad, avoid direct contact with wild animals and
be especially careful around dogs in developing countries. Rabies
is common in developing countries in Asia, Africa, and Latin America
where dogs are the major reservoir of rabies. Tens of thousands of
people die of rabies each year in these countries. Before traveling
abroad, consult with a health care provider, travel clinic, or your
health department about the risk of exposure to rabies, preexposure prophylaxis, and how you should handle an exposure,
should it arise.
• Pre-exposure vaccinations are intended for high risk people, such
as: veterinarians, lab workers, animal handlers, wildlife officers,
those who are in contact with rabid bats, skunks, raccoons, cats,
dogs or other species at risk of having rabies and international
traveler.
• Note: people at high risk should have a blood sample tested every
six months and receive a booster vaccine (when necessary), in
addition to a pre-exposure vaccine.
Treatment
• There is no treatment for rabies after symptoms of the
disease appear. However, two decades ago scientists
developed an extremely effective new rabies vaccine
regimen that provides immunity to rabies when
administered after an exposure (post-exposure
prophylaxis) or for protection before an exposure occurs
(preexposure prophylaxis). Although rabies among
humans is rare in the United States, every year an
estimated 18,000 people receive rabies preexposure
prophylaxis and an additional 40,000 receive postexposure prophylaxis.
Treatment
Preexposure prophylaxis
• Preexposure vaccination is recommended for persons in
high-risk groups, such as veterinarians, animal handlers,
and certain laboratory workers. Other persons whose
activities bring them into frequent contact with rabies
virus or potentially rabid bats, raccoons, skunks, cats,
dogs, or other species at risk of having rabies should
also be considered for preexposure prophylaxis. In
addition, international travelers likely to come in contact
with animals in areas of enzootic dog rabies which lack
immediate access to appropriate medical care, including
biologics, should be considered for preexposure
prophylaxis.
Treatment
Post-exposure prophylaxis
• Post-exposure prophylaxis (PEP) is indicated for persons possibly
exposed to a rabid animal. Possible exposures include animal
bites, or mucous membrane contamination with infectious tissue,
such as saliva. {For more information on types of exposures, PEP
should begin as soon as possible after an exposure. There have been
no vaccine failures in the United States (i.e. someone developed
rabies) when PEP was given promptly and appropriately after an
exposure.
• Administration of rabies PEP is a medical urgency, not a medical
emergency. Physicians should evaluate each possible exposure to
rabies and as necessary consult with local or state public health
officials regarding the need for rabies prophylaxis.
• In the United States, PEP consists of a regimen of one dose of
immune globulin and five doses of rabies vaccine over a 28-day
period. Rabies immune globulin and the first dose of rabies vaccine
should be given as soon as possible after exposure. Additional doses
of rabies vaccine should be given on days 3, 7, 14, and 28 after the
first vaccination. Current vaccines are relatively painless and are given
in your arm, like a flu or tetanus vaccine.
Treatment
Summary
• No treatment for rabies after symptoms of disease appear.
• Quarantine and/or vaccination to eradiate disease.
• Wash wound with a special substance containing anti-rabies serum
and water.
• Get a post-exposure prophylaxis injection of HRIG, human rabies
immune globulin.
• Follow up with the recommended subsequent treatment, which is to
receive five. injections of HDCV, human diploid cell vaccine.
• Sometimes Hyper-immune serum globulin is used in addition.
• Note: Immediate treatment after exposure is important, as well as,
maintaining post-exposure prophylaxis.
Sources
• Images
http://www.vet.ksu.edu/depts/rabies/images/rabstruc.jpg
http://www.visualsunlimited.com/results.jsp
http://www.cdc.gov/ncidod/dvrd/kidsrabies/Statistics/stats.htm
• CDC
http://www.cdc.gov/ncidod/dvrd/rabies/
• Yahoo Health
http://health.yahoo.com/ency/healthwise/hw181108;_ylt=AmvLeHDlbgVyLgmqnogs2J0Su7cF
• Textbook