RABIES
(Hydrophobia, Lyssa)
Rabies is a viral zoonotic neuroinvasive disease that causes acute encephalitis in
mammals. It is generally characterized by CNS irritation, paralysis, and death.
Animals causing rabies can be classified into two. Canine rabies is caused by domestic
animals while sylvatic rabies is caused by wild animals.
Once symptoms of the disease develop, rabies is fatal. In the Philippines, around 300
to 600 Filipinos die every year.
History-Cultural impact
Because of its potentially violent nature, rabies has been known since 3000 B.C. The
term "rabies" is possibly derived from the Sanskrit word "rabhas" or "to do violence". The
Greeks derived the word "lyssa" meaning "lud" or "violent", this terminology is used in the
name of the genus of rabies lyssavirus.
In the 19th century rabies has been considered a scourge for its prevalence. Louis
Pasteur was then able to test post-exposure treatments in 1895. It was not until 1960 when
the virus itself was isolated.
Epidemiology
Etiology
The virus that causes rabies is a rhabdovirus of the genus Lyssavirus.
Incubation Period
From 2 to 8 weeks up to a year depending on the following:
• Site of the wound
• Severity of the wound
• Amount of virus introduced
• Protection provided by clothing
Pathophysiology
Rhabdovirus
Penetration to tissue
Travels along peripheral nerves
CNS
Body tissue
Clinical Manifestations
Rabies is a highly neurotropic virus that evades immune surveillance by its
sequestration in the nervous system. Upon inoculation, it enters the peripheral nerves. A
prolonged incubation follows, the length of which depends on the size of the inoculum and its
proximity to the CNS. Amplification occurs until bare nucleocapsids spill into the myoneural
junction and enter motor and sensory axons. At this point, prophylactic therapy becomes
futile, and rabies can be expected to follow its fatal course, with a mortality rate of 100%.
The rabies virus travels along these axons to enter the spinal ganglion. Its
multiplication in the ganglion is heralded by the onset of pain or paresthesia at the site of the
inoculum, which is the first clinical symptom and a hallmark finding. From here, the rabies
virus spreads quickly into the CNS, and spread is marked by rapidly progressive encephalitis.
Thereafter, the virus spreads to the periphery and salivary glands.
Signs and Symptoms
I. Incubation period
o
The rabies virus transfers from peripheral areas to the CNS.
o
The infected individual remain asymptomatic.
o
The average duration of incubation is 20-90 days.
o
The rabies virus is segregated from the immune system during this period, and no
antibody response is observed.
II. Prodromal period
o
The virus enters the CNS.
o
The duration of this period is 2-10 days.
o
Paresthesia or pain at the inoculation site and hydrophobia are pathognomonic for
rabies and occurs in 50% of cases during this phase.
o
Symptoms may include malaise, anorexia, headaches, fever, chills, pharyngitis,
nausea, emesis, diarrhea, anxiety, agitation, insomnia, and depression.
III.Acute neurologic period
o
This period is associated with objective signs of developing CNS disease.
o
The duration is 2-7 days.
o
Furious rabies may develop in this period. Patients develop agitation, hyperactivity,
restlessness, thrashing, biting, confusion, or hallucinations. Episodes may be triggered
by visual, auditory, or tactile stimuli or may be spontaneous. Seizures may occur. This
phase may end in cardiorespiratory arrest or may progress to paralysis.
o
Paralytic rabies is also known as dumb rabies or apathetic rabies because the patient
is relatively quiet compared with a person with the furious form.
IV. Coma
o
This begins within 10 days of onset; the duration varies.
o
Without intensive supportive care, respiratory depression, arrest, and death occur
shortly after coma.
Diagnosis
Observations of the presenting clinical manifestation and providing a history taking
generally provides the basis for diagnosing rabies. However, for clarification purposes,
Fluorescent Antibody Technique is used to demonstrate the Rabies viral antigens in infected
cells that is usually done ante mortem by obtaining sample from the CSF.
o
Negri Bodies
Negri bodies ae cytoplasmatic inclusion bodies found in the purkinje cells of the brain
in cases of rabies. Negri's bodies are important because their presence make possible a
positive diagnosis of rabies.
Dr. Adelchi Negri reported the identification of what he believed to be the etiologic
agent of rabies, the Negri body. In his report, he described Negri bodies as round or oval
inclusions within the cytoplasm of nerve cells of animals infected with rabies.
Treatment
Treatment of humans consists of thorough flushing and cleansing of the bite wound
with soap and water to be followed by introduction of vaccines.
o
Post-exposure treatment
Post-exposure treatment is given to persons who are exposed to rabid animals. It consists
of local wound treatment, active immunization (vaccination) and passive immunization
(administration of rabies immunoglobin).
o
Active and passive immunization
Active immunization or vaccination aims to induce the body to develop antibodies against
Rabies whose effect lasts for 1 to 3 years.
Passive immunization is the process of giving an antibody to persons with Category III
exposure (head and neck bites, multiple/single deep bites, contamination of mucous
membranes, licks of the eyes, lips and mouth) in order to provide immediate protection
against Rabies, which should be administered within the first seven days of active
immunization. The effect of the immunoglobulin is only short term.
o
Immunization schedule
Grade of
exposure
I
Type of exposure
Contact with a rabid
suspected rabid animal
Immunization schedule
or Contact with an
inoculated animal
Touching/feeding
animal,
Touching
but no contact with saliva;
inoculated lure,
and skin undamaged prior to
skin intact
and during contact
No
immunization
necessary
If
uncertainty exists than schedule B is to
be followed.
II
a) Animal has nibbled or
licked exposed skin.
b) Contact with saliva
c) Superficial, non- bleeding
scratches made by the
animal
Touching
inoculated lure,
skin damaged.
Immediate immunization according to
schedule B. In case of uncertainty
concomitant prophylaxis as specified in
schedule C. If animal is examined &
found to be non-rabid then continue as
in schedule A
III
a) All bites
b) Bleeding scratches
c) All scratches on the head,
neck, scapular region, arm &
hands
d) Contact of animal saliva
with mucous membrane of
patient
Contact of
inoculated lure
with mucous
membrane or fresh
skin wound
Immediate concomitant prophylaxis per
schedule C. If animal is proved non-rabid
it is adjustable to continue treatment as
in schedule A.
Schedule A
Schedule B
Schedule C
Prophylactic
immunization prior
to exposure.
Immunization after
exposure.
Concomitant prophylaxis after exposure.
Rabipur® as in schedule B + 1 X 20 I.V./kg body wt.
One injection IM on days
One injection IM on
human rabies immunoglobulin concomitantly with
0,3,7,14,30
&
if
days 0,7,28 and 365
injection of Rabipur or on day 7 after the first injection
necessary on day 90.
of Rabipur® at the latest.
Nursing Responsibilities
•
Wound cleaning
•
Medication- antibiotic, anti-tetanus
•
Control circulatory and CNS damage
•
Patient isolation/transmission
Prevention

Education

Animal Control

Vaccination

Proper surveillance
National Rabies Prevention & Control Program
Goal: Human Rabies is eliminated in the Phil. And the country is declared rabies-free
Objectives:
a. Human Rabies: reduce incidence from 7/mil to 1/mil by 2010 & eliminate by 2015
b. Canine Rabies: reduce from 70/100,000 to 7/100,000 by 2010 & eliminate by 2015
Key facts

Rabies is widely distributed across the globe. More than 55 000 people die of rabies
each year. About 95% of human deaths occur in Asia and Africa.

Most human deaths follow a bite from an infected dog. Between 30% and 60% of the
victims of dog bites are children under the age of 15.

Wound cleansing and immunizations, done as soon as possible after suspect contact
with an animal and following WHO recommendations, can prevent the onset of rabies
in virtually 100% of exposures.

Once the signs and symptoms of rabies start to appear, there is no treatment and the
disease is almost always fatal.

Globally, the most cost-effective strategy for preventing rabies in people is by
eliminating rabies in dogs through animal vaccinations.

March is Rabies Awareness Month and September 28 is World Rabies Day!
JORA MARJORIE M. DIMAYUGA