Case study: VIROLOGY
▪ Patient: Jude Martin; Male, 9-year-old
▪ Patient history: (stray) dog bite while playing at the public people’s park 2 months ago
▪ Signs & symptoms developed: nausea and vomiting. In less than a week, he became
anxious and had a fever of 39.9°. He
became more anxious and often hallucinates. He shoves off and refuses to drink water
with his medicine His conditions
continues to deteriorate and he started salivating with difficulty of breathing.
▪ Patient died 2 weeks after admission
1.Which of the clinical features that Jude is manifesting suggest rabies?
Prodromal period phase: nausea and vomiting and fever of 39.9 °
Acute neurologic phase: patients show signs of nervous system dysfunction such as
nervousness, hallucinations, hydrophobia (fear of water), increased salivation and
difficult in breathing.
Reference: Brooks, G. F., Jawetz, E., Melnick, J. L., & Adelberg, E. A. (2013). Jawetz,
Melnick & Adelberg's medical microbiology (26th edition.). New York : London: McGraw-
Hill Medical. Page 622
2. How long is the incubation period (disease progression) of rabies following
animal bite? Explain why.
The incubation period in humans is typically 1–3 months but may be as short as 1 week
or more than a year. It is usually shorter in children than in adults. The clinical spectrum
can be divided into three phases: a short prodromal phase, an acute neurologic phase,
and coma.
•The prodrome, lasting 2–10 days, may show any of the following nonspecific
symptoms: malaise, anorexia, headache, photophobia, nausea and vomiting, sore
throat, and fever. Usually there is an abnormal sensation around the wound site.
• Acute neurologic phase, which lasts 2–7 days, patients show signs of nervous
system dysfunction such as nervousness, apprehension, hallucinations, and bizarre
behavior. General sympathetic overactivity is observed, including lacrimation, pupillary
dilatation, and increased salivation and perspiration. A large fraction of patients will
exhibit hydrophobia (fear of water) or aerophobia (fear when feeling a breeze). The act
of swallowing precipitates a painful spasm of the throat muscles.
• This phase is followed by convulsive seizures or coma and death. The major cause of
death is cardiorespiratory arrest. Paralytic rabies occurs in about 30% of patients, most
frequently in those infected with bat rabies virus. The disease course is slower, with
some patients surviving 30 days. Recovery and survival are extremely rare.
•The usual incubation period in dogs ranges from 3 to 8 weeks, but it may be as short
as 10 days. Clinically, the disease in dogs is divided into the same three phases as
human rabies.
Reference: Brooks, G. F., Jawetz, E., Melnick, J. L., & Adelberg, E. A. (2013). Jawetz,
Melnick & Adelberg's medical microbiology (26th edition.). New York : London: McGraw-
Hill Medical. Page 622
3. How is rabies infection confirmed? When is rabies antibody detected in a usual
rabies disease?
• Rabies Antigens or Nucleic Acids
Tissues infected with rabies virus are currently identified most rapidly and accurately by
means of immunofluorescence or immunoperoxidase staining using anti-rabies
monoclonal antibodies. A biopsy specimen is usually taken from the skin of the neck
at the hairline. Impression preparations of brain or cornea tissue may be used.
A definitive pathologic diagnosis of rabies can be based on the finding of Negri bodies in
the brain or the spinal cord. They are sharply demarcated, more or less spherical, and
2–10 μm in diameter, and they have a distinctive internal structure with basophilic
granules in an eosinophilic matrix. Negri bodies contain rabies virus antigens. Both
Negri bodies and rabies antigen can usually be found in animals or humans infected
with rabies, but they are rarely found in bats.
Reverse transcription-polymerase chain reaction testing can be used to amplify parts of
a rabies virus genome from fixed or unfixed brain tissue. Sequencing of amplified prod-
ucts can allow identification of the infecting virus strain.
• Serum antibodies to rabies can be detected by immunofluorescence or
neutralization tests. Such antibodies develop slowly in infected persons or animals
during progression of the disease but promptly after vaccination with cell- derived
vaccines. Antibodies in cerebrospinal fluid are produced in rabies-infected individuals
but not in response to vaccination.
• Viral isolation
Available tissue is inoculated intracerebrally into suckling mice. Infection in mice results
in encephalitis and death. The central nervous system of the inoculated animal is
examined for Negri bodies and rabies antigen. In specialized laboratories, hamster and
mouse cell lines can be inoculated for rapid (2- to 4-day) growth of rabies virus; this is
much faster than virus isolation in mice. An isolated virus is identified by fluorescent
antibody tests with specific antiserum. Virus isolation takes too long to be useful in
making a decision about whether to give vaccine.
• Animal Observation
All animals considered “rabid or suspected rabid” should be sacrificed immediately for
laboratory examination of neural tissues. Other animals should be held for observa- tion
for 10 days. If they show any signs of encephalitis, rabies, or unusual behavior, they
should be killed humanely and the tissues examined in the laboratory. If they appear
normal
after 10 days, decisions must be made on an individual basis in consultation with public
health officials.
Reference: Brooks, G. F., Jawetz, E., Melnick, J. L., & Adelberg, E. A. (2013). Jawetz,
Melnick & Adelberg's medical microbiology (26th edition.). New York : London: McGraw-
Hill Medical. Page 622-623
4. Explain the postexposure rabies immunization. (How it works)
Postexposure prophylaxis (PEP) consists of a dose of human rabies immune
globulin (HRIG) and rabies vaccine given on the day of the rabies exposure, and then
a dose of vaccine given again on days 3, 7, and 14. For people who have never been
vaccinated against rabies previously, postexposure prophylaxis (PEP) should always
include administration of both HRIG and rabies vaccine. The combination of HRIG and
vaccine is recommended for both bite and non-bite exposures, regardless of the interval
between exposure and initiation of treatment.
The decision to administer rabies antibody, rabies vaccine—or both—depends on
several factors:
(1) the nature of the biting animal (species, state of health, domestic or wild) and its
vaccination status.
(2) the availability of the animal for laboratory examination (all bites by wild animals and
bats require rabies immune globulin and vaccine).
(3) the existence of rabies in the area.
(4) the manner of attack (provoked or unprovoked);
(5) the severity of the bite and contamination by saliva of the animal; and
(6) advice from local public health officials. Schedules for postexposure prophylaxis
involving the administration of rabies immune globulin and vaccine are available from
the Centers for Disease Control and Prevention and state public health offices.
Reference: Reference: Brooks, G. F., Jawetz, E., Melnick, J. L., & Adelberg, E. A.
(2013). Jawetz, Melnick & Adelberg's medical microbiology (26th edition.). New York :
London: McGraw-Hill Medical. Page 624-625
Retrieve April 19,2021 at https://www.cdc.gov/rabies/medical_care/index.html
5. Which between inactivated vaccine and live vaccine is preferrably used for the
following immunizations?
5.a rabies- live, attenuated vaccine
5.b influenza- live, attenuated vaccine
5.c tetanus-inactivated vaccine
Reference:Retrieve April 19,2021 at
https://www.cdc.gov/vaccines/pubs/pinkbook/downloads/prinvac.pdf
6. Prepare an anti-rabies information drive for the community (poster, lecture,
leaflet, flyer, broadcast, or any relevant
process) - to be explained/played/broadcasted during the case presentation)
