Epidemiology prevention and control of rabies - lecture notes for MBBS students. preventive and social medicine/ community medicine

1. Epidemiology, Prevention & Control
of
Rabies
Dr Tushar Patel
M -9879576350
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2. Introduction
• The rabies virus (RABV)
– family Rhabdoviridae
– genus Lyssavirus
– SS RNA (-) (enveloped)
– Several different lyssaviruses throughout world
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3. Introduction
• So viral copy errors occur during RNA
replication
• Lyssavirus like other RNA viruses lack proof-
reading enzymes
• Due to drift, different variants arise
• Several different lyssaviruses serve as major
etiological agent throughout world
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4. Introduction
Due to encephalomyelitis
• First stage – Generalized Symptoms
• Second stage – Excitability, Painful swallowing, spasm of
swallowing muscles after contact with water/(air) leads to
Hydrophobia,(aerophobia)
• Third stage – paralytic stage –respiratory paralysis,
asphyxia, death.
• Diagnosis – post mortem brain tissue – F.A. on staining
Virus isolation in mouse or cell culture
• 100% case fatality rateFirst read lecture on Hepatitis A and
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5. Epidemiology
Reservoir / source of infection
Mode of transmission
Susceptible Host
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6. Reservoirs of infection
Reservoir : wild and domestic animal
Wild canidae (dog like carnivorous)-
• India: Mongoose
• Africa and Asia: Jackals
• Central and south America: Vampire Bat
• North America: Foxes
• Middle East: wolves
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7. Reservoir of infection
Domestic animals
• Mammals are important hosts
• Dogs are the source of most human rabies
deaths in the Asia and africa
• Bats are the source of most human rabies
deaths in the north and south America,
Europe, Australia.
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8. Reservoir of infection
• Different viral variants are compartmentalized
within particular wild host (closed cycle)
• Virus perpetuate and persists for decades or
longer in closed cycle within same species
• Spillover infection: infection to different species
(Ex. domestic animal/human) dead end.
– Transmit infection to other before death
• Wild Rabid animals: Excrete virus for greater
period before appearance of signs and live longer
after appearance of signsFirst read lecture on Hepatitis A and
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9. Reservoir of infection
• Period of Communicability:
– In dogs and cats – 3-7 days before onset of clinical
signs and throughout course of disease.
– If healthy domestic animal bite a person, observed
for 10 days
• Infective material/source of infection:
– Saliva of rabid animal
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10. Modes of transmission
• Human infection usually occurs following a
trans-dermal bite or scratch by an infected
animal.
• Transmission can also occur when infectious
material – usually saliva – comes into direct
contact with human mucosa or fresh skin
wounds
• Saliva --- bite --- virus nervous system --- brain -
encephalitis First read lecture on Hepatitis A and
Typhoid for basic concepts

11. • Human-to-human transmission by bite is
theoretically possible but has never been
reported
• Rarely, by exposure to mucus membrane of
aerosol, inactivated vaccine or by organ
transplantation
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12. Host Factors
• Immunity – all mammals are susceptible.
developing immunity???
• Occupation: Veterinarians, animal handlers,
wildlife officers, persons working with viruses
in laboratories
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13. • Incubation period: usually 3-8 weeks
– Rarely 9 days or 7 years
– Highly variable - depends on site (nerve supply and
distance from brain) and severity of wound, amount and
strain of virus First read lecture on Hepatitis A and
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14. Prevention
• Controlling reservoir
– Early diagnosis & treatment - #
– Elimination/Isolation/ Vaccination of animals - √
• Interrupting transmission #
–
• Protecting host
– Immuno-prophylaxis √
– Chemoprophylaxis √
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15. • Elimination of dogs
–Most logical and cost effective
–ownerless animals and strays – Sacrifice
• Not pet dogs/cats
• Wild-life animal - Focal depopulation
–In circumscribed enzootic area near human
habitations, fox, shunk, racoon, etc. can be
reduced
–Large forest -difficult
–how ????
• Sterilization
• Sacrifice
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16. Restriction of movement/detention
Mass vaccinations of dogs
–has reduced the number of human (and
animal) rabies cases in several countries
–However, recent increases in human rabies
deaths in parts of Africa, Asia and Latin
America suggest that rabies is re-emerging
as a serious public health issue
–After bite – vaccine required?
–Immunization of wildlife animal reservoir
• Oral immunization using air-drops of bait
containing vaccine has eliminated rabies in
some part of Europe
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17. Vaccinations of dogs
–Pet dogs
–Details – veterinarians
– It is recommended to vaccinate
puppies at 3 months of age, then at
9 months of age and revaccinate
annually.
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18. Prevention
• Healthy dog/cat known to have bitten a person
– Detain and observe for 10 days
• If pet/zoo animal and normally behaving
– Quarantine for 3-12 weeks
– If signs for rabies – sacrifice
• Unimmunized dog/cat bitten by rabid animal
– Immediately sacrifice
– If pet/zoo animal and detention is selected
• For 6 months, vaccine 1 month before release
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19. Clinical features in dog
• Change in behaviour and excitability/paralysis
followed by death
– biting without any provocation
– eating abnormal items such as sticks, nails,etc.
– running for no apparent reason
• a change in sound e.g. hoarse barking or inability
to make a sound
• excessive salivation / foaming at the angles of the
mouth – but not hydrophobia (fear of water).
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20. Prevention
Protection of host
–Chemo-prophylaxis (Local treatment)
–Immuno-prophylaxis
• Active
–Post-exposure prophylaxis
–Pre-exposure
• Passive
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21. • Is simply observing the biting dog or cat for 10
days without starting treatment justified?
Why?
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22. • No.
• it is compulsory to start treatment and keep
the biting dog/cat under 10 days of
observation.
• If the animal remains healthy during the
observation period then post-exposure
prophylaxis (PEP) can be converted into pre-
exposure regimen
First read lecture on Hepatitis A and
Typhoid for basic concepts

23. Categories of contact
with suspect rabid animal
Post-exposure
prophylaxis measures
Category I – touching
or feeding animals,
licks on intact skin
None
Category II –
nibbling of
uncovered skin,
minor scratches or
abrasions without
bleeding
Vaccination + Local
treatment of wound
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24. Categories of contact with
suspect rabid animal
Post-exposure prophylaxis
measures
Category III – licks on
broken skin;
contamination of
mucous membrane
with saliva from licks,
single or multiple
transdermal bites or
scratches, contacts with
bats.
Vaccination +
Immunoglobulin +
Local treatment of
wound
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25. • Bites especially on the head, neck, face, hands
and genitals are category III exposures
because of the rich innervation of these areas.
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26. Local treatment/chemoprophylaxis
• How does one treat an animal bite?
• Local treatment
– What should be done?
– What should not be done?
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27. • This is the most effective first-aid treatment
against rabies.
• Wounds should be washed and flushed
immediately with soap and water for 10–15
minutes.
– If soap is not available, flush with water alone.
• Wounds should be cleaned thoroughly at the
health care facility with 70% alcohol or
povidone-iodine.
First read lecture on Hepatitis A and
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28. • Tetanus Toxoid
• Antibiotics
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29. Avoid:
• Covering the wound with dressings or bandages.
• Suturing which facilitates further inoculation of
rabies virus.
—— If necessary for closing large wounds,
suturing should be done after local infiltration of
wound with rabies immunoglobulin (RIG).
—— suture should be loose and not interfere
with free bleeding and drainage
First read lecture on Hepatitis A and
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30. Vaccination
• Production and use of nerve-tissue vaccines
be discontinued as soon as possible and
replaced with CCEEVs.
Cell culture Vaccine (verorab) (Abhayrab)
Embryonated egg-based(Rabipur)
• Type: Killed/inactivated (lyophilized)
• Preparation: Human Diploid Cell; Chick
embryo (0.4% NaCl)
• Storage: 2-8o C First read lecture on Hepatitis A and
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31. • Mention dose, site, route and no. of doses of
vaccination.
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32. • Dose: Verorab CCV IM 0.5 ml ID 0.1 ml
Rabipur EEV IM 1 ml ID 0.1 ml
• No Of Doses:
Pre-exposure 0, 7, 28 (IM preferred)
Post-exposure 0, 3, 7, 14, 28
Post-exposure ID 0, 3, 7, 28 (ID always at 2 sites)
Prev Vaccinated 0, 3
Prev Vaccinated ID 0, 3 (ID always at 2 sites)
Zagreb regimen 0 7 21 (2-1-1) IMFirst read lecture on Hepatitis A and
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33. • Site: > 2 years – insertion of deltoid
< 2 years -- antero-lateral aspect of thigh
• Route: IM, Intra-dermal recommended to reduce
the cost - (provided number of cases are more)
• 0,3,7,28,90* 0.1 ml
• Vaccine administered intra-dermally must raise a visible
and palpable “bleb” in the skin
• *CDC manual First read lecture on Hepatitis A and
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34. AEFI:
• 35–45% of vaccinees, minor and transient
erythema, pain and/or swelling may occur at the
site of injection (occasionally G.B. Syndrome)
Contraindications and Precautions:
• For pre-exposure prophylaxis:
–Previous severe reaction to vaccine
• Hypersensitivity reaction – generalized rash, urticaria,
arthritis, arthralgia, angioedema etc
• Anti-histamines, give differently prepared vaccine.
• For post-exposure prophylaxis:
–No contraindication as Rabies is lethal
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35. • Efficacy:
–Almost invariably effective
• Duration of immunity:
–Long lasting memory
–Anamnestic response
– Enhanced reaction of body’s immune system to antigen
which was previously encountered.
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36. Immunoglobulin
• Indication
– Category III and Category II immuno-deficient
• Preparations
– Human IG
• Preferred
–Because Slow clearance
• Frequently unavailable
– Equine IG
• If Human IG not available
–Because Fast Clearance
• small risk of anaphylactic reaction -1/45000
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37. immunoglobulin
Dose: Human: 20 IU/kg Equine: 40 IU/kg
No of Dose: Single on 0 day
Site: as much as possible into/around wound site/sites
While infiltrating RIG into bite wounds, care must be
taken to avoid injecting into blood vessels and nerves.
Route: IM at distant site (remaining)
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38. Immunoglobulin
• RIG should preferably be administered
simultaneously with the anti-rabies
vaccination. (at different site)
• It should, however, never be administered
later than 7 days after start of vaccination as it
then will suppress native antibody production.
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39. immunoglobulin
• In small children with multiple bites, if the
volume is insufficient for infiltration in and
around all wounds, RIG should be diluted with
sterile normal saline to double or three times
the volume.
First read lecture on Hepatitis A and
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40. Pre-exposure prophylaxis
• Veterinarians, animal handlers, wildlife
officers, persons working with viruses in
laboratories... at permanent risk of exposure
to rabies should have:
• General public do not require booster/pre-
exposure vaccination
• 0,7,28 day
• one serum sample taken every six months
• a booster dose when the titer falls below 0.5
IU/ml
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41. Previously Vaccinated
• Vaccination on 0, 3,7 day (IM/ID)*
• Local treatment of wound
• No RIG should be applied
• * if Ab titer high/cat II – two doses 0,3
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42. • 0,3,7,14,28
• 0,3,7,28,90
• 0,7,28
• 0,3,7
First read lecture on Hepatitis A and
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43. Control
• Controlling reservoir
– Early diagnosis & treatment - #
– Isolation/ Elimination/ Vaccination of dogs - √
– Isolation precautions during treatment
– Tracing Contacts
– Tracing source of infection
• Interrupting transmission #
–
• Protecting host
– Immuno-prophylaxis √
– Chemoprophylaxis √
First read lecture on Hepatitis A and
Typhoid for basic concepts

44. Control
– Contact isolation for respiratory secretions/saliva
• If Exposed than anti-rabies treatment
– Search for people and other animal bitten
– Search for rabid animal
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45. • If person is bitten by a rat do I require post-
exposure prophylaxis (PEP)?
• What should be done if person is bitten by a
bat?
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46. • It is not necessary to take PEP in bite cases by
house rats.
• However, it is prudent to take PEP when bitten
by wild rats/rodents.
• there are reports of sero-positivity against bat
rabies virus in the bat population in Thailand.
Therefore, it is recommended to take PEP
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47. • If bitten by another animal like monkey?
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