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1. ‘Veterinary Epidemiology &
Zoonoses’
VPH-321
(Credit Hours-2+1)

2. Rabies/Lyssa/ Hdrophobia

3. Introduction
It is an acute fatal disease in man & other warm blooded animals
Characterized by:
Abnormal behavior,
Nervous disturbances such as motor nerve irritability,
Mania,
An attacking complex,
Inability to swallow,
Excessive salivation,
Impairment of consciousness,
Progressive ascending paralysis &
Death due to respiratory paralysis

4. • Rabies claims nearly 55000 human deaths, worldwide
• Mostly children
• Presently the efforts at rabies control have enabled a marginal
reduction of rabies deaths from 30,000 to 20,000 in India annually
Introduction

5. Lyssa virus
Family: Rhabdoviridae
RNA virus,
Bullet shaped (180 nm X 75 nm in dia.)
Highly fragile viruses
susceptible to standard disinfectants
Sunlight & moderate heat destroy the virus
There are 25 viruses in this genus, of which closely related rabies
viruses are called “Classical rabies viruses”
Etiology

6. Serotypes of rabies viruses are:
1. Lagos bat virus,
2. Mokola virus,
3. Duvenhage virus,
4. European bat lyssa virus I (EBL I),
5. European bat lyssa virus II (EBL II) &
6. Australian bat lyssa virus
Etiology

7. • Based on antigenicity, the virus is classified as fixed or street rabies
virus
Etiology
Sl. No. Fixed rabies virus Street rabies virus
1. The virus is passaged by serial
intradermal route in rabbits
It is from naturally occurring infection
2. Incubation period is fixed and shorter
(6-7 days)
Incubation period is variable (11-47
days)
3. It does not produce Negri bodies It produces Negri bodies
(Intracytoplasmic inclusion bodies)
4. No shedding of virus in the saliva Shedding of virus in the saliva
5. The virus is not virulent and self-
limiting. Used for vaccine production.
The virus is virulent and not self-
limiting. Pathogenic to warm blooded
animals.

8. • Worldwide distribution
• Primary reservoirs:
Foxes, bats, raccoons, skunks, dogs, cats & cattle
• Transmission:
From fresh saliva via bite, scratch or abrasion by an rabid animal
Rabid dogs shed virus in saliva 5-7 days before showing signs
Cat does so for only 3 days before signs
Contamination of skin wounds by fresh saliva from infected animals
also a source of infection
Source & Transmission

9. • Central nervous system disturbances
• The clinical course especially (in dogs)
• Can be divided into 3 phases:
▫ The prodromal form
▫ The excitative form
▫ The paralytic form
Prodromal period: 1-3 days, animals either show signs of paralysis
or become vicious
Disease in animals

10. 1. In dogs
Furious form (changes in behaviour & stage of
excitement)
 Tendency to bite either inanimate/animate objects
till death
 Travel to long distance
 Shows imaginary catching stance
 Attempt to lick water but unable to drink water due
to the paralysis of pharyngeal & laryngeal muscles
 Drooling of saliva
 Photophobia
 Changes in barking due to paralysis of vocal chords
 Finally, dropped jaw & tongue will protrude & head
will drop down
Disease in animals

11. 1. In dogs
Dump form or paralytic form:
Isolated themselves in dark places
Paralysis of lower jaw (dropped jaw ), tongue, larynx &
hindquarters
Not capable to bite
2. In cats
Furious form is more common
Disease in animals

12. 3. In cattle
Furious form is more common:
Violently attack other animals or
Attack to inanimate objects,
loud bellowing,
Incoordination of gait,
Excessive salivation,
Behavioral changes,
Muzzle tremor,
Aggression,
Sexual excitement,
Hyper excitability &
Pharyngeal paralysis
Disease in animals
Paralytic form:
 Knuckling of hind fetlock,
Sagging & swaying of hind
quarter while walking,
 Deviation of tail to one side,
 Drooling of saliva & yawing
movement

13. • In sheep:
Hyperexcitability,
salivation,
vocalization,
recumbency,
vigorous wool plucking,
excessive bleating does not occur but continuous bleating is
common & starring of eyes & twitching of lips
Disease in animals

14. • In horse:
Muscle tremors are frequent & common,
pharyngeal paralysis,
ataxia & lethargy,
Sudden onset of lameness in one limb followed by recumbency &
violent head tossing
• In pigs:
Twitching of nose,
excessive salivation,
chronic convulsion,
rapid chewing movement & may walk backward
Disease in animals

15.  The incubation period: few months (usually 30 to 60 days),
 Depending on
 The distance of bite,
 Severity of bite,
 Amount of virus inoculated
 Aggressive status of the rabid animal
 Infection reaches to CNS symptoms begin to show
 The infection is effectively untreatable & usually fatal within days
 Death almost invariably results 2-10 days after first symptoms
 Drinking cause extremely painful laryngeal spasm
 Patient refuses to drink (hydrophobia-fear of water)
 Muscle spasm, laryngospasm & extreme excitability are present
Disease in human

16.  Convulsions occur
 Thick tenacious saliva
 Increased lacrimation,
 Frequent micturition
 Increased perspiration.
 The initial symptoms of rabies are often mild fever & pain or paresthesia
at the wound site
 Furious rabies is rapidly fatal: hydrophobia or aerophobia, phobia
towards sound, hyperactivity and fluctuating consciousness
 Flaccid paralysis ascending with pain in the affected muscles & mild
sensory disturbances will precede death from respiratory paralysis
Disease in human

17. Classification of exposure based involvement
of risk
Class I-
 Slight or negligible risk
 Licks on healthy/ unbroken
skin
 Scratches without oozing of
blood
Class II-
 Definite but moderate risk
 Consumption of unboiled milk from
suspected animals
 Licks on fresh cuts
 Scratches with oozing of blood
 All bites except on head, neck, face, palm
and fingers
 Minor wounds less than five in number
Class III-
 Severe/ grave risk
 Licks on mucosa
 Bites on head, Neck, face,
palm & fingers
 Lacerated wounds on any
part of the body
 Bites from wild animals

18. 1. Sign & symptoms
2. Fluorescent antibody test (FAT)
▫ Corneal impression smear, as well as brain
▫ Highly specific & rapid test (99.9%)
▫ Detects different strains using monoclonal antibody
▫ The identifiable strains correlate well with species & geographic
distributions observed
3. Identification of Negribodies (intracytoplasmic inclusion bodies) in the
brain impression smear by Seller's staining technique
4. Virus isolation from body fluid or brain tissue
5. Molecular techniques
Diagnosis
Negri bodies

19. Post-exposure care to prevent rabies includes:
Washing & scrubbing the wound with phenolic soap and/or plenty of
running tape water
Application of antiseptics
Avoiding bandaging or suturing of wound, or point of contact
Administering anti-rabies immunizations as soon as possible
Anti-rabies vaccine should be given for category II & III exposures
(follow post exposure schedule)
Treatment

20. • Post exposure schedule
 If the animal is not previously immunized,
 Post exposure vaccination on
0-day (the day starts within 24 hours after bite), 3rd
, 7th
, 14th
, 28th
& if
necessary, on 90th
day (Essen's schedule)
 If the animal is immunized annually 0 day, 3rd
and 7th
day, put the
animal under observation for 10 days
 If the animal dies, should follow the full regimen (5 doses)
Treatment

21. Pre-exposure schedule
• Type of vaccine:
Inactivated (from cell culture or embryonated egg vaccine)
• Number of doses:
Three: 0, 7th
& 21st
or 28th
day given by IM or ID route (vaccine should not
be given in the gluteal region)
Booster: After one year then every five years
• Contraindication:
Severe reaction to previous dose
• Adverse reactions:
Mild local or systemic reactions; rare neuroparalytic reactions reported
• Special precautions:
Do not use animal-brain-derived vaccines
Vaccination

22. • Postexposure immunization:
Upto 50% of human rabies immune globulin is infiltrated around the
wound; the rest is administered IM
(ERIG or HRIG: anti-rabies antibody)
• Human Diploid Cell Vaccine (HDCV):
5 injections IM at days 0, 3, 7, 14, & 28
• Vaccination of domestic animals
• Enforced animal control measures (Animal Birth Control and Anti-
rabies vaccination programme: ABC-AR)
• Controlling stray dog population
• Proper immunization of household dogs (ABC-AR programme)
• Vaccination of high risk personnel
• Awareness programme among public
Prevention